Bore and OD center indicator for the mill.

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thegallery

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I do not need to find the center of a bore or center of an OD often enough to justify an expensive coaxial indicator such as a Blake. Then there is the argument about the accuracy of coaxial indicators. I decided to build my own tool for the mill. This is the design I came up with. The geometry makes it very accurate. There is no co-sine error since the trace finger is symmetric. It seems to work great.
 

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trlvn

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That is really nice. You wouldn't have drawings or even sketches would you? I'm particularly interested in the pivot between the dial indicator and the part being measured.

Thanks for posting!

Craig
 

thegallery

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The axial for the pivot arm is design so the distance to the work (ball end) from the pivot point and the distance from the pivot point to the push rod on the indicator are equal, in my case it is 1". Since it is a one to one ratio the indicator reading is accurate unlike on a Blake coaxial indicator. I do not have any drawings, I am one of those weird guys that never uses plans everything is in my head. The key to this design is that you are measuring the actual radius length not an indirect measurement. Spindle run out will not effect the reading.
 

SmithDoor

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This what like using


Dave

I do not need to find the center of a bore or center of an OD often enough to justify an expensive coaxial indicator such as a Blake. Then there is the argument about the accuracy of coaxial indicators. I decided to build my own tool for the mill. This is the design I came up with. The geometry makes it very accurate. There is no co-sine error since the trace finger is symmetric. It seems to work great.
 

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