gear pitch cone as a datum

[don0000]

I have a die cast miter gear that gets bore and back face machinied.If I use the gear pitch cone as a datum for machining does this give me primary datum (cone axis) and secondary datum (apex point) for dimensioning from?

 

[drawoh]

don0000,

A cone axis and cone apex do not exist, and therefore are not valid datums. You can fixture on the gear teeth if you do not mind using them to locate the part while it is machined. If you can figure out a fixture to the mitre gear teeth, you have centre and axial location.

A good quick and dirty rule about datums is that you should be able to visual the fixture that attaches to them.

JHG