# Opinions on how to measure ID's on bores?



## Sandia (Aug 15, 2014)

I was wondering what the general perferred tool for measuring bore diameters. I have a set of Starret telescoping bore guages but was wondering if there is anything better? Seems to me like on some bore diameters the edge of the anvil on the gauges contact the wall of the bore before the center of the anvil does. Maybe thats the way they are designed ? Any advice appreciated.

Bob


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## chuckorlando (Aug 15, 2014)

Mine have a radius on the tip so the point touches. I just do multiple checks in multiple places around the bore. If you wanted it to be right on you would use a dial bore gage or even better a triple point dial gage I would think.


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## awander (Aug 15, 2014)

Any Small Hole Gage worth anything will have the ends radiused smaller than the radius of the smallest hole it fits in.


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## zmotorsports (Aug 15, 2014)

awander said:


> Any Small Hole Gage worth anything will have the ends radiused smaller than the radius of the smallest hole it fits in.



^^This.  The snap gauge should have enough of a radius on it that the centers is what comes in contact with the ID of the bore.

I use telescoping gauges and expanding style gauges for smaller holes.  If i have multiple holes I am measuring, I get out the bore gauge.  When using the telescoping gauges, take multiple snap tests and look for consistency.

Mike.


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## Fabrickator (Aug 16, 2014)

I use telescoping snap gauges for any bore over 1/2".  When using a snap gauge, be sure to snap it out on a slight angle and then roll it out,while wiggling to be sure your centered to get the best measurement, and do it at several places around the bore to check for repeatability.  They will get you as close as is needed for most any fit.


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## Tom Walter (Aug 16, 2014)

Sounds like you are measuring some small holes!

Under 0.750" - Pin Gauges (minus).   They are sold in .001" increments.  Minus means 0.000 0 to 0.000 2" undersize.
You can get a really good feel for the bore size.  (I have set up to 0.500",  above that I make up my own on the lathe
and mic as needed, but really need that 0.500 to 0.750" set)

Just handy to have in a shop for checking unknown holes.


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## Sandia (Aug 16, 2014)

Thanks for the advice fellows. The Starret set of snap gauges I have, the anvil is rounded and I follow the procedure mentioned above when measuring. I usually check about 3 to 4 times and then average the numbers.

If I wanted to purchase a dial bore indicator, give me some guide lines on what to purchase, please.

Thanks, Bob


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## Rick Leslie (Aug 17, 2014)

Depending on the ID diameter, I usually use snap (telescoping) gauges. For smaller holes I'll use the round ball (technical name?) gauges. If it really has to be dead nuts, I use pin gauges.


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## kd4gij (Aug 19, 2014)

For anything over 1 1/2"id I use a bore mic. and use an od mic to verifi.


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