Crankshaft truing & balance part dux

biknut

biknut

Well-Known Member
Last time I tried to true a crankshaft I had good results balancing, but I didn't have a real good way to measure the runout accurately.

I'm in need of a couple more cranks, so I'm having another go at it. This time around I've got better tools, and more experience to help me.

I'm unlizing this small wood lathe as a truing stand. I was able to buy a live center on eBay, that allows me to chuck a crankshaft up in order to get accurate measurements. I just turn the crank by hand, and check the runout with my harbor slave dial indicator.

Last time around, all I did was measure the runout, and keep buying new cranks till I finally got one that wasn't to far off. This time I'm going to try to make the crank true by adjusting it myself. Actually I've already been working on one for 3 days. I've finally got it to less than 0.001 runout

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Excellent work! Truing the crank certainly looks to be a much better option than trying to order one and hoping to find a good one. Who knows, you may be the man we all end up ordering trued cranks from!

Peace, James
 
i plan on chucking it in my lathe to check for runout,do you have any details for the actual truing?
i doubt i have the skills to balance,but truing i think i could manage.
 
tooljunkie said:
i plan on chucking it in my lathe to check for runout,do you have any details for the actual truing?
Click to expand...

So far what I know is when you get one shaft good, it messes up the other shaft. I think I'm going to need 2 dial indicators.
 
i came across some instruction for truing years ago,but its in one of my many repair manuals,i will start searching.
i recall specific places to strike in order to align crank.it was not very important to me at the time so i only skimmed over it.will be getting another dial guage too,as well as making a set of vee blocks and a couple jig blocks for my press.
 
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looks like you got that crank pretty close.should improve performance,no?
i would like to think it helps rpm's,vibrations and lessens bearing and seal wear.
good video,i see a couple other bb videos too.
 
I'm done with one crank, and working on another now. I can understand why the stock crankshafts aren't better. It takes a lot of time to get them better than 0.006". If the factory trues the crank, just that part alone would cost as much as the whole motor.
 
biknut said:
I'm done with one crank, and working on another now. I can understand why the stock crankshafts aren't better. It takes a lot of time to get them better than 0.006". If the factory trues the crank, just that part alone would cost as much as the whole motor.
Click to expand...

The ball bearings probably have 0.003- 0.005" play, so the factories probably feel it's not that important to get them better than that.
 
Biknut, you've made an excellent work. Respect!

At the moment I have reached 0.0055". I had started with 0.015..". It was a horror. The crankshaft is new. I built it out of a new engine. I want to finish my work with 0.0012", but probably my result will be worse.

Multipaul

PS: C3 means min 11µm and max. 25µm for a 6202 bearing (according to my old SKF catalog). That are maximal 0.001".
 
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