1. Mechanical hardware

2. Strength minimum thread engagement = to the dia. of the thread
1.5 times is best
it is better that the screw breaks and not the threads slipping

3. Common types of external fasteners

4. 1. Machine Bolt & Screw

5. Grade markings for bolts
bolt head markings
often (but not always) grade is two more than number of marks

6. Grade Chart

7. Grade Chart (cont.)

8. 2. Stud bolts
threads on both ends
manifolds, etc.

9. 3. Carriage bolts used to fasten wood and metal parts together
square body

10. 4. Machine screws general assembly head is slotted for screwdriver
identified by 2 methods
fractions (1/4” and above)
numbers (below 1/4”)

11. 5. Cap screws used where precision is required
have a finished appearance

12. 6. Set screws used to lock pulleys, collars, on shafts etc.
square and socket head

13. 7. Thumb and wing screws

14. 8. Thread forming screws used for assembly, sheet metal, etc.
they form threads, they do not cut material
require an existing hole

15. 9. Internally threaded fasteners
common hex or square head nut is most common
identified by the size of the bolt they fit

16. 10. Internal thread inserts
repair a damaged or stripped internal thread

17. 11. Pins & Keys

18. Flat Washers

19. Lock Washers

20. Lock Washers (cont.)