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Old 09-02-2009, 06:10 PM
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Earthman Earthman is offline
Motorized Bicycle Senior Member
Join Date: Mar 2009
Location: Pittsburgh, PA
Posts: 82
Default Re: Manic Mechanic sprocket adapter

Originally Posted by Buddy View Post
That's what I've been using. I keep getting a different reading every time though. It doesn't help that the battery is about dead I think and the display is dim and flashing constantly. They aren't mine, mine aren't accurate enough.
Replace the battery. Practice taking readings on something more accessible and that you know is a uniform thickness. The caliper has to be perpendicular to the surface you are measuring and the amount of force you use to close the jaw has to be about the same for each reading to get repeatability from one reading to the next. Use the flat part of the measuring jaw, not the part of the jaw near the end that has been sharpened to a knife-like edge (it's too easy to tilt the caliper from perpendicular and get a different reading). Keep the flat part of the jaws tight against the surface of the hub.

Assuming the electronic caliper is working (it likely is), and you have a cylindrical hub, take 10 readings in different places, add them, then divide by 10 to get an average. Each of the 10 readings shouldn't vary by more than a few 0.001's if the hub is cylindrical, you are consistent in how you take the readings and are doing it right.

It's likely that the hub adapter will be machined slightly larger than the dimension you provide. Maybe by 0.01" or so. Consequently, it may not matter much if your readings are off by +/-0.005". Ask the manufacturer about the allowable tolerance.

I should tell you that I've never measured a hub, but I've measured lots of other things. Good luck.
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