Installing crank bearings using heat

[pioneerguy600]

This will be my first bearing job on a saw. I was not sure how smooth it was going to go by putting bearing in the half's first and than the crank in the bearings. This way sounds a lot easier. I read a lot of posts on this subject and this sounds by far the easiest.

I find it much easier this way also, don`t like the idea of pulling the cold case halves together with bolts.
Pioneerguy600

 

[blsnelling]

Great post, Jerry. Any problem getting the bearing to fall into a PTO side case that has a steel insert, like some Stihls?

 

[pioneerguy600]

Good thread Jerry. I tried to rep but I'm out of mix.

Thanks , rep is good I guess but I pay little attention to it, I myself like to see informative posts on chainsaw related issues.
Pioneerguy600

 

[pioneerguy600]

Iv'e been using heat on bearings for over 25 years.
Not the ideal way for a novice but it is the best way
for me. Just got to be careful too much heat will kill
a bearing.


Lee

I agree, got to watch how much heat is used, 220 *F would be max.
Pioneerguy600

 

[pioneerguy600]

Thanks Jerry, great method.

Thanks, its worked very well for me on all saws I have worked over the years.
Pioneerguy600

 

[Cantdog]

Excellent info Jerry. It has been my experience that just popping something in the home freezer is not nearly cold enough to get the results you are getting with heat. If you want to use cold it's gotta be dry ice to get any usable amount of shrinkage. I also have been waiting for someone to address the fact that you should not beat new bearings onto a crankshaft without supporting the backside of the counterweight in some way which you covered with the angle iron and a little heat and little or no pounding if you do not have the factory bearing installation tools. Again excellent!!!!

 

[pioneerguy600]

Great post, Jerry. Any problem getting the bearing to fall into a PTO side case that has a steel insert, like some Stihls?

On the steel insert saws I just let the case heat for a few mins longer but keep the temp set to the same limits, cool the bearing to shop temp but not freeze it and the bearing will go in with just the weight I can exert from pushing down on it. Once in a while I needed to pull the cases together the last half inch or less with the case bolts but usually the cases will touch or nearly so before needing the case bolts to draw it up tight.
Pioneerguy600

 

[pioneerguy600]

Excellent info Jerry. It has been my experience that just popping something in the home freezer is not nearly cold enough to get the results you are getting with heat. If you want to use cold it's gotta be dry ice to get any usable amount of shrinkage. I also have been waiting for someone to address the fact that you should not beat new bearings onto a crankshaft without supporting the backside of the counterweight in some way which you covered with the angle iron and a little heat and little or no pounding if you do not have the factory bearing installation tools. Again excellent!!!!

Definitely no pounding on an unsupported crank, with the crank supported on the angleiron the most I have had to do was a light tap on the driver from a 4-6 oz ball peen hammer, they slide into place very easily in most circumstances. Always make sure the driver you use only contacts the inner race of the bearing, my drivers are made to just slide over the crank stub and only contact the inner race, this gives the driver some very close alignment and helps square the bearing to the shaft.
Pioneerguy600

 

[pioneerguy600]

I tried this method, in the freezer, did not care for it. What bothered me was the condensation on the crank, which turned to water. I just don't like the stuff getting watered during assembly.

Very good thread Jerry, I like the just heat idea better!!


Mike

There would be a little condensation created but if it was not left to sit that way for long it should not cause damage, start and run the saw up to temp as soon as its back together would clear the condensation out. If you actually seen the amount of condensation a chainsaw goes through in its running lifetime it would be really scary. Running saws in the cold and then letting them cool creates condensation every time they are run, storing them in an unheated building in temperate zones does this also.In short saws eat a lot of condensation in their life cycles, thank goodness for two stroke oil , it helps keep some of it at bay but water does displace oil eventually and we all know what happens when it does.
Pioneerguy600

 

[ironman_gq]

I use the heat and freeze method on axle gear sets to seat the bearings. I think most bearings are safe up to 350 degrees before you need to worry about killing them. I usually just heat em with the torch until I definately cant pick it up without the welding gloves and I freeze the shaft (makes a huge difference when the bearing has 2 inches to slide down a shaft) makes things fall into place a lot easier and no pounding needed

 

[AKDriveSprocket]

The bearing I have from the Stihl shop have plastic retainer to hold the bearings in place. Should I be concerned about the plastic melting at 200*. And how long should all these be in the oven,bearings and crank cases?

 

[ironman_gq]

I wouldn't worry about 200 melting the retainer. Most parts of the engine reach over 200 in the course of daily use so they should be able to handle it pretty easily.

 

[pioneerguy600]

The bearing I have from the Stihl shop have plastic retainer to hold the bearings in place. Should I be concerned about the plastic melting at 200*. And how long should all these be in the oven,bearings and crank cases?

No, it will easily withstand 220*F., the time does not really matter if the temp is constant but anywhere from 3-5 mins is all I leave parts in there to soak up heat.
Pioneerguy600

 

[Cantdog]

Definitely no pounding on an unsupported crank, with the crank supported on the angleiron the most I have had to do was a light tap on the driver from a 4-6 oz ball peen hammer, they slide into place very easily in most circumstances. Always make sure the driver you use only contacts the inner race of the bearing, my drivers are made to just slide over the crank stub and only contact the inner race, this gives the driver some very close alignment and helps square the bearing to the shaft.
Pioneerguy600

Yes "beating and pounding" was just an exaggerated description. My point was concerning your method of backing up the crankshaft and not using undo force on a unsupported offset shaft. Yours seemed like a very good method and simple. Did you use square cut pipe for your drivers or turn down special drivers for various crank shafts?

 

[pioneerguy600]

Yes "beating and pounding" was just an exaggerated description. My point was concerning your method of backing up the crankshaft and not using undo force on a unsupported offset shaft. Yours seemed like a very good method and simple. Did you use square cut pipe for your drivers or turn down special drivers for various crank shafts?

Don`t take me wrong, did not mean you would beat on a crank but some may take it as ok to whack the crank, I posted a pict last year I think it was of a crank that was busted in two at the throw when an individual thought that he could pop the flywheel by hitting on the end of the crank. He did not know that the the flywheel should be held up or pried up before striking the end of the crank, well he broke the crank and brought it to me to see if I could weld it.
Most of my drivers are pieces of turned pipe, 1/2", 3/4", 1", 1 1/4"and 1 1/2"are id pipe drivers I have made and then there is some specialized drivers I have machined out, The 1/2" and 3/4" are the ones I use the most for chainsaw bearings, 3/4" -1 1/4" for most seals.
Pioneerguy600

 

[Cantdog]

HAHAHA!! I take it you didn't weld it!!! HAHA! Yes these made up cranks that rely on just an interference fit to stay in alignment seem like it would not take much abuse to either break or at least knock the two main shafts out of alignment with each other and the crankpin. Sometimes my humor doesn't make it all the way through the computer as the thought of pounding bearings onto a tiny saw crank I find humorous. But for sure someone could certainly not get my humor and cause themselves a lot of grief. Again as I said excellent thread and good info.

 

[pioneerguy600]

HAHAHA!! I take it you didn't weld it!!! HAHA! Yes these made up cranks that rely on just an interference fit to stay in alignment seem like it would not take much abuse to either break or at least knock the two main shafts out of alignment with each other and the crankpin. Sometimes my humor doesn't make it all the way through the computer as the thought of pounding bearings onto a tiny saw crank I find humorous. But for sure someone could certainly not get my humor and cause themselves a lot of grief. Again as I said excellent thread and good info.

No I ended up buying the saw, it was a quite nice MS440 and rebuilt it using a new crank, humour is quite hard to pick up from just reading words, or at least I have been told, many times. LOL.
Pioneerguy600

 

[HARRY BARKER]

why the pto side first?

 

[tdi-rick]

If I can add a little tip, if using a blow lamp, heat tip on an oxy, etc. to heat aluminium or mag to drop a bearing in, the best/easiest way to ascertain if the casting is hot enough is the water 'pop' test.
When heating occasionally splash a drop of water (or spit) onto the case/whatever you are heating and if it pops violently off the casting, stop, that's plenty hot enough. Your bearing will drop straight in. Anymore heat is too much.

 

[pioneerguy600]

why the pto side first?

I guess that I have done so many 044`s and MS440`s that it has just become a habit. With the 044`s I stripped an old oil pump and just install it on these saws when doing bearings, the bearing on that side goes in tight to the oil pump housing, it is used as a stop. I guess when I was thinking up how to word the thread last night that is the way I pictured it in my head. Either side could be done first.
Pioneerguy600