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Re: Machinist / measuring help

To: Lester Ewing <lewing@sport.rr.com>
Subject: Re: Machinist / measuring help
From: John Caffrey <jdc6@Lehigh.EDU>
Date: Fri, 16 Feb 2007 10:29:40 -0500
Lester Ewing wrote:
> Good morning all,
>
>     I have a minor dilemma.  I am trying to measure the bore of one of 
> my 2 stroke engines (Bullnose) and I have several measuring tools but 
> I don't know the "trick".  That is to say that I have telescoping 
> guages, internal micrometer, calipers, and micrometers but in all of 
> that I can't figure out how to insure that the internal mic is in the 
> proper plane for measuring the cylinder bore.  As this tool, and the 
> telescoping guages too, can be horizontally and vertically from an 
> ideal plane (which would give max and correct diameter) I don't get 
> the measurements correct.  I know this because according to my 
> measurements the pistons should not fit in the cylinders yet they do..
>
> .. so how does one really measure the cylinder bore?
Hi Lester,
Using the inside mike takes some practice, but you pivot it on one end 
while sweeping an arc in the horizontal plane and adjusting it. You then 
sweep through the vertical plane to feel the measurement. It helps if 
you have a handle for the mike. An easier method is using a dial bore 
gage. You calibrate the bore gage to a ring gage or outside mike, and 
then using a sweeping arc vertically you can read the deviation in ten 
thousands (0.0001") from your setting. This is the tool that most engine 
builders use.There are other tools but they're usually only seen in in 
production inspection departments, i.e. tri-mikes, air gages, etc.
John
Fogelsville, PA




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