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darryl
03-15-2007, 01:21 AM
Anyone ever make their own indicator? I'm thinking of making one with a wheel that would touch against the workpiece (in lathe chuck) and just roll as the spindle is turned. Through some leverage it would amplify its deflection and move a needle across a scale. It would be for centering only and as such it wouldn't need calibration, just the ability to show deviation. It would be spring loaded so the wheel can move back a fair amount without damaging the mechanism, but before hitting the spring, it would give a reading over a small range, like maybe 20 thou (just a figure).

I got the idea for this after I finished with the cathead. I realized that if I centered something in the cathead using bolts of exactly equal length, I could indicate off the bolt heads and not have to indicate off the piece that I'm trying to center. Testing this theory with a typical dial gauge shows that it works well enough, but you have to be so careful with the indicator. I'd rather be able to just roll the spindle by hand and let the wheel ride up on the boltheads as they come around. Sure, you have to play with the spindle position to get the readings off the same spot on each bolt head, but that's fast and easy to do.

This make any sense to anybody?

Marc M
03-15-2007, 01:54 AM
I understand what you're wanting to do. I wouldn't waste time making an indicator. Instead, design a mechanism that incorporates a standard indicator for the gage portion. The gage tip would ride on your wheel assy. to detect it's deflection. Use a spring loaded adjustable stop that will limit the distance the gage tip can travel while allowing the wheel to move further. Hopefully you understand what I'm explaining so poorly here.

Marc -

darryl
03-15-2007, 02:02 AM
Yes, I understand that Marc- thanks for the idea.

BobWarfield
03-15-2007, 10:44 AM
darryl, I have a vague recollection of having seen something like this, intended for another purpose. There are gages as well as clamps and centering devices that work by using 3 circular pieces in a triangular configuration. I wish I could remember more about what I'd seen, but they had some means whereby rotating a single shaft would rotate all three discs on an eccentric hub that would make the center hole closer or further and thereby clamp or measure.

I know I have seen these sold commercially, and also on someone's web site they built one.

Best,

BW