Crankshaft Runout Test

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Vintage Engine Repairs
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Aug 12, 2019
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Thanks gents, some good points raised.

I’mm looking for a crank runout jig / v blocks for future builds, but nothing affordable here in Oz.

I decided to test it because I saw a random video suggestion on YouTube and thought I’d test it out on a chainsaw of mine.

They all had theirs off of their engines though.
 
stihl86

stihl86

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Thanks gents, some good points raised.

I’mm looking for a crank runout jig / v blocks for future builds, but nothing affordable here in Oz.

I decided to test it because I saw a random video suggestion on YouTube and thought I’d test it out on a chainsaw of mine.

They all had theirs off of their engines though.
Good v blocks aren’t affordable here either, lol
 
Woodslasher

Woodslasher

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Good v blocks aren’t affordable here either, lol
I found a pair of what appeared to be unused Starrett v-blocks in a pile of scrap in the weeds behind a guy's shop and gave 'em to a machinist buddy. All they needed was a little wire brushing and they would've looked brand new. It's amazing what you can find in the most unusual places.
 
Vintage Engine Repairs
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0.1 mm is 4 thou I would say it’s fine. Are you having problems with it?
No no, no problems. I literally thought I’d try it out because I had no idea what it would be.

The bearings are 20 years old but in good shape, that probably doesn’t help. I should try another saw, but as others have said, better to buy v-blocks and test it - I have an 045 I. Doing a full rebuild on so that would be good to test for interests sake.
 
pioneerguy600

pioneerguy600

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Im not surprised the bearings are why it was out a bit they gave you a false reading. The blocks saved you some money there.
The crank supported that far in from the ends will not give you an accurate runout reading, what you are checking at that point is precision of roundness. To test a crank for runout it needs to be supported on centers, each end of the crank is indented with a centering pilot hole. Then two dial gauges are used,one either side of the counterweights.
 
Vintage Engine Repairs
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Aug 12, 2019
Messages
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Location
Australia
The crank supported that far in from the ends will not give you an accurate runout reading, what you are checking at that point is precision of roundness. To test a crank for runout it needs to be supported on centers, each end of the crank is indented with a centering pilot hole. Then two dial gauges are used,one either side of the counterweights.
Thanks Jerry, I’ll do some googling to see what jig is available, though I guess a machinists lathe is what’s really necessary because they will be the only thing that’s truly accurate?
 
lone wolf
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Thanks Jerry, I’ll do some googling to see what jig is available, though I guess a machinists lathe is what’s really necessary because they will be the only thing that’s truly accurate?
A large C clamp with points from a steering wheel puller set installed then clamp the C clamp in a vice.
 
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