Method for holding Stock

[Chaz]

I am milling some gears from various types of plastics - one of the gears needs machining on both top and bottom. Obviously when I take the part out to turn it over, I struggle to get it perfectly aligned - I was thinking of making some kind of a jig - not sure.

Is there a holding device that allows you to flip a part over and still have it perfect based on where the previous centre mark would have been?

Thanks

[Spedley]

Could you not just machine a couple of dowel holes through the part into the table before you cut it, then flip it and dowel it again?

[Chaz]

That is one option - I could also use a set of right angled sections but the issue is that the item is round and you ideally need to have it not rotate either.

[irving2008]

Surely if its a gear the central hole and/or boss plus an offset dowel hole would both register and locate it.

[Spedley]

Or perhaps cut the back side first and leave a spur with dowel hole which is cut off on the front side.