Bearing fit on crankshaft

[mortalitool]

Im working on a saw and wanted to replace the crank bearings. the old ones slid right off so my thought was that the bearings were toast. New bearings came in and they slide right on the seats on the crankshaft. I assume this is not good and that the crankshaft is worn badly.

When I think about this something comes to mind....the speed at which the crankshaft rotates needs to be equal to the rate at which the inner race on the bearing must rotate, and if they are not equally spinning at the same speed this would create friction.

so am i correct in thinking the crankshaft is not usable?

I have done many bearing installs on saws and have only ran across this situation 1 other time. I replaced the bearings and the crankshaft and the situation was resolved.

 

[mortalitool]

@svk

 

[NWCoaster]

If you don't want to buy a new crankshaft and it is for personal use, you can use Loctite to hold the bearing in position. It's not how it was designed to be but works perfectly well. They make a green cylindrical locking formula or you could just use high strength red. Just make sure both surfaces are free of oil and keep it out of the balls/races. It will never come off unless you heat it to over 350 degrees.

 

[svk]

Funny I thought about telling him to do that but wasnt sure how the locktite would hold up to repeated heat and fuel mix. Glad to hear that it will.

 

[67L36Driver]

Only option.

Otherwise replace the crank.

Bearings need to be a light press fit on the shaft.

Shrink fit in the housing (outer race).

 

[bmwpowere36m3]

Only option.

Otherwise replace the crank.

Bearings need to be a light press fit on the shaft.

Shrink fit in the housing (outer race).

Not only... but likely the most economical. Permatex makes a high-temp sleeve retainer. They spec what clearance it'll fill. I think it was somewhere in the 0.008-0.013" range.

 

[mortalitool]

@svk want to try any of these ideas?

 

[67L36Driver]

The 'poor boy' way to make it tight is to prick punch the surface of the shaft. Many, many places.

The purpose is to upset enuff metal you get a press fit.

 

[bmwpowere36m3]

The 'poor boy' way to make it tight is to prick punch the surface of the shaft. Many, many places.

The purpose is to upset enuff metal you get a press fit.

Forgot about that... worked when I replaced wheel bearings in my dirt bike. First I tried high-strength thread locker, but it let loose within a few hundred miles (between loose and interference). On the hub (aluminum) I used a spring-loaded center punch to make a LOT of dimples AND I applied sleeve retainer. It has been holding since.

 

[Big_Wood]

If you don't want to buy a new crankshaft and it is for personal use, you can use Loctite to hold the bearing in position. It's not how it was designed to be but works perfectly well. They make a green cylindrical locking formula or you could just use high strength red. Just make sure both surfaces are free of oil and keep it out of the balls/races. It will never come off unless you heat it to over 350 degrees.

Red doesn't work. Don't even bother asking me how I know lol. The green retaining compounds made by loctite work great though. 620 has worked the best for me.