40" Shoulder to shoulder gage

[kenjbro77]

I am needing to hold a dimension 39.850" +/-.001". It is on a 4.375" O.D. Rod. Each end gets turned down to 4" O.D. So I have only .1875" shoulders. I need to hold the distance between shoulders to 39.850 +/-.001. The overall length is 64.225" I need to find a way to measure this in the machine.
Thanks,
Kenneth

 

[BillPSU]

A custom gage with a fixed measuring anvil on one end and a micrometer head or indicator on the other end. You will need a standard to calibrate the gage. Meeting the 10 times accuracy requirement for a gage will be your greatest problem if you need to meet your in-house quality guidelines. I question the +/-.001 dimensional tolerance. Could you machine and then shim to the correct length?

Bill

 

[kenjbro77]

The problem with a micrometer head is the .1875 between the 2 o.d. diameters. Using shims is not an option as this is a part we are machining for a customer.

 

[BillPSU]

Ask your customer how they check the part and borrow their gage. Master Vernier Caliper another choice but this will cost about $3000. Probably a lot more money than the part is worth. Be sure the temperature is correct as temperature variation will cause problems for this length.

Bill