10% rule for runout inspection fixture

[Raddy13]

I'm working on an inspection fixture for a shaft that has a 0.02 Runout called out on the drawing. I'm not experienced in designing inspection gages and fixtures, so I've been reading up on it and I came across the 10% rule, that inspection gage tolerance should be about 10% of the tolerance it is inspecting. I understand how it applies to things like plug gages, so does that also mean that the spindle which will hold the part should have a Runout tolerance of 0.002?

 

[dgallup]

10% rule mostly applies to the gauge itself so assuming you are using a dial indicator then it needs to have markings showing 0.002 or less. However, the entire measurement system needs to pass a GR&R so the spindle needs to have good runout too. Typically the spindle would be much better than 0.002.

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[Raddy13]

Ah good point, thank you. Is there a guideline for how much runout tolerance I should require for the spindle based on our callout?

 

[3DDave]

Recall that if the part is within less than 10% of the margin you have unfortunate option to accept out of tolerance parts.

 

[dgallup]

What is you process capability? How many good parts do you want to throw away?

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[Raddy13]

Actually, now that I'm thinking about it, shouldn't the spindle runout just be below the measurement error of the dial indicator?

 

[dlinthicum]

Take a look at Y14.43.
Dimensioning and Tolerancing Principles for Gages and Fixtures.