Bearing loose on the crank? Anybody ever tried this trick?

[marti384]

I understand the need for an interference fit of the outer bearing races into the case, and end play is another subject, but I'm still not clear why the crank and inner race cannot be a slip fit. Especially since it actually is in several different saw designs I own.

On those saws I doubt there is any more clearance between the crank and inner race than there is between the balls and the races of the bearings, so I don't see how this clearance allows the crank to move and pound against the outer race, therefore damaging the bearing pockets. Now some of those saws are the Poulan design with rubber coated bearings, so that would damp out any vibration before damaging castings, but not all of them are made that way.

The only issue I can see still is the possibility of the crank spinning in the inner race, but I have not see any sign of this.

Some saws, like those with crank seals integrated into the bearing, require a press fit of the bearing on the crank as an air seal. I had a 385 with an air leak between the inner race and crank after the crank had spun inside the inner race. After a while of spinning, both the crank and the inner race get wore down, and the saw wouldn't pass a pressure or vac test.

 

[Chris-PA]

the most common mode of bearing failure that i have observed in my short sweet life is when the bearing starts to fail and the inner race slips and rotates on the shaft. it causes the shaft to wear and requires both bearing and shaft to be replaced. a pressed, interference fit postpones that failure mode.

So then it reduces damage to the crank once the bearing has failed? But the slip fit isn't really the cause of the failure.

Some saws, like those with crank seals integrated into the bearing, require a press fit of the bearing on the crank as an air seal. I had a 385 with an air leak between the inner race and crank after the crank had spun inside the inner race. After a while of spinning, both the crank and the inner race get wore down, and the saw wouldn't pass a pressure or vac test.

OK, I can see the need there.

 

[heyduke]

So then it reduces damage to the crank once the bearing has failed? But the slip fit isn't really the cause of the failure.

OK, I can see the need there.

not really, what causes the failure is deterioration of the bearing. when the difference in torque between the bearing and the shaft is too great the bearing slips on the shaft and/or whatever holds the outer race. the trick is to replace the bearing before that happens. that's accomplished by regular inspections and/or predictive maintenance. there are accoustic tools that will let you know when the bear is starting to fail so you can replace it before anything is damaged. a pressed fit just gives you more time.

 

[bang]

Main bearings is not a place you want to save a few pennies. There is some real junk coming out of China even some name brand counterfeit stuff. I suggest getting bearings from a reputable dealer/distributor. Ball bearings have an internal clearance rating so make sure you use the proper class (c2, c3, c4 etc).

 

[Huskybill]

Once knurled id use the cylinderical 620 loctite that takes up to .015” gaps.

I used 620 loctite on large taper shafts on the dynamometers using 4,000lb weights to simulate a load. The used tapered shaft was in rough shape. After fitting it the loctite help up.

 

[stihl86]

You can buy " Handrulic" knurling tools on a visit to my daughter in the US of A I purchased one from a big Tool Super market in Spokane around $35 IIRC about 5 years ago

Can you give more details on this tool? Brand etc etc. But most of all does it work?

I know its an ancient post.

 

[alexcagle]

Like this?

 

[rupedoggy]

Bill you are getting better this thread is only three years old

 

[Huskybill]

Bill you are getting better this thread is only three years old

Oh crap I did it again. Friday’s chuckle I been up all night.

 

[cuinrearview]

When I started reading it i thought maybe @alexcagle was following up.

 

[Huskybill]

When I started reading it i thought maybe @alexcagle was following up.

Oh no here comes the whooping......lol

 

[cuinrearview]

Oh no here comes the whooping......lol

Mike already got ya.

 

[stihl86]

View attachment 802031
Like this?

Thanks. Not what I expected. But thanks. Your expert opinion is always appreciated.

 

[stihl86]

View attachment 802031
Like this?

Thanks. Not what I expected. But thanks. Your expert opinion is always appreciated.