1. EML 2023 – Threads and Fasteners
Lecture 1 - Nomenclature

2. Thread Terminology

3. Thread Callouts - Metric
(mm)
(mm)
(mm)

4. Thread Callouts – ANSI Unified
1 – loosest fit
2 – normal fit
3 – most exact fit
B represents internal thread
(in)
UNC – Unified National Course
UNF – Unified National Fine
UNEF – Unified National Extra Fine
UN – Unified National

5. Thread Callouts – ANSI Unified
Assumes course threads with a nominal fit (2).
(in)

11. Goal:
connect the top part to the bottom part using a #10-24 cap screw which has a head taper of 82˚
must determine length of screw

12. Steps:
buy the screw
drill a countersunk hole without threads (clearance hole) into the top part
drill a threaded hole in the bottom part

14. 2 things to know if you tap a hole
the thread length should be at least twice the diameter of the fastener
if you use a bolt to connect some bodies
the bolt should extend beyond the nut by at least two thread pitches
How long should the screw be?

15. the major diameter of the #10 screw is  .190”
the length of the screw must be at least as long as
.30” + 2.19” =.68
will purchase a #10-24 screw that is .75” long

16. The major diameter of the screw is .190”.
What should the diameter of the clearance hole be?

17.
Engineer’s Handbook

20. Was able to download a SolidWorks part file of this cap screw.

21. A clearance hole has been created for a #10 flat head screw with an 82˚ head taper.

22. A tapped hole for a #10-24 screw.
The screw we selected is .75” long. Therefore the thread depth of the hole must be at least .75”-.3” = .45” deep.
I selected a thread depth of 0.45” and a pilot hole depth of .66”.

23. If you only tap the blue body to the recommended depth of 2 major , i.e. .38”, you will have the following.

24. 2nd Example Problem
3/8” – 24 cap screw
blocks are 1.5”1.5”.50”

25. 2 things to remember if you tap a hole
the thread length should be at least twice the diameter of the fastener
if you use a bolt to connect some bodies
the bolt should extend beyond the nut by at least two thread pitches

26. Determining Bolt Length

29. Bolt length calculation
Bolt must be 1.988” long plus the distance of 2 extra pitches.
The bolt has 24 threads per inch. Two extra pitches will require an extra 1/12” of an inch.
Total minimum length is = 2.071” .
Find the next longest available bolt.
.50”
1.988”
.08”
21/64”

30. 2 things to remember if you tap a hole
the thread length should be at least twice the diameter of the hole
if you use a bolt to connect some bodies
the bolt should extend beyond the nut by at least two thread pitches