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Re: Micrometer responses

To: Dave Williams <dave.williams@chaos.lrk.ar.us>
Subject: Re: Micrometer responses
From: Phil Ethier <ethier@freenet.msp.mn.us>
Date: Wed, 18 Dec 1996 00:30:49 -0600 (CST)
On Tuesday, 17 Dec 1996, Dave Williams wrote:

> -> T-gauges are neat, and a whole lot more accurate than one might
> -> think, but they can be fooled.
> 
>  I have a two-point dial bore guage.  The old T-guages are actually
> easier to use.

Oh, my, yes.

> -> They only measure at two points, and you can
> -> miss an out-of round condition.
> 
>  How else are you going to find an out-of-round condition?  You turn the
> guage 45 or 90 degrees and measure that way.  The difference tells you
> out of round.

If the OOR condition is oval (two-lobe) as typical in a car cylinder.  If 
it is three- or five-lobed as from a twist drill, you may never see it 
with a two-point measuring device.  That's when you need that three-point 
bore gauge or a radial indicator setup.

Phil

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