Tapping

Tapping

Purpose: Cutting internal Threads

Condition or Situations for the Operation

Tapping is the process of cutting threads on a drilled hole by means of a
tool called tap.

A workpiece to be tapped in lathe is held and supported in a chuck or in a
steady rest. The operations can be done in two ways, namely Hand tapping
and Machine tapping. Hand tapping usually to tap blind holes while through
holes is done by machine tapping.

TOOLS, EQUIPMENT AND MATERIALS

1. Tools
1.1 Taps
1.2 Tap Wrench
1.3 T-Wrench
1.4 Independent chuck
1.5 Universal chuck
1.6 Spring loaded center
1.7 Paint brush
1.8 Spring cleaner

2. Materials
2.1 MS Drawing No. 108
2.2 25.4 x 190
2.3 Cutting oil

3. Equipment
3.1 Tapping attachment
3.2 Lathe machine

Figure 1. Set of Taps

Hand tapping in a lathe takes considerable time and is recommended to
be done when it is only absolutely necessary. On the other hand, machine
tapping in lathe requires just a very short time because of the use of a tapping
attachment.

Figure 2. Hand Tapping A Hole In the Lathe
Hole to be tapped must be drilled according to the Tap Drill Size (T.D.S.).
The depths of holes should be deeper then the length of the threads to be cut. It
allows the tap to reach the required length of the thread.
Task No. 1 – Tapping a Through Hole
1.1 Secure the materials and tools needed from the toolkeeper or

instructor
a. Check and replace damage tools with good ones
b. Study the blueprint of the workpiece

- Refer to Xs/Drawing No. 109
c. Check the workpiece

- Be sure that the hole is drilled and chamfered to specification
1.2 Clamp the workpiece in a chuck

a. Check if jaws are properly centered

Figure 3. Centering Chuck Jaws
b. Open chuck to the approximate diameter of the workpiece

Figure 4. Setting-Up Chuck Jaws
To Hold Workpiece

c. Clamp the workpiece securely
- Provide minimum overhang

Figure 5. Clamping The Workpiece In a Chunk
1.1 Select tap

a. Select a tap according to thread size on the blueprint
b. Check the sharpness of the cutting edge
1.4 Set-up the tap
a. Select a suitable tap wrench and fit the tap
b. Mount a spring loaded center in the tailstock spindle

Figure 6. Setting up A Spring Loaded
NOTE: Spring loaded center is use to ensure that the tap enters the

hole squarely. If a spring loaded center is not readily
available, an ordinary lathe center may be used to keep
pressure by winding in the center, as the tap wrench is
turned.
c. Apply cutting oil on the tap with a brush

Figure 7. Applying Cutting Oil to relieve cutting Friction Between Tap
and Hole

d. Insert the tapered end of the tap into the drilled hole.

Figure 8. Setting-Up Tap Into the Hole

e. Firmly hold the tap wrench with the left hand and move the
tailstock to locate the center on the end of the tap

Figure 9. Locating the Corner on Tap end
f. Rotate the tailstock handwheel to apply pressure on the tap.

Figure 10. Applying Force On Tap Through the Tailstock Center
1.5 Tap the hole

a. Turn the tap wrench about two full turns in a clockwise direction

Figure11. Tapping The Hole

b. Turn the tap about half a turn in a counter clockwise direction to
break chips and prevent the tap from jamming in the hole

Figure 12. Relieving the Hole With chips
c. Repeat the process of turning the tap about two turns, then

revising for a half turn, until the hole is tapped
1.6 Check the thread

a. Clean the tapped hole to remove chips
b. Check the thread with a thread gauge.

Figure 13. Checking the Tapped Hole

NOTE: If a blind hole will be tapped, the hole must be drilled 2.3 deeper
that the required length of full thread. In setting-up the tap, the
distance from tap wrench to end of tap is measured. The depth of
hole is subtracted from the distance which give the distance from
end of workpiece to tap wrench

Figure 14. Tapping A Blind Hole

Task No. 2 – Tapping a Hole using a Tapping tools needed from the
toolkeeper or instructor

2.1 Secure the materials and tools needed form the toolkeeper or
instructor

a. Check and replace damage tools with good ones
b. Study the blueprint of the workpiece
c. Check the workpiece

- Be sure that hole is drilled and chamfered to specification
2.2 Clamp the workpiece in a chuck

a. Check if jaws are properly centered, refer to figure 3
b. Open chuck jaws to the approximate diameter of the workpiece,
refer to Figure 4
c. Clamp the workpiece securely, refer to figure 5.

- Provide minimum overhung
2.3 Select tap

a. Select a tap according to thread size on the blueprint
2.4 Set spindle speed

a. Check machine speed plate and set nearest speed
- Speed to be used should be based form the material of the

workpiece

Figure 15. Setting the Speed of Machine
2.5 Set up[ the tap

a. Mount the tapping attachment in the tailstock spindle

Figure 16. Setting up Tapping Attachment in the Tailstock Spindle
b. Clamp the tap in the attachment and tighten

Figure 17. Mounting The Tap in the Tapping Attachment

c. Set friction device for thread size

Figure 18. Adjusting The Attachment Thread Size
2.6 Tap the hole

a. Bring the tailstock forward so that the tap is close to the hole

Figure 19. Setting-Up the Tap Into The Hole
b. Clamp the tailstock
POSITION GUARD WEAR SAFETY GOGGLERS
c. Start the spindle
d. Arrange the flow of cutting oil into the hole
e. Feed the tap forward using the tailstock spindle

Figure 20. Tapping The Hole

f. Stop and reversed the spindle when the thread is cut
- Be sure that the spindle is stopped and reverse before
the tap is disengage from the thread

g. Wind the tailstock spindle back to remove the tap as when it
enters the hole\

h. Stop the spindle
2.7 Check thread

a. Clean the hole with a spring cleaner
b. Check the thread with a screw plug gage

Figure 21. Using A Screw Plug Gage To Check A Tapped Hole

Precaution

IMPORTANCE

1. Clean the tools and machine before and after using.
2. Place tools inside the tool box when not in use.
3. Maintain correct oil levels of machine parts and gear mechanisms.
4. Always make sure that part are tightly connected or bolted.

TEST REVIEW EXECRCISES

Select the best Answer. Write the letter of the correct answer o the blank
provided before each number.

_________ 1. The process of cutting threads on the surface of a hole using a tap
is called

a. screw cutting
b. reaming
c. tapping
d. boring
__________2. The tool used in tapping a hole is called
a. reamer
b. twist drill
c. screw pitch gage
d. tap
__________3. Hand tapping is performed on the lathe to tap
a. blind holes
b. through holes
c. tapered holes
d. recessed holes
__________4. Machine tapping is performed on the lathe
a. tap
b. through holes
c. blind holes
d. recessed holes
__________5. To perform machine tapping the tap is held in
a. t-tap wrench
b. adjustable tap wrench
c. tapping Attachment
d. drill chuck

Direction: This form should afford the Instructor to rate the

Productivity/Performance of the trainee for a give Employable

Skill/Activity/Project. On the space provided for, write the points which likely
coincide with your evaluating for each of the following factors: Outstanding – (4
pts.); Plus Satisfactions – (3 pts.); Satifactory - (2 pts.); Below Satisfactory –

(1 pt.)

SATISFACTORY TASK PERFORMANCE REQUIREMENT FACTORS Ra
g

Give the blueprint of the workpiece, complete tools and materials A. Quality/Appearance
the trainee must be able to:
(symmetry; Verticality;
1. Tap a blind hole Horizontality ;
2. Tap a through hole Workmanship,
Finish)………….
B. Accuracy/Criticality

(Exactness of
dimension/specification,
High, Medium, Low
criticality

C. Speed (50% over
estimated time . . . – (1
point) (50% time save
over estimated . . . and (1
point) . .

D. Method (Economical:

use of tools ; Safety and
hygiene, Initiative)
…………….

TOTAL POINTS …………….. _____
GRADE ………………………._____

REMARKS: Working hours is approximately one (1) hour.

By:___________________________

____________________________
Designation