Cutting Internal Thread

1. Mechanical Engineering
Technology
Topic: Internal Screw Thread Cutting.
Objectives : Students should be able to:
• Define internal screw thread.
• State explain the uses of taps
• Calculate tap size drill.
• State precautions associated with screw thread
cutting.

2. Cutting Internal Threads
Internal threads are made by using a tap.
Taps are made of Carbon Steel or High
Speed Steel (HSS) and are carefully
hardened and tempered for long life.
Taps are quite brittle and are easily
damaged if not handled properly.

3. Internal Threads

4. Taps are usually made in sets
of three
• Taper Tap
• Second or Intermediate Tap
• Plug or Bottoming tap

6. TAPER OR FIRST TAP

7. SECOND OR INTERMEDIATE

8. PLUG OR BOTTOMING TAP

9. Tools used for holding Taps
Adjustable Tap Wrench

10. Chuck Pattern Tap Wrench

11. How to use wrench and tap together.

12. INTERNAL SCREW THREADS CUTTING
STEPS
1. A hole must be drilled. This hole is called Tapping Size Hole.
Formula= D-P
where D= Major Diameter
P= Pitch
Example- M10 * 1.5
Tapping Size= 10-1.5
=8.5mm
2. Clamp work securely in a bench vice, level and square.
3. Make clockwise turns to start the threads and anti-clockwise turns to break
the chip
4. Oil must be used to lubricate the threads.

13. Care in Tapping
 Considerable care must be exercised when
tapping.
 Use the tap before the die because the
taps are non-adjustable for size, the dies
are
 Start the tap square.
 Use a cutting solution where necessary.

14. Care in Tapping Cont’d
 Ensure that a blind hole is drilled
deeper than the depth of thread
required to allow clearance for
chipping.
 Do not force a tap to cut. Remove the
chips as necessary.

15. Internal THREAD
HEX NUT 25
M10x1.5

16. True or False
 Taps are made in sets of 3.
 Taps are made of high tensile steel.
 Taps are usually very brittle.
Quiz Time

17. Quiz Time
Identify the taps shown below

18. Quiz Time
Identify the tap shown below

19. Quiz Time
Identify the tap shown below

20. Quiz Time
Identify the tool shown below