Acme threads

Square threads

Buttress threads

Multiple threads

pulley is made the weakest

key is made the weakest

key is made the stongest

all the three are designed for equal strength

4 mm

5 mm

6 mm

7 mm

knuckle joint

cotter joint

oldham coupling

universal joint

only to the pinion

only to the gear

to stronger of the pinion or gear

to weaker of the pinion or gear