1. Copyright © Texas Education Agency, 2014. All rights reserved.
Screw Threads
Copyright © Texas Education Agency, All rights reserved.

2. Copyright © Texas Education Agency, 2014. All rights reserved.
Screw Thread Uses
Fasteners
Adjusters
Transfer Power
Mechanical Advantage
Copyright © Texas Education Agency, All rights reserved.

3. Copyright © Texas Education Agency, 2014. All rights reserved.
Screw Thread Uses
Fastener – (bolts, nuts, and screws) used to hold parts together
Movement – (lathe lead screw) transmits twisting power to straight line motion
Mechanical advantage – (vise and clamp screws) increases force to hold items
Adjustments – allows parts to be moved
Copyright © Texas Education Agency, All rights reserved.

4. Simple Definition of a Thread
A screw thread is a wedge wrapped around a cylinder.
Copyright © Texas Education Agency, All rights reserved.

5. Copyright © Texas Education Agency, 2014. All rights reserved.
Fine Thread
Right Hand
Coarse Thread
Left Hand
Square Thread
Metric
Pipe Thread
ACME Thread
Internal
External
Copyright © Texas Education Agency, All rights reserved.

6. External and Internal Threads
External Threads are on a bolt.
Internal Threads
are in a nut.
Copyright © Texas Education Agency, All rights reserved.

7. Copyright © Texas Education Agency, 2014. All rights reserved.
Right-Handed Bolt
All bolts and nuts are right handed unless marked.
Right-handed threads tighten by turning clockwise.
Left-handed threads tighten by turning counter-clockwise.
Copyright © Texas Education Agency, All rights reserved.

8. Copyright © Texas Education Agency, 2014. All rights reserved.
Thread Size
Threads are sized by the diameter of the bolt and the number of threads per inch.
Copyright © Texas Education Agency, All rights reserved.

9. Copyright © Texas Education Agency, 2014. All rights reserved.
Threads per Inch
A ¾” – 10 bolt has
10 threads per inch.
Copyright © Texas Education Agency, All rights reserved.

10. Copyright © Texas Education Agency, 2014. All rights reserved.
Standard Thread Sizes
Coarse Threads
¼” – 20
³∕₈” – 16
⁷∕₁₆” – 14
½” – 13
⁹∕₁₆” – 12
⅝” – 11
¾” – 10
Fine Threads
¼” – 28
³∕₈” – 24
⁷∕₁₆” – 20
½” – 20
⁹∕₁₆” – 18
⅝” – 18
¾” – 16
Copyright © Texas Education Agency, All rights reserved.

11. Copyright © Texas Education Agency, 2014. All rights reserved.
Metric Threads
Metric threads are sized by diameter and thread pitch in millimeters.
The coarse metric threads use only the diameter size (example, M10).
The fine metric threads will have the diameter and pitch size stated (example, M10 X 1.25).
Copyright © Texas Education Agency, All rights reserved.

12. Copyright © Texas Education Agency, 2014. All rights reserved.
Standard Metric Sizes
Coarse Threads M6.3 X 1 M8 X 1.25 M10 X 1.50 M12 X 1.75 M14 X 2 M16 X 2 M20 X 2.5
Fine Threads
M6.3 X 0.75
M8 X 1
M10 X 0.75
M12 X 1
M14 X 1.5
M16 X 1.5
M20 X 1
Copyright © Texas Education Agency, All rights reserved.

13. Copyright © Texas Education Agency, 2014. All rights reserved.
Types of Threads
Standard threads are V-style with 60° angles.
Copyright © Texas Education Agency, All rights reserved.

14. Copyright © Texas Education Agency, 2014. All rights reserved.
Types of Threads
Square Threads are square in shape, with the same width and depth.
Copyright © Texas Education Agency, All rights reserved.

15. Copyright © Texas Education Agency, 2014. All rights reserved.
Types of Threads
ACME Threads are like square threads, but with a 29° angle on the sides; they’re used to transfer power.
Copyright © Texas Education Agency, All rights reserved.

16. Copyright © Texas Education Agency, 2014. All rights reserved.
Types of Threads
Pipe Threads are tapered; the back is shallower than the front of the thread.
Copyright © Texas Education Agency, All rights reserved.

17. Basic Thread Terminology
A. Major Diameter
B. Pitch Diameter
C. Minor Diameter
D. Crest
E. Root
Copyright © Texas Education Agency, All rights reserved.

18. Basic Thread Terminology
A. Major Diameter- the largest diameter of a bolt at the crest, or the diameter of the roots of a nut.
B. Pitch Diameter- the diameter halfway between the major diameter and minor diameter.
C. Minor Diameter- the small diameter of a bolt at the root, or the diameter of the crest of a nut.
Copyright © Texas Education Agency, All rights reserved.

19. Basic Thread Terminology
D. Crest- the top surface where the two sides of the threads meet.
E. Root- the bottom surface where the two sides of the threads meet.
Crest
Root
Copyright © Texas Education Agency, All rights reserved.

20. Basic Thread Terminology
Copyright © Texas Education Agency, All rights reserved.

21. Basic Thread Terminology
Pitch- the distance between thread crests of the thread.
Height- the measurement from the root of the thread to the crest of the thread.
Slope- the angle of the side of the thread.
Copyright © Texas Education Agency, All rights reserved.

22. Copyright © Texas Education Agency, 2014. All rights reserved.
Assessment
Quiz
Cut 10 different sizes of internal and external screw threads using a set of tap and die, or lathe and tap.
Copyright © Texas Education Agency, All rights reserved.

23. Copyright © Texas Education Agency, 2014. All rights reserved.
Reference
Oberg, E. (2012). Machinery’s handbook, 29th. South Norwalk, CT: Industrial Press, Inc.
Threads and Threading: pages
US Standard Screw Thread: page 1806
Definitions: pages
Metric: pages
Acme: pages
Square: page 1944
Pipe: pages
Copyright © Texas Education Agency, All rights reserved.