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Why do they do these things? Tru-position


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We have a shaft about 9 inches long. On the end of the shaft there is a bore with a tru-position callout to -A- (the shaft) of .00196".
I was called on Saturday at 8:00 AM by my panicked boss..." I can't do this! What am I going to do !! " . I told him to put the part in a vee block locating on the shaft and indicate the bore, It should be less than .00196". Twenty minutes later the owners son says we NEED to Check tru-position !!!.

So on Monday I fire up and check it with the micura. Add a max material condition per print and look at the print out.

So how does adding MMC change my actual value????

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The .(M) is not the Position result, but merely a statistical value used to display tolerance usage for capability analysis.

You cannot calculate capability on a tolerance with a material boundary because every part has a slightly different tolerance. That is why it is converted to a percentage of tolerance usage.

If you take the result of 0.000534 and divide it by 0.002368 you get .2255 or 22.55%. If you take the .(M) result of 0.000444 and divide it by 0.001969 you get 0.2255 or 22.55%.

At the end of the day, you can disregard the .(M) result. There are multiple posts on the forum on how to remove it from the printout.
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What in the world are you making that has a nominal diameter of .629133" and tolerance of .00196" instead of .6291" and .00195"?

What's the uncertainty ratio of your Micura?

Jeff Frodermann
Meier Tool & Engineering
Brooklyn Park, Minnesota


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I don't think Dave was referring the (M) in his original post. Maybe he was. He just wasn't clear with his question.
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[/quote]

I don't think Dave was referring the (M) in his original post. Maybe he was. He just wasn't clear with his question.
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That was what I was talking about, and the answer is good. BUT, I get frustrated when they don't understand that not EVERY stinking thing has to go thru our CMM's . The tir check was sufficient. stop calling me on my days off ! 😠 😠 😠 🤣
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Come on, Dave. Aren't you a team player? Don't you feel valued when your team looks to you for help?


Jeff Frodermann
Meier Tool & Engineering
Brooklyn Park, Minnesota

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