# Crank shaft runout allowance ?



## Naiveambition (Apr 12, 2019)

whats an acceptable runout for a crankshaft.   I'm up to about .003 runout  and wandering what others are getting.. I know zero is prime and I do plan on making collet adapters for the flywheels to control wobble there. So what's the ballpark u all are getting or a good place to shoot for?


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## Brian Rupnow (Apr 12, 2019)

We all shoot for zero run-out. Damned few of us achieve it. As long as your flywheels don't visibly wobble, you're probably okay.---Brian


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## Bruce R. (Jan 23, 2020)

It’s tough to avoid crank runout, whether you machine from solid stock or build one up it seems there’s always something to mess with you. Soldering, brazing, and welding will do it, too much , or not enough center pressure on your tail stock center, heck, it seems like looking at it too hard will do it !   I make sure that my main bearings are dead in alignment, then I sacrifice 2 bushings by splitting them lengthwise. I put the bushings on the crank and install it in the frame, before I put the bearing caps on I’ll put piece of shim on top of the bushings. After the caps are tight the crank won’t turn, then I take my torch and heat up the crank rod throw till it’s glowing bright orange, and then let it cool slowly. I’ve cured a lot of runout this way.


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