Generator slip ring machining - How to best test surface finish on a tightly and interrupted surface

[racookpe1978]

The spec's require a nbr 8 finish on a the generator slip rings after they have been remachined in the field, but the rings are a "wound spiral" only 5/16 wide wrapped around a 16 inch diameter shaft.

So the surface I'd be trying to check the finsih on is a tight spiral with 5/16 inches of honed steel, a 3/16 gap, then the next spiral of 5/16 width. Since the whole spiral is wrapped around the small diameter shaft, I know I can only check a small part of each loop at a time. this certainly isn't a long flat piece of steel!

Do I have to use a visible gage and try to compare each spiral with the surface by eye and flashlight, or will an automatic tester work and not be thrown off by the grooves between each polished area?

 

[MikeHalloran]

A sample surface finish gage and a fingernail should be good enough. You can do it in the dark.



Mike Halloran
Pembroke Pines, FL, USA

 

[racookpe1978]

Used the latter.

And a LED flashlight. 8<)