Performing Bench Work (Basic)

Information Sheet 5.1.1: Layout tools

Surface Gauge
A surface gage is used for many purposes, but is most often used for layout work (figure 5.27).
The surface gage can be used to scribe layout lines at any given distance parallel to the work
surface.

fig. 5.26

fig. 5.27

Vernier Height Gauge

The vernier height gauge is a development of the
vernier caliper. The graduated frame is held in the
vertical position by being attached to an accurately
ground base.

The vernier is read in the same way as the vernier
calipers, except that the readings would be taken from
the movable jaw to the base.

The height gauge is normally used from a surface
plate or table. It is designed for accurate marking or
checking heights.

Vernier height gauge fig. 5.28

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 9

Information Sheet 5.1.1: Layout tools
Parts of a Vernier Height gauges.

Parts of a Vernier height gauge
fig. 5.29

Base

This is the datum which measurements and settings are made. The underside of the base is
hardened, ground and lapped.

Beam
This is similar to the beam scale of a vernier caliper is attached to the base.

Vernier slide

This unit slides on the beam and carries the vernier plate, locking screws, and fine setting
device and scriber. Some vernier height gauges are provided with a rack and a pinion
arrangement of moving the slide along the beam.

They are also provided with straight and offset scribers.

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 10

Information Sheet 5.1.1: Layout tools

Zero setting of the vernier height gauge

The offset scriber permits zero setting of the instrument from the datum surface. While using a
straight scriber, the zero setting of the instrument is at a level above the datum surface. In this
case the zero setting is to be checked using the precision round block, supplied along the
instrument.
Vernier height gauge with which can measure from the datum surface without the special
offset scribers are also available.

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 11

Operation Sheet 5.2.1: Lay outing

Learning outcomes:
1. Work pieces are filed to within tolerance specified in the drawing.
2. Bench work operations are performed applying knowledge on safety procedures and using

personal protective devices.
Learning Activity:
5.1 Identify the different layout tools.
5.2 Describe the application of the different types of layout tools.
5.3 Identify the different lay-outing techniques.
5.4 Sequences lay outing techniques.

Lay outing
Laying-out is the planning of the work on the surface of the material to be made into the
finished part. It is the scribing of lines, which indicates cuts to be made the centerlines of holes
to be drilled and other details that guide the workman in completing the job.

Steps in making a layout

 First study the drawing carefully.

 Then cut the work to required size and remove all sharp edges.

 A base or reference surface is selected from which to begin making the measurements.
On a flat layout, this is commonly the smoothest, straightest edge on the piece. On
some layouts, base lines instead of surfaces are used as reference points for
measurements.

 The base or reference surface must be kept clean and free from scratches, nicks, and
burrs that would impact the accuracy of the reference surface and the layout work being
done on it.

 The work piece is then coated with a "bluing" or purple layout dye (figure 5.1). This
makes the scribed lines highly visible, thus contributing to the accuracy of the work.
After the part has been machined, the layout dye can be washed off with lacquer thinner
or polished off with abrasive cloth.

Code No. Perform Bench work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 1

Operation Sheet 5.2.1: Lay outing

Preparing work for lay outing fig. 5.1

 Locate and scribe a reference line or base line. Make all your measurements from this
line. If the material has one true edge, it can be used in place of reference line.

 Locate the center points of all circles and arcs.

 Use the prick punch, to mark the point where the centerline intersects. The sharp point
(30 to 60) of this punch make it’s easy to locate this position. After the prick punch
mark has been checked and found on the center, it is enlarged with the center punch.

 Using the divider or trammel, scribe in all arcs and circles.

 If angular lines are necessary, use the proper protractor type tool, or locate the correct
points by measuring, and connect them by using a rule or a straight edge.

 Scribe in all other internal openings.

 Use only clean sharp lines. Any double or sloppy line should be remove by cleaning, or
applying another coat of dye and the line re-scribed.

Code No. Perform Bench work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 2

Operation Sheet 5.2.1: Lay outing
Example

Let’s look on this example; the work piece below is the part that we will make a layout on a
metal plate,

fig. 5.2

To layout we must:

 Fist Locate and scribe base lines (figure 5.3).

fig. 5.3

 Second, locate all circle and arc centerlines
(figure 5.4).

fig. 5.4

 Then, Scribe in all circles and arcs (figure 5.5).

fig. 5.5

Code No. Perform Bench work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 3

Operation Sheet 5.2.1: Lay outing fig. 5.6
 Locate and scribe in angular lines (figure 5.3). fig. 5.7

 Finally, Complete all other object lines (figure
5.3).

Code No. Perform Bench work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 4

Worksheet 5.2.1: Layout tools and lay outing

Learning outcomes:
1. Work pieces are filed to within tolerance specified in the drawing.
2. Bench work operations are performed applying knowledge on safety procedures and using

personal protective devices.
Learning Activity:
5.1 Identify the different layout tools.
5.2 Describe the application of the different types of layout tools.
5.3 Identify the different lay-outing techniques.
5.4 Sequences lay outing techniques.

Material needed
6 x 6 inch carton, pencil, ruler, marker, compass, masking tape.

Instructions

Given the necessary material and the layout below, mark your work with the necessary lines
needed to fabricate the work in the bench area. Units are in English.

Code No. Work Holding Devices Date: Developed Date: Revised Page #
ALT723307
April 2010 1

Information Sheet 6.1.1: Drills and Drilling

Learning outcomes:
1. Bench work operations are performed applying knowledge on safety procedures and

using personal protective devices.
2. Hole is drilled, reamed, spot-faced and lapped to drawing specification.
3. Drilling, reaming or lapping holes are performed according to recommended sequence.
4. Operations are performed applying knowledge on safety procedures and using personal

protective devices

Learning Activity:
6.1 Identify the different types of drilling machine.
6.2 Describe the application of the different types of drilling machine.
6.3 Describe the application of the different types of drill bit.
6.4 Identify the different types of work holding device.
6.5 Lay out work to be drilled according to requirements.
6.6 Set up work piece.
6.7 Sequences drilling operation.

Drills and Drilling Process

Drilling is the operation of producing a circular hole by
removing solid metal. The cutting tool used is the drill.

Drilling has different process involving reaming,
boring, counter boring, and countersinking, spot
facing, and tapping. These processes are made in
different types of drilling machines.

Standard drilling machine commonly found in the shops:

 Portable drilling machine Portable drill fig. 6.1

This tool is a portable device for drilling holes on
metal and alike. A drill chuck hold the drill, the
speed of the spindle is controlled by a switch
which is triggered by hand. These drills are used
for light work only.

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 1

Information Sheet 6.1.1: Drills and Drilling fig. 6.2
Floor type drilling machine fig. 6.3
 Bench drilling machine
The bench-drilling machine is the most common
drilling machine found in machine shops (figure
6.2). These types of drilling machine are use for
light duty works.

This machine is capable of drilling hole up to 12.5-
mm diameter. The drills are fitted in the chuck or
directly in the tapered hole of the machine spindle.

 Floor type drilling machine

This machine, sometimes-called upright drill press,
has six or more spindle speeds and three or more
automatic feeds (figure 6.3). They have circular or
rectangular columns, the head, which carries the
sleeve, spindle and feed gears, is in many models
bolted on the frame and, to accommodate different
heights of work. The worktables are vertically
adjustable and may be swing entirely out of the
way of the work seated on the base.

 Radial Drilling Machine
This are drilling machine having the drill head
mounted on or in an arm attached to a vertical
column (figure 3.4). The drill head may be
mounted in a fixed position in the arm or attached
by a geared mechanism to adjust the length of the
swing. This drilling machine holds larger drills than
the pedestal type, thus, are used for heavy duty
works.

Radial drill fig. 6.4

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 2

Information Sheet 6.1.1: Drills and Drilling
Parts of a Drilling Machine

All drilling machines have the following basic construction characteristics: a spindle, sleeve or
quill, column, head, worktable, and base.

 Head

The head of the drill press is composed of the
sleeve, spindle, electric motor, and feed
mechanism. The head is bolted to the column.

 Driving motor
Drives all of the mechanism of the machine.

 Head clamping Screws
Clamps the head to the column

 Speed change gear case fig. 6.4
Houses the gears/ Belts that control the speed of
the spindle.

 Speed change lever
Controls the speed change gears.

 Column

The column of most drill presses is circular and
built rugged and solid. The column supports the
head and the sleeve or quill assembly.

 Spindle

The spindle holds the drill or cutting tools and
revolves in a fixed position in a sleeve. In most
drilling machines, the spindle is vertical and the
work is supported on a horizontal table.

fig. 6.5

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 3

Information Sheet 6.1.1: Drills and Drilling

 Work Table

The worktable is supported on an arm mounted to
the column. The worktable can be adjusted
vertically to accommodate different heights of
work, or it may be swung completely out of the
way. It may be tilted up to 90° in either direction, to
allow for long pieces to be end or angled drilled.
The standard drill press may have either a
rectangular or a round worktable.

 Base Portable drill fig. 6.6

The base of the drilling machine supports the
entire machine and when bolted to the floor,
provides for vibration-free operation and best
machining accuracy. The top of the base is similar
to a worktable and may be equipped with T-slots
for mounting work too large for the table.

 Sleeve fig. 6.7

The sleeve or quill assembly does not revolve but
may slide in its bearing in a direction parallel to its
axis. When the sleeve carrying the spindle with a
cutting tool is lowered, the cutting tool is fed into
the work; and when it is moved upward, the cutting
tool is withdrawn from the work.

 Feed depth Dial/ Depth gauge rod

Determine the depth of the hole when feeding the
drill in to it.

 Feed change lever
Control the setting of the automatic feed.

 Feed clutch fig. 6.8

Permits the operator to engage or disengage the
feed without removing his hand

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 4

Information Sheet 6.1.1: Drills and Drilling

Before accurate work can be produce it is necessary fig. 6.9
to set up the work correctly. This requires the use of fig. 6.10
certain attachments and accessories such as a drill
vise, angle plates, v-blocks, a drill jig or fastener such fig. 6.11
as clamps and T-bolts, washers and nuts.

Work attachment and accessories

 The Drill Vise
The Drill press vise is by far the most common
type of work holding device used on the drill press
(figure 6.10). Modern drill press vises are capable
of holding round stock, flat stock, or any other
small parallel-sided parts. Most drill press vises
come equipped with V shaped slots for holding
round stock and stepped jaws for holding parts up
off the base of the vice. This will avoid contact
between the drill and the vise.

 Angle vise
Is used when an angular hole needs to be drilled
in a part (figure 6.11). Angle vises have an angular
adjustment, which allows the operator to tilt the
vise.
Another method of drilling angular holes, on
certain types of drill press, is by tilting the drill
press table.

 Swivel vise
Another work holding devise is the Swivel vise
(figure 6.12). This vise has a base graduated in
degrees and a body that can be turned on the
base and fastened at any angle.

fig. 6.12

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 5

Information Sheet 6.1.1: Drills and Drilling fig. 6.13
fig. 6.14
 Angle Plates
Angle plates are used when drilling odd shaped
parts that need to be drilled at 90 degrees to the
axis of the table. An angle plate is an L shaped
piece of Cast Iron or Steel that has tapped holes
or slots to facilitate the clamping of the work piece
(figure 6.13).

 Parallels
Parallels are hardened, accurately ground steel
bars of various thickness, widths and lengths
which are used to raise the work piece and seat it
square and parallel with the base of a vise or table
of the drilling machine.

 V-Blocks with clamps
This are used to hold cylindrical work securely
during the laying out of measurements or for
machine operations (figure 6.14).

 Clamps

Plain slot clamp- is provided with bolt hole fig. 6.15
somewhat nearer the front or work end, the front
end is usually beveled (figure 6.15).

Adjustable step clamp- has an adjusting screw,
which permits the leveling of the strap from the
work to the step block (figure 6.16).

Goose neck clamp- permits clamping of large fig. 6.16
thicknesses without the use of long clamping bolts.
It reduces the height of the step block required
(figure 6.17).

fig. 6.17

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 6

Information Sheet 6.1.1: Drills and Drilling fig. 6.18
fig. 6.19
Finger single end clamp- is made to use in a hole
in a job using ordinary block in clamping (figure
6.18).

Finger double end clamp- is used mostly in
production work, each finger being inserted in a
hole to clamp the work

U- clamp- may be removed from the bolt without
removing the nut. It is very convenient for purpose
of adjustment (figure 6.19).

 Step Block
A step block is a tool which is used to assist with
clamping items to a table. The step block is
adjustable so that the clamps can be placed at the
right height. It is made of hardened steel blocks
with step that provide a firm grip when holding and
supporting step clamps.

fig. 6.20

 Drill Jigs

A Drill jig is a work holding tool that locates the work piece in proper position and holds it
securely. The drill and other cutting tools are guided by hardened steel bushings so that the
holes in all of the parts so drilled are in the same direction. Drill jigs are production tools
used in mass production of parts.

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 7

Information Sheet 6.1.1: Drills and Drilling

Types of Drill Bits
 Straight shank drill- this drills are used with a drill chuck mounted in the drilling machine.

Metric drill sizes ranging from 1 mm to 25 mm usually has a straight shank body.

 Tapered shank drills- this drill has a tapered shank that can be mounted directly in the
drilling machine spindle or with the use of a drill socket or sleeve. Most larger size drill from
25 mm up have a tapered shank.

fig. 6.21

 Straight fluted drills- are used for drilling brass, copper, and other soft metals, a drilling
with rake (twist drill) has a temporary tendency to “dig” or grab.

 Oil tube drills- this drills has special holes that are inside the drill body that enables oil or
coolant to pass on the drill while drilling.

 Center Drills- is used to produce accurate and Center drills fig. 6.22
true position for starting follow up drills, and
obtaining perfect alignment. Their short flute and
overall lengths and no body clearance permit
chucking close to the point so that they will
produce a true start or center.

Center drills are made with a constant web in
order that subsequent re-sharpening of the drills
requires no web thinning. In addition, they are
useful in spotting holes for tap drilling and will
reduce tap breakage on tapped holes

fig. 6.23

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 8

Information Sheet 6.1.1: Drills and Drilling fig. 6.24
fig. 6.25
Tools used to hold drills while drilling in a drilling machine

 Drill chucks
A chuck is a gripping device with two or more
adjustable jaws set radially (figure 6.24). A drill
chuck is made especially for holding straight
shank drills or cutting tool in the spindle of the
machine and itself provided with a taper shank,
which fits the taper hole in the spindle. They are
made in various sizes and a series of three or four
chucks will hold drills from the smallest size up to
1” in diameter.

 Sockets and Sleeves
A drill machine spindle is provided with a standard
taper hole of a size in proportion to the size of the
machine. Several types of drill, for example, have
shanks, which will fit the spindle others are too
small and, to step the sizes sockets or sleeve are
used.

 Drill drifts
A tapered key or drill drift is used to remove the
taper shank from the taper hole (figure 6.26). Do
not use anything but a drift for this purpose and
use the rounded edge against the rounded edge of
the hole.
The taper shanks of drills, reamers, counterbore,
etc. and also of the sockets and sleeves have the
end flattened to form a tang that fits in a suitable
slot at the end of the taper hole in the shank is
held.

fig. 6.27

fig. 6.26

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 9

Operation Sheet 6.2.1: Drilling Operations

Learning outcomes:
1. Bench work operations are performed applying knowledge on safety procedures and using

personal protective devices.
2. Hole is drilled, reamed, spot-faced and lapped to drawing specification.
3. Drilling, reaming or lapping holes are performed according to recommended sequence.
4. Operations are performed applying knowledge on safety procedures and using personal

protective devices.

Learning Activity:
6.1 Identify the different types of drilling machine.
6.2 Describe the application of the different types of drilling machine.
6.3 Describe the application of the different types of drill bit.
6.4 Identify the different types of work holding device.
6.5 Lay out work to be drilled according to requirements.
6.6 Set up work piece.
6.7 Sequences drilling operation.

Drilling machine safety
Drilling machines are one of the most dangerous hand operated pieces of equipment in the
shop area. Following safety procedures during drilling operations will help eliminate accidents,
loss of time, and materials. Listed below are safety procedures common to most types of
drilling machines found in the machine shop.

 Do not support the work pieces by hand. Use a holding device to prevent the work piece
from being torn from the operator's hand.

 Never make any adjustments while the machine is operating.
 Never clean away chips with your hand. Use a brush.
 Keep all loose clothing away from turning tools.
 Make sure that the cutting tools are running straight before starting the operation.
 Never place tools or equipment on the drilling tables.
 Keep all guards in place while operating.
 Ease up on the feed as the drill breaks through the work to avoid damaged tools or work

pieces.
 Remove all chuck keys and wrenches before operating.
 Always wear eye protection while operating any drilling machines.

Code No. Perform Bench work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 1

Operation Sheet 6.2.1: Drilling Operations

 Mounting work pieces
Before attempting to use a drilling machine, some provision must be made for holding the
work piece rigidly and securely in place. The work piece should always be firmly fastened
to the table or base to produce holes that are located accurately. Use work holding devices
to hold the work piece. The two best methods to mount work pieces are explained below.

Vise Mounting Vise mounting fig. 6.1

Most hand-feed drilling machines have no means of
clamping or bolting work pieces to the table or base.
The work piece must be secured tightly in a machine
table vise and swung around so that the tail of the
vise contacts the column of the drill press. The hole
must be centered by hand so that the center drill point
is directly over the center punched mark. Other larger
drilling machines have slotted tables and bases so
that the work and work holding devices can be bolted
or clamped firmly. All work should be securely
clamped or set against a stop for all drilling to avoid
letting the drill grab and damage the work piece or
injure the machine operator.

Table or Base Mounting Table mounting with clamps and
step block fig. 6.2
When a work piece is table or base mounted, the
strap clamps must be as parallel to the table or base
as possible. All bolts and strap clamps should be as
short as possible for rigidity and to provide for drilling
clearance.

Parallel bars should be set close together to keep
from bending the work. Washers and nuts should be
in excellent condition. The slots and ways of the table,
base, or vise must be free of all dirt and chips. All
work holding devices should be free of burrs and
wiped clean of oil and grease. Work holding devices
should be the right size for the job. Devices that are
too big or too small for the job are dangerous and
must be avoided.

Table mounting with
angle plate fig. 6.3

Code No. Perform Bench work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 2

Operation Sheet 6.2.1: Drilling Operations
Cutting Speed and R.P.M
For a drill to give a satisfactory performance, it must operate at the correct cutting speed and
feed.
Cutting speed is the speed at which the cutting edge passes over the material while cutting,
and is expressed in meters per minute. Cutting speed is also sometimes stated as surface
speed or peripheral speed.
The selection of the recommended cutting speed for drilling depends on the material to be
drilled, and the tool material.
Tool manufacturers usually provide a table of cutting speeds required for different materials is
given in the table.
Based on the cutting speed recommended, the r.p.m (revolution per minute) at which the drill
is to be driven is determined.

Cutting speed calculation

Table for Cutting Speed Calculations

Table of cutting speed. 6.4

Code No. Perform Bench work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 3

Operation Sheet 6.2.1: Drilling Operations

Example
Calculate the r.p.m for a high-speed steel drill 24-mm to cut mild steel.
The cutting speed for mild steel is taken as 30m/ min from the table.

NOTE:

It is always preferable to set the spindle speed to the nearest available lower range. The
cutting speed being the same, larger diameter drills will have lesser r.p.m and smaller diameter
drills will have higher r.p.m. The recommended cutting speeds are achieved only by actual
experiment.

Feed in Drilling

Feed, in machinist term, is the distance a tool advances in the work being cut or being drilled
advances in to the in one complete rotation. Feed is expressed in hundredths of a millimeter.
example – 0.040 mm (figure 6.5).

The rate of feed is dependent upon a number of factors:
 The finish required
 Type of drill (drill material)
 Material to be drilled

Factors like the rigidity of the machine, holding of the Table of drill feed fig. 6.5
work piece and the drill, will also have to be
considered while determining the feed rate. If these
are not to the required standard, the feed rate will
have to be decreased.

It is not possible to suggest a particular feed rate taking all the factors account. The table will
give you the feed rate based on the average feed values suggested by the different
manufacturers of drills.

To course a feed may result in damage to the cutting edges or break the drill.

To slow the rate of feed will not bring improvement in the finish but may cause excessive wear
of the tool point, and lead to chattering of the drill.

For optimum results in the feed rate while drilling, it is necessary to ensure the drill cutting
edges are sharp. Use the correct type of cutting fluid.

Code No. Perform Bench work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 4

Operation Sheet 6.2.1: Drilling Operations

Drilling Operations

Drilling
Drilling is an operation of producing a circular hole by removing metal with the use of a cutting
tool called a drill or drill bit.
The two most common drilling operations in machine shop maintenance and repair work are:

 Clear hole drilling
Drilling a hole of a specific diameter completely through a work piece.

 Blind hole drilling
Drilling a hole of a specific diameter to a given depth in a work piece.

Before performing either of these operations, however, the work piece must first be marked to
indicate where the hole should be drilled.

Locating the Hole
There are several ways to mark the location of a hole on a work piece before drilling. The
method you choose will usually depend on the degree of accuracy required.

 Marking
For most maintenance and repair drilling, marking the location of a hole is quiet simple: the
work piece is measured to determine where the hole should be drilled, and the spot is
marked with a scribe or marking pen. The piece is then set up and drilled.

 Center Punching
When more accuracy is required, the work piece is marked, then a center punch is used to
make an indention in the work piece to serve as a guide for the drill bit point.

Code No. Perform Bench work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 5

Operation Sheet 6.2.1: Drilling Operations

 Center Drilling
An even greater degree of drilling accuracy can be obtained by center drilling the work
piece. A special bit called a center drill is used to drill a shallow center hole. The hole made
by the center drill is a much more accurate guide for drilling than the center punch
indention.

Pilot Hole Drilling

In many insistences, particularly when drilling large
diameter holes, a pilot hole is drilled to serve as
guide. To prevent uneven drilling and damage to the
drill bit, pilot holes should be about one-quarter the
diameter of the bit used to drill the finished hole.

Clear Hole Drilling

Pilot hoe drilling fig. 6.6

Most of the work piece involved in clear drilling a hole in a work piece is performed before the
actual drilling takes place.

 First, the proper size and type of drill bit must be selected and mounted. Then, the correct
drill speed (and feed rate if you are using an automatic feed) must be calculated and set;
and finally, the work piece must be properly marked and set up, either on the worktable or
in the vise.

 Once you begin drilling the work piece, make sure you back the drill out of the hole
occasionally. For most materials, backing out about once every eight of an inch of feed is
sufficient,. This allows the bit to throw off chips and helps keep the flutes from clogging and
causing the bit to jam in the hole

 Often, as the drill bit breaks through the work piece, the edges of the exit hole can splinter,
making the surface around the hole uneven. This can usually be prevented by fastening a
scrap piece of stock securely beneath the work piece during set up.

 After the hole is drilled, a special bit called a countersink should be used to de-burr the
edges of the entry and exit holes. De-burring smooth out the surface of the holes to prevent
injury to anyone who handles the piece, and assures a close fit for any mating surfaces.
The bit is mounted in the drill press and fed into each hole just enough to remove any metal
burrs or sharp edges. The typical de-burring depth is one-sixteenth of an inch.

Code No. Perform Bench work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 6

Operation Sheet 6.2.1: Drilling Operations

Blind Hole Drilling

The preparations for blind hole drilling are essentially the same as for clear hole drilling. Before
the operation begins, the proper drill bit is selected and mounted; the proper speed is
calculated and set; and work piece is marked and setup. However, when blind hole drilling, you
must also adjust the depth stop to keep from drilling too deeply. Depth stop adjustments differ
from drill press to drill press, so make sure you know how to set the stop on the machine you
are using before you attempt to drill a blind hole.

To drill a blind hole using a depth stop:

 Set the depth stop to stop the bit short of the desired depth and drill a preliminary hole.
 Measure the hole and set the additional depth on the depth stop.
 Drill the hole to the final depth.

For ample, to drill a half-inch blind hole, mount the work piece on the table, lower the ex quill
so the drill bit contacts the work piece, then set the depth stop to drill less than half an inch into
the work piece.

Start the drill, and feed the bit into the work piece. Then, measure the depth of the hole from
the edge of the work piece to the point where the margin of the drill stopped. If the preliminary
hole is three-eighths of an inch deep, the depth stop should be set to allow the bit to feed an
additional eight of an inch. Most drill presses can be used to drill blind holes accurate to within
one-sixteenth of an inch. Many are capable of much greater accuracy when used carefully by a
skilled operator.

Measuring the Depth of a Blind Hole

The depth stop is also useful when performing multiple operations. For example, when drilling
several clear holes, the stop should be set to drill through the work piece but not into the table
or vise. When de-burring several clear or blind holes, set the stop to drill just a fraction of an
inch into the work piece.

If your drill press does not have a depth stop, you can measure and mark the drill bit to
indicate when you have drilled to the proper depth. The measurement should start at the
margin of the drill, not from the point. A brightly colored marking pencil or a piece of tape can
be used to show the stopping point on the drill bit.

Code No. Perform Bench work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 7

Operation Sheet 6.2.1: Drilling Operations

Once you begin drilling, remember to back the bit out of the hole once every eighth of an inch
of feed to keep the flutes from clogging.
When you finish the hole, use a countersink to de-burr the edge.

Countersinking Countersink hole fig. 6.7
Countersink fig. 6.8
Countersinking is used for the following purposes:
 To provide a recess for the head of a
countersink screw, so that it is flush with the
surface after fixing.
 To de-burr a hole after drilling.
 To accommodate countersink rivet heads.
 To chamfer the ends of hole for thread cutting
and other machining processes.

Counter sinks are available in different angles for
different uses. Here are some of them:

 75 Counter sink for riveting
 80 Counter sink for self tapping screws
 90 Countersink for head screws and for

deburring
 120 Chamfering end s of holes to be threaded

or other machine processes.

Counter boring
Counter boring is an operation of enlarging at the end
of a hole cylindrically, as for recess for a fillister- head
screw with the use of a counter bore.

The tool used for Counter boring is called counter
bore. Counter bores have two or more cutting edges.

Counter bore fig. 6.9

Code No. Perform Bench work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 8

Operation Sheet 6.2.1: Drilling Operations

At the cutting end, a pilot is provided to guide the tool Counter bore with solid pilot
concentric to the previously drilled hole. The pilot also fig. 6.10
helps to avoid chattering while Counter boring.

Counter bores are available with solid pilots or with
interchangeable pilots. The interchangeable pilots
provide flexibility of counter boring on different
diameters of hole.

Reaming
Reaming is an operation of sizing and finishing a hole
by means of a cutting tool having several cutting
edges. This tool is called a reamer. Reaming serves
to make the hole smoother, straighter, and more
accurate.

Code No. Perform Bench work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 9

Worksheet 6.2.1: Drills and Drilling

Learning outcomes:
1. Bench work operations are performed applying knowledge on safety procedures and using

personal protective devices.
2. Hole is drilled, reamed, spot-faced and lapped to drawing specification.
3. Drilling, reaming or lapping holes are performed according to recommended sequence.
4. Operations are performed applying knowledge on safety procedures and using personal

protective devices.

Learning Activity:
6.1 Identify the different types of drilling machine.
6.2 Describe the application of the different types of drilling machine.
6.3 Describe the application of the different types of drill bit.
6.4 Identify the different types of work holding device.
6.5 Lay out work to be drilled according to requirements.
6.6 Set up work piece.
6.7 Sequences drilling operation.

Instructions

Write on the space the letter of the correct answer.

1. ____Other name for the floor type-drilling machine.

a. Radial drilling machine
b. Drill press
c. Upright Drill press
d. Floor Drill

2. _____The speed at which the cutting edge passes over the material while
cutting and is expressed in meters per minute of feet per minute.

a. Velocity
b. R.P.M
c. Feed
d. Cutting Speed

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
ALT723307
April 2010 1

Worksheet 6.2.1: Drills and Drilling

3. ____ A gripping device with two or more adjustable jaws set radially and is for
holding straight shank drills or cutting tool in the spindle of the machine and itself
provided with a taper shank, which fits the taper hole in the spindle of a drilling
machine.

a. Drill Drift
b. Drill chuck
c. Drill Socket
d. Drill Sleeve

4. ____This vise has a base graduated in degrees and a body that can be turned
on the base and fastened at any angle.

a. Angle Vise
b. Swivel Vise
c. Vise Grip
d. Drill press Vise

5. ____This are used to hold cylindrical work securely during the laying out of
measurements or for machine operations.

a. Angle Plate
b. Swivel Vise
c. V-Blocks
d. Angle Vise

6. ____This tool is a portable device for drilling holes on metal and alike.
a. Portable Drill
b. Drill Press
c. Bench Drill
d. Radial Drilling Machine

7. ____This drills have special holes that are inside the drill body, which enables oil
or coolant to pass on the drill while drilling.
a. Oil-tube drill
b. Center Drill
c. Three fluted drill
d. Straight Fluted Drill

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
ALT723307
April 2010 2

Worksheet 6.2.1: Drills and Drilling

8. ____Why it is necessary to use a center drill before using the necessary drill?
a. To provide a kerf.
b. To provide an initial hole as a guide for the drill.
c. To retain sharpness of the drill.
d. To allow the drill to cut easier from the work.

9. ____How can a dull drill cause an accident?
a. A dull drill will not cut, and pressure applied on the drill causes it to break and
the flying pieces can cause serious injury.
b. A dull drill will not cut and produce friction on the work causes it to be heated
and may burn your hand when accidentally touched.
c. A dull drill will not cut causing the drill to be overheated.
d. All of the above.

10. ____An operation of enlarging at the end of a hole cylindrically, as for recess for a
fillister- head screw with the use of a counter bore.

a. Reaming
b. Drilling
c. Boring
d. Counter boring

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
ALT723307
April 2010 3

Information Sheet 7.1.1: Threads and Threading

Learning outcomes:
1. Thread is cut to fit gage or mating screw, within tolerance given in the blueprint
2. Thread is cut in accordance with the recommended tapping sequence
3. Thread cutting operations are performed applying knowledge on safety procedures

and using personal protective devices.

Learning Activity:
7.1 Identify the different types of threads.
7.2 Describe the application of the different types of threads.
7.3 Identify the parts of a screw threads
7.4 Determine the TDS for a specific pitch of thread.
7.5 Identify the different types of taps and dies.
7.6 Determine the types of taps and dies to be used.
7.7 Describe procedure in cutting threads using taps and dies

The Screw Thread
A screw thread is a ridge of uniform section formed helically on the surface of a cylindrical
body. An external screw thread is formed on the outer surface of a cylindrical part.

Screw threads are used:
 As fastener to hold together and dismantle components when needed.
 To transmit motion on machines from one unit to another.
 To make accurate measurements.
 To apply pressure.
 To make adjustment.

Classification of Screw Threads

1. External and internal threads External thread fig. 7.1

An external thread is a thread on the outside of a part
(figure 7.1). An example is the thread on a machine
bolt. An internal thread is a thread on the inside of a
part (figure 7.2). An example is the thread in a nut.

Internal thread
fig. 7.2

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 1

Information Sheet 7.1.1: Threads and Threading fig. 7.4
fig. 7.5
2. Hand of a thread
Sharp V threads fig. 7.6
The direction in which the thread is turned to American National fig. 7.7
advance. A right hand thread is one that, when Acme threads fig. 7.8
assembled with a fixed matting thread, is turned in
a clockwise direction (figure 7.5). A left-hand Square thread fig. 7.9
thread is one that, when assembled with a fixed
mating thread is turned in a counter clockwise
direction (figure 7.4).

3. Types of a Screw Thread

 Sharp V Thread

The Sharp V thread form is one of what is known
as the locking threads (figure 7.6). Matching
threaded parts cut to this form fit closer and will
seal better than any other thread form produced,
because of wedging action of the sharp top and
bottom.

 American National Thread
The top and bottom of this thread are flat (figure
7.7). This thread has more strength and locking
characteristics of the sharp V thread are largely
retained, the thread withstands more abuse
without damage on the threads.

 American National Acme Thread
These threads are classified as a power-
transmission type of thread (figure 7.8). It has 29º
included angle at which its sides slope reduces the
amount of friction when matching parts are
unloaded.

 Square thread
All surfaces of square threads are square with
each other, and the sides are perpendicular to the
center of the axis of the work (figure 7.9). The
depth, crest, and the root are equal. Because of
this characteristic, square threads are used for
maximum transmission power.

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 2

Information Sheet 7.1.1: Threads and Threading

 Knuckle Threads Knuckle thread fig. 7.10

The knuckle thread is a modified form of a square
thread. It has a rounded crest and root that form
like a semicircle (figure 7.10). An example of this
thread is the one used for railway wagon
couplings.

 Buttress Thread
Buttress thread provides a form of thread used
when very high pressure is required to be taken in
one direction parallel to the axis of the thread
(figure 7.11).

Buttress thread fig. 7.11

 The Metric threads
This thread has sides set at a 60º included angle, the same as for V sharp thread and the
American National (figure 7.12). Its depth is greater than the American National and the
bottom is rounded to a radius of approximately 1/16 of the pitch.

Metric thread fig. 7.12

fig. 7.13

Metric threads are designated by the letter M followed by the nominal major diameter of the
thread and the pitch in millimeters (figure 7.13).

For example M10 x 1.0 indicates that the major diameter of the thread is 10mm and the
pitch is 1.0mm. The absence of a pitch value indicates that a coarse thread is specified. For
example stating that a thread is M10 indicates a coarse thread series is specified of
diameter 10mm (giving the thread a pitch of 1.5mm).

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 3

Information Sheet 7.1.1: Threads and Threading
Parts of Screw Threads

fig. 7.15

fig. 7.14

 Major Diameter

Commonly known as the outside diameter. On a straight screw thread, the major diameter
is the largest diameter of the thread on the screw or nut.

 Minor Diameter

Commonly known as the root diameter. On a straight screw thread, the minor diameter is
the smallest diameter of the thread on the screw or nut.

 Lead fig. 7.16

The distance a screw thread advances in one revolution. The lead and the pitch of a single
lead thread are the same. On double lead threads, the lead is twice the pitch. A double lead
thread has two start points.

 Pitch
The distance from a given point on one thread to a corresponding point on the next thread.

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 4

Information Sheet 7.1.1: Threads and Threading

 Angle of Thread
The angle of the thread is the included angle between the sides of the thread. For example
the thread angle for Unified Screw Thread forms is 60 degrees.

 Flank
The surface connecting the crest and root.

 Crest
The top surface of the thread bounded by the flanks.

 Root
The bottom surface joining the flanks of adjacent threads. The root diameter is same as the
minor diameter.

 Depth
The perpendicular distance between the root and crest of the thread.

 Clearance
A space left between the mating external and internal threads to facilitate easy rotation of
threaded parts.

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 5

Information Sheet 7.1.1: Threads and Threading fig. 7.17
Set of hand taps fig. 7.18
Cutting Internal Threads with a Tap

Taps
A tap is a tool for cutting internal threads. It has
threads like a bolt with two, three, or four flutes
(grooves) cut across the threads. The edges of the
thread formed by the flutes are the cutting edges. The
shank end of the tap is square so that it can be turned
with a wrench.

Taps are made from carbon steel or high speed steels
and are hardened and tempered. A set of hand tap
includes a taper tap, a plug tap, and a bottoming tap
these are what we called set of hand tap.

Sets of Hand Tap (figure 7.18)

 Taper Tap
The taper tap has about six threads tapered at the
end so that it will start easily. The taper also
makes it easier to keep the tap straight as the cut
is begun. The threads are cut gradually as the tap
is turned into the hole.

 Plug Tap
The plug tap has three or four threads tapered at
the end and is used as a starting tap on easily cut
metals. A plug tap is used if the hole to be
threaded is blind.

 Bottoming Tap
When it is necessary to for the threads at the
bottom of a hole to be fully cut, then a bottoming
tap is used. It has full threads except for the first
thread and is used to cut full thread as close as
possible to the bottom of a hole.

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 6

Information Sheet 7.1.1: Threads and Threading

Tap styles
Taps are made in many styles to suit various hand and machine-tapping operations.
 Hand taps

This are straight fluted tap, that has a three or four flutes, and have a cutting edge parallel
to the centerline of the tap.
 Gun taps
Are straight fluted, with two, three or four flutes depending on the size of the tap
The cutting edges are ground at an angle to the centerline of the tap. The angular cutting
edge causes the chips to shoot ahead of the tap. This tap is designed for efficient chip
removal.
 Helical fluted taps
This taps are commonly known as spiral fluted taps are designed to lift the chips out of the
hole being tapped. For this reason they are well suited for tapping end holes.

Tap Wrench

A tap wrench is a hand tool for gripping and holding a tap securely. For the smaller sizes of
taps, a” T” handle type is used (figure 7.20). For large sizes of taps, the adjustable tap wrench
is preferred (figure 7.19).

fig. 7.20

fig. 7.19

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 7

Information Sheet 7.1.1: Threads and Threading

The Tap Drill Size
Before a tap is used for cutting internal threads, a hole is to be drilled. The diameter of the hole
should be such that it should have sufficient material in the hole for the tap to cut the thread.
To get the proper hole for tapping use the formula below:

Tap Drill Size (TDS) for different threads

Bolt Diameter Pitch TDS Bolt Diameter Pitch TDS
M2 19.5
M 2.2 0.4 1.6 M 22 2.5 21
M 2.5 24
M3 0.45 1.75 M 24 3 26.5
M 3.5 29.5
M4 0.45 2.05 M 27 3 32
M 4.5 35
M5 0.5 2.5 M 30 3.5 37.5
M6 40.5
M8 0.6 2.9 M 33 3.5 43
M 10 47
M 12 0.7 3.3 M 36 4 50.5
M 14 55
M 16 0.75 3.7 M 39 4 58
M 18 62
M 20 0.8 4.2 M 42 4.5

1 5 M 45 4.5

1.25 6.8 M 48 5

1.5 8.5 M 52 5

1.75 10.2 M 56 5.5

2 12 M 60 5.5

2 14 M64 6

2.5 15.5 M 68 6

2.5 17.5

fig. 7.21

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 8

Information Sheet 7.1.1: Threads and Threading

For English Calculations

The tap drill size for Unified American (National) forms of threads requiring 75 percent thread
depth may be calculated by subtracting the pitch from the major diameter. The pitch is equal to
1 divided by the number of threads per inch (figure 7.22).

fig. 7.22

Example:

Determine the drill size for a 3/8-16 UNC. The thread of approximately 75 percent threads
depth.

Given:
MD = 3/8”
TPI = 16

Required:
TDS =?

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 9

Information Sheet 7.1.1: Threads and Threading
Cutting External Threads with Dies

Threading Dies fig. 7.23

The main purpose of the diestocks is to produce
external threads by the manual process. Dies are
made from alloy steel, which are hardened, tempered
and accurately ground to the thread profile. Generally
they are designed with flutes for removing the cut
chips. In order to allow easy starting, the first few
threads are ground to chamfer and the rest of the
threads are allowed without chamfers.

Here are some types of threading dies

 Solid die or die nut Split button die fig. 7.24

This is mainly for cutting rough threads in one pass. They do not have facility for adjusting
the depth of the threads.

 Split button dies

The split button dies are largely used for cutting external threads (figure 7.24). It is difficult
to produce an accurate thread in one pass by using these dies. As the split of this die is
equipped with adjustment, varying the thread diameter and using more than one cut pass
may cut accurate threads.

 Adjustable dies

The construction of these dies is similar to that of
the button dies but they are designed with more
adjustment of the depth. These dies are used with
one special type of diestock.

Diestock fig. 7.25

If a tap has a tap wrench, a threading die has a
diestock that holds the die and provides leverage for
turning the die on the work to cut threads (figure
7.25).

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 10

Operation Sheet 7.2.1: Thread Cutting

Learning outcomes:
1. Thread is cut to fit gage or mating screw, within tolerance given in the blueprint
2. Thread is cut in accordance with the recommended tapping sequence
3. Thread cutting operations are performed applying knowledge on safety procedures and

using personal protective devices.

Learning Activity:
7.1 Identify the different types of threads.
7.2 Describe the application of the different types of threads.
7.3 Identify the parts of a screw threads
7.4 Determine the TDS for a specific pitch of thread.
7.5 Identify the different types of taps and dies.
7.6 Determine the types of taps and dies to be used.
7.7 Describe procedure in cutting threads using taps and dies

Thread Cutting

Hand Threading Safety

 If the tap, die or threaded piece is to be cleaned of chips with compressed air, protect
your eyes from flying chips by wearing goggles. Take care not to endanger persons
working in the area nears you.

 Chips produced by threading are sharp. Use a brush, or a piece of cloth to remove
them, not your hand.

 Newly cut external threads are also sharp. Again, use brush or a piece of cloth to clean
them.

 Wash your hands after using cutting fluids. Some cutting fluids causes skin rash. This
can develop into a serious skin disorder if the oils are left on the hands for extended
periods.

 Have cuts treated by a qualified person. Infections occur when injuries are not properly
treated.

 Be sure that the die is clamped firmly in the diestock. It may fall from the holder and
cause a painful foot injury.

 Broken taps have sharp edges and very dangerous. Handle them, as you would break
glass.

Code No. Perform Bench work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 1

Operation Sheet 7.2.1: Thread Cutting
Cutting internal Threads with the hand tap

Threads going all the away through the part are made with a Taper Tap. The long taper
permits easier and straighter starting. However, it cannot be used to thread to the bottom of a
blind hole, as the end of the tap will strike the bottom hole as the end of the hole before a full
thread can be cut.

The Plug Tap can be used in much the same manner as the taper tap if soft if soft material is
being threaded. It can be used to thread a blind hole, if the hole has been drilled deeper than
the required thread.

Threads that must be cut to the bottom of a blind hole are made with a Bottoming Tap.
Normally, the thread is started with a taper, cut further with a plug tap, and finished with a
bottoming tap.

When threading with taps follow these procedures:

 Determine the tap drill size either using the formula or the table.

 Drill the hole to the required tap drill size. An undersized hole will lead to breakage of
the tap.

 Chamfer the end of the hole for easy aligning and starting of the tap.

 Hold the work firmly and horizontally in the vice. The top surface of the job should be
slightly above the level of the vice jaws. This will help in using a try square without any
without any obstruction while aligning the tap.

 Fix the tap (taper tap) in the correct size tap wrench. Too small a wrench will need a
need a greater force to turn the tap. Very large and heavy wrenches will not give the
‘feel’ required to turn the tap as it cuts and may lead to breakage of the tap.

 Position the tap in the chamfered hole vertically by ensuring the wrench is in a
horizontal plane.

 Exert steady downward pressure and turn the tap wrench slowly in the clockwise
direction to start the thread; hold the tap wrench close to the center.

 Remove the wrench from the tap when you are sure of starting the thread without
disturbing the setting.

 Check and make sure that the tap is vertical by using a try square in two positions at
90 to each other.

 Make correction if necessary by exerting slightly more pressure on the opposite side of
the tap inclination.

 Check the tap alignment again. The tap alignment should be corrected within the first
few turns. If it is afterwards there is a chance of breaking of the tap.

Code No. Perform Bench work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 2

Operation Sheet 7.2.1: Thread Cutting

 Turn the wrench lightly by holding at the ends without exerting any downward pressure
after the tap is positioned vertically. The wrench pressure exerted by the hands should
be well balanced. Any extra pressure on one side will spoil the tap alignment and can
also cause breakage of the tap.

 Continue cutting the thread. Turn backwards frequently about a quarter turn to break the
chips.

 Stop and turn backwards when any obstruction to the movement is felt.
 Cut the thread until the hole is totally threaded.
 Finish and clean up using the intermediate and plug tap. The intermediate and plug tap

will not cut any thread if the first tap has entered the hole fully.
 Remove the chips from the work and clean the tap with a brush.

Care in tapping
 Use the correct size tap drill size. Secure this information from the tap drill chart or
consult your instructor.
 Use sharp tap and apply sufficient quantities of good cutting oil. Special tapping fluids
are available.
 Start taper tap square.
 Do not force the top to cut. Remove the chips as necessary.
 Avoid running the tap to the bottom of a blind hole while continuing to apply pressure.
Do not allow the hole to fill with chips and the tap.
 Remove burrs on tapped hole with a smooth file. Use a rag, not your fingers, to wipe
away excess cutting oil and chips.

Cutting External Threads with Dies

Here are some Helpful hints in making external thread using dies
 Select the correct size and circular rod as blank and chamfer ends.

 Material size = Thread size- 0.1%
 Get the Pitch of thread

 Grip the blank in the vice using a false jaw, projecting the blank above the vice jaws 5
mm more than the required length of thread.

 Fix the die in the diestock. The leading side of the die must be opposite to the step of
the diestock.

Code No. Perform Bench work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 3

Operation Sheet 7.2.1: Thread Cutting

 Open the die fully by tightening the center screw of the diestock.
 place the leading side of the die on the chamfer of the job
 Start the die, square to the bolt centerline.
 Turn in the clockwise direction to advance the die on the, with even pressure on both

ends of the diestock.
 Cut the thread slowly and reverse the die for a short distance in order to break the

chips.
 Clean the die frequently with a brush to prevent the thread from clogging and also from

spoiling the thread.
 Reverse and remove the die after the full height reached.
 Increase the depth of the cut gradually by loosening the center screw and tightening the

side screws.
 Too much depth of cut at one time will spoil the threads; it can also spoil the die.
 Check the fit of threads with a matching nut.
 Tighten the screws by hand and repeat the cutting until the standard nut matches with

the external, and without undue ‘play’ between the threads.

Measuring and Checking of Threads

Screw Pitch gauge Screw pitch gauge

Screw pitch gauge is used to determine the pitch of a
thread. It is also used to compare the shape of
threads.

Pitch gauges are available with a number of blades
assembled as a set. Each blade is meant for checking
a particular standard thread pitch. The blades are
made of thin spring steel sheets, and are hardened.

The thread size on each blade is cut for about 25 mm
to 30 mm. The pitch blade is stamped on each blade.
The standard and range of the pitches are marked on
the case.

NOTE:

For obtaining the accurate results while using the screw pitch gauge, the full length of the
blade should be placed on the threads.

Code No. Perform Bench work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 4

Worksheet 7.2.1: Threads and Threading

Learning outcomes:
1. Thread is cut to fit gage or mating screw, within tolerance given in the blueprint
2. Thread is cut in accordance with the recommended tapping sequence
3. Thread cutting operations are performed applying knowledge on safety procedures and

using personal protective devices.

Learning Activity:
7.1 Identify the different types of threads.
7.2 Describe the application of the different types of threads.
7.3 Identify the parts of a screw threads
7.4 Determine the TDS for a specific pitch of thread.
7.5 Identify the different types of taps and dies.
7.6 Determine the types of taps and dies to be used.
4.1 Describe procedure in cutting threads using taps and dies

Multiple choice

Write your answer on the space provided.

1. ______ These threads are on the outside of a part. An example of this is the thread on a
machine bolt.
a. Internal thread
b. External thread
c. Left hand thread
d. Right hand thread

2. ______ This thread classification when assembled with a fixed matting thread is turned in a
clockwise direction.
a. Internal thread
b. External thread
c. Left hand thread
d. Right hand thread

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
ALT723307
April 2010 1

Worksheet 7.2.1: Threads and Threading

3. ______ A type of thread that is a modified form of a square thread. It has a rounded crest
and root that form like a semicircle
a. Acme thread
b. Metric thread
c. Knuckle thread
d. American National thread

4. ______ Commonly known as the outside diameter, this is part of a thread is the largest
diameter of the thread on the screw or nut.
a. Lead
b. Pitch
c. Major diameter
d. Minor diameter

5. ______ The distance from a given point on one thread to a corresponding point on the next
thread.
a. Lead
b. Pitch
c. Major diameter
d. Minor diameter

6. ______ Commonly known as the root diameter. On a straight screw thread this is the
smallest diameter of the thread on the screw or nut.
a. Lead
b. Pitch
c. Major diameter
d. Minor diameter

7. ______ A tool for cutting internal threads. It has threads like a bolt with two, three, or four
flutes (grooves) cut across the threads.

a. Tap

b. Die

c. Helical tap

d. Solid die Perform Bench Work (Basic) Date: Developed Date: Revised Page #

Code No. April 2010 2
ALT723307

Worksheet 7.2.1: Threads and Threading

8. ______ This type of die is largely used for cutting external threads. The split of this die is
equipped with adjustment, varying the thread diameter and using more than one cut pass
may cut accurate threads.
a. Solid die
b. Die stock
c. Adjustable die
d. Split button die

9. ______ What will be the TDS for an M 10 x 1.5 tap?
a. 8.5 mm
b. 9 mm
c. 9.5 mm
d. 10 mm

10. ______ What tap is used for threading fully a hole up to the bottom. They have full threads
except for the first thread and are used to cut full thread as close as possible to the bottom
of a hole.
a. Plug tap
b. Taper tap
c. Bottoming tap
d. Tap wrench

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
ALT723307
April 2010 3

Information Sheet 8.1.1: Offhand grinding

Learning outcomes:
1. Cutter edges are honed and free of burrs.
2. Cutter is sharpened to conform to specifications.
3. Cutters are ground using appropriate cooling agents.
4. Cutting tool grinding is performed applying knowledge on safety procedures and using

personal protective devices.
Learning Activity:
8.1 Identify the different types of Off-hand grinders.
8.2 Describe the application of the different types of grinders.
8.3 Describe the application of the different types of grinding wheels.
8.4 Describe the procedure in grinding cutting tools.

Grinding
Grinding is the process whereby the piece of metal is being shape by bringing it to contact with
a rotating abrasive wheel

Grinding is used primarily for the following:
 To sharpen cutting edges on the drills, milling cutters, taps, and other cutting tools made
from hardened steel and other hard metals.
 As a machining process to cut metal to its desired shape and size.
 To make smooth polished surfaces as those required for bearings and on rolls for
processing various materials.

Types of Grinding Machines

There are two major types of grinding Non-precision and Precision grinding. Non Precision
grinding is also called is also called off-hand grinding. Metal removed by this method when
there is no great need of accuracy.

 Utility Grinders- Utility grinders are used for non-precision grinding operation done by
hand. Either the grinder or the work is hand held. Example of work done with the utility
grinder includes removal of sharp edges, and sharpening of tools.

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 1

Information Sheet 8.1.1: Offhand grinding fig. 8.1
fig. 8.2
Types of utility grinders

 Bench Grinder- a bench grinder is a small grinder
that can be bolted to the top of the bench. This
grinder is used for sharpening small tools and for
other light grinding.

 Pedestal grinder- it is a utility grinder mounted on
a free standing base, or pedestal. There are
various type of pedestal grinder, the heavy duty
ones using wheels 3 inches or more in width and
20 inches or more in diameter. The smaller
pedestal grinders are used for the same kind of
work as the bench grinder. While the larger type
are generally used for rougher type of work

 Portable grinder- Electricity or compressed air
powers portable grinders. They are often used for
delicate type of work such as grinding of dies.

fig 8.3
Types of precision grinders
In Precision grinding, metal can be removed with great accuracy. There are a number of
different precision tools grinding machines available that can grind metal parts to different
shapes and sizes with high accuracy.

 Surface Grinders- Surface grinding machine produces a smooth, true flat surface on parts.
Also, when the face of the grinding wheel is shaped to some special contour, from grinding
may be done with a surface-grinding machine.

 Cylindrical grinders- Plain cylindrical grinders are used in grinding the external surfaces
of sleeves pins rods and all cylindrical or tapered mechanical parts

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 2

Information Sheet 8.1.1: Offhand grinding

Grinding Wheels
Grinding wheels are the most important products made from abrasives, are composed of
abrasive material held together with a suitable bond.

fig. 8.4

Classifications of Grinding Wheel

1. Type of abrasive
 Aluminum oxide

Aluminum oxide is slightly softer but is tougher than silicon carbide. It dulls more quickly,
but it does not fracture easily therefore it is better suited for grinding materials of relatively
high tensile strength including all ferrous metals except cast iron.

 Silicon Carbide
Silicon carbide is extremely hard but brittle. It is suited for grinding materials that have a low
tensile strength (aluminum, brass and bronze) and high density, such as cemented
carbides, stones, and ceramics. It is also used for cast iron and most nonferrous and
nonmetal materials.
Have two colors:
Green silicon carbide is used mainly for grinding cemented carbides and other hard
materials.
Black silicon carbide is used for grinding cast iron and soft nonferrous metals such as
aluminum, brass, and copper; it is also suited for grinding ceramics.

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 3

Information Sheet 8.1.1: Offhand grinding

2. Abrasive Grain Size
The function of abrasive is to remove material from the surface of the work being ground. Each
abrasive grain on the working surface of the grinding wheel acts as a separate cutting tool and
removes a small metal chip as it passes over the surface of the work.

The sizing of the abrasive grain is rather an important operation since undersize grains in
wheel will fail to do their share of the work, while over sizing grains will scratch the surface of
the work Grain size in wheels range from 600 (fine) to 10 (coarse).

Abrasive grain sizes fig 8.5

3. Type of Bond
The function of the bond is to hold the abrasive grains together in the form of a wheel
Here are the common types of bonding materials:

 Vitrified Bond
The bond use in vitrifies wheels is a kind of clay. Vitrified bond wheels have large pores,
cut easily, and do not glaze (dull) easily. These bonds are suited to wheels use for rapid
removal of metal. They are not affected with oil, water, or acid that’s why it is suitable in all
types of grinding operations.
A wheel with a vitrified bond should be operated between 1920 and 1980 m/min.

 Resinoid Bond
Synthetic resins are used as bonding agents in resinoid wheels. Majority of resinoid wheels
are operated at 2895 m/min but can be ran faster up to 3810 to 6858 m/min. for faster
metal removal. These wheels are cool-cutting and remove metal rapidly. They are used for
cutting-off operations, snagging, and rough grinding.

Code No. Perform Bench Work (Basic) Date: Developed Date: Revised Page #
MEE722301 April 2010 4