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Root diameter incorrect.


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Hello everyone,

I am inspection a gear with a Root Diameter of .1528-.1485 inches. I have measured all 5pcs on Gear Pro and gotten everything from .1632-.1643. I have put them on our comparator and they measure .1520-.1528.

I have double checked the the probe and it isn't loose, and have qualified it and have measured a ring gage and all dims are correct. I verified the part isn't moving either. Have also qualified the rotary table several times as well. What am I missing?

Thanks,

Lou

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Lou,  strange, sometimes you may get a smaller than actual size due to probe ball not clearing the full root, but I would agree this one makes no sense.

what size ball are you using, what size is the root radius? is it full or fillet?  Is this a gear or spline ?

 

Did you measure TIP diameter ? Did this measure ok ?

 

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The most common issue I see with Root Diameter measurements is if it is a flat bottom root, and you leave Self-Centering on, it will sometimes roll into the corner radius of the root/flank and take the measurement there. Which is why I typically turn off the Self-Centering unless it is a full radius. 

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Chris, 

I am using a .5mm ruby. And it's Root radius fillet of .0065 of an inch. So, I'm guessing my probe is too big?!?!?  And yes I am measuring the tip and it is coming up undersized as well. Tip dimensions are .310 +0.0 / -0.001. Measurement is .307. 

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sounds like a probe issue, is probe bending? can you try replacing the ball ?

Have you confirmed the Tip Dia in Calypso ? The ball does seem too big for the small fillet, but it doesn't tell us how much space is in the root area, may possibly still clear.

Is there possibly a flat on the ruby ? Are you measuring all gear test with this same probe tip ?

 

 

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Chris,

If the probe is bending I cant visibly see it. I have replaced the probe and have gotten same results. Tip diameter is .503mm. There does seem to be enough space in for the size of a probe. And there isn't a flat the on the ruby. Lab let me use there microscope not sure the magnification but the ruby is not flat. And I am measuring the all the gears with same probe. 

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WRONG on the space for the probe. The probe is to big for these gears. I think even a .2mm may be too big but the company is willing to buy a few probes. So we will see. 

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