Mechanical hardware

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

Common types of external fasteners

1. Machine Bolt & Screw

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

Grade Chart

Grade Chart (cont.)

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

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

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

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

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

7. Thumb and wing screws

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

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

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

11. Pins & Keys

Flat Washers

Lock Washers

Lock Washers (cont.)