Measuring ID's: Which is the most accurate? CMM / Sunnen Gage / Plug Gage?



Standard Rule of Thumb:
Most accurate gage for checking an ID for accuracy: CMM vs Sunnen Gage vs Plug Gage. Any thoughts?

Al Dyer

I'm not familiar with a sunnen gage but I would tend to choose the CMM over a plug gage. When using a manual plug gage there is a higher degree of operaror bias. MHO


[This message has been edited by Al Dyer (edited 24 March 2001).]


I need to know the application (size, tolerence)to recommend the best method. Typically for checking parts the CMM or the Sunnen are good for +/- .0001". Some Cmm's can do better then others. In a production application the Sunnen wins hands down. If you are trying to calibrate plain ring gages, I use a Federal internal comparator. our uncertainty is +/-.000009"+1.5 X L.



Of the 3 instruments you mentioned I would choose the Sunnen gage. As was mentioned the plugs have more operator bias than the Sunnen or the cmm. Recent uncertaintity analysis on one of our LK cmms was .000182 x 2.1 L. We have a sunnen gage and I can attest That they are better that the other two.
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