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Is this bearing safe to use?

HuskyVarnYay

HuskyVarnYay

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I got a little aggressive with the heat gun and heated the steel cage enough to discolor it (around 375 degrees). Would this be enough to possibly weaken the steel causing early failure? It is a brand new Nachi bearing.
 
weimedog

weimedog

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I got a little aggressive with the heat gun and heated the steel cage enough to discolor it (around 375 degrees). Would this be enough to possibly weaken the steel causing early failure? It is a brand new Nachi bearing.
375 isn't going to hurt it if it's a steel caged bearing, but to get to "blue", that's more than 375. Blue is bad. Often a little brown will happen if u cook the oil film used to reduce chances of rust for the shelf life on the bearings...clean it use two stroke oil to re-lube it and it's fine. My question is why was the heat gun focused on the bearing? Steel caged won't die from a 375 degree Fahrenheit exposure. Using a press on cold cases at the same temps as the bearings will have a little material deformation / removal on the cases bearing pocket, might take one or two times to matter if the installation is done carefully and the bearings aligned properly; but it's there. Why I moved to heat and did not finish developing my case assembly tools years back to squeeze in bearings as a press would do. Wasn't sure if folks would warm the cases a bit to say 220 degrees & cool bearings then squeeze them which is a better and acceptable approach, so scrapped those prototype tools. Saw it more on the saws like 576's and 562's but the physics of interference fit has been understood for decades ... why even back in the motorcycle days we used heat. With steel caged bearings I stay in the 300 - 325 range don't go past 340-345 degree's on mine, and with Stihl and now Husqvarna's nylon caged I don't go past 300 with chilled bearings & a little careful "persuasion" if required and then cool them fast after installation. I also have moved from a heat gun to a turkey roaster. Much more controlled and even heat. A hot plate works... heat gun & thermometer comb is used to show it can be done if one is careful on video's although in the future the Turkey roaster is all I will use for builds from scratch :)
 
Gaudaost

Gaudaost

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375 isn't going to hurt it if it's a steel caged bearing, but to get to "blue", that's more than 375. Blue is bad. Often a little brown will happen if u cook the oil film used to reduce chances of rust for the shelf life on the bearings...clean it use two stroke oil to re-lube it and it's fine. My question is why was the heat gun focused on the bearing? Steel caged won't die from a 375 degree Fahrenheit exposure. Using a press on cold cases at the same temps as the bearings will have a little material deformation / removal on the cases bearing pocket, might take one or two times to matter if the installation is done carefully and the bearings aligned properly; but it's there. Why I moved to heat and did not finish developing my case assembly tools years back to squeeze in bearings as a press would do. Wasn't sure if folks would warm the cases a bit to say 220 degrees & cool bearings then squeeze them which is a better and acceptable approach, so scrapped those prototype tools. Saw it more on the saws like 576's and 562's but the physics of interference fit has been understood for decades ... why even back in the motorcycle days we used heat. With steel caged bearings I stay in the 300 - 325 range don't go past 340-345 degree's on mine, and with Stihl and now Husqvarna's nylon caged I don't go past 300 with chilled bearings & a little careful "persuasion" if required and then cool them fast after installation. I also have moved from a heat gun to a turkey roaster. Much more controlled and even heat. A hot plate works... heat gun & thermometer comb is used to show it can be done if one is careful on video's although in the future the Turkey roaster is all I will use for builds from scratch :)
I found ovens would yellow the Stihl grey powder coat, apart from that I have always had the best success with them.
 
sean donato

sean donato

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When I worked heavy duty diesel we would use the heat and freeze method quite a bit, the machinists in particular. Normally an oven was involved, but if it was something in the field the rose bud with a neutral flame was used, along with freeze spray. Here at home I use a toaster oven, and the freezer. Most times there little if any force needed to seat the bearings, also for plastic cages bearings it seems a hot oil bath to heat them works well, if not a bit messy. Many ways to skin a cat if you will.
 
HuskyVarnYay

HuskyVarnYay

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My question is why was the heat gun focused on the bearing?
I was heating up the inner race of the bearing to install the crank. This is my first time reassembling a split case chainsaw, so please forgive my ignorance. After watching a some videos and reading a bit about it, I thought I had formulated a method that would work with the tools I have available. Here's what I did step by step.

1. Heat the outside of both case halves with heat gun and install bearings. This part went smooth and the bearings dropped right in with no issue.
2. Heat inner race of clutch side bearing and drop the crank in. This part also went smooth and the crank dropped right in and seated flush.
3. Heat inner race of flywheel side bearing and drop the crank (with other half of the case) in and seal it up.

#3 is where I ran into a lot of problems. I assumed that since the clutch side went in so smoothly, that the flywheel would be the same, but that wasn't the case. When I went to drop in the flywheel side it started to go but quickly got stuck. I applied a fair amount of force to it as well, but I ended up having to heat the outside of the case on the flywheel side and tap the crank/bearing out, then use my puller to get it back off the crank. I had plans to try this again using a press for more force, and equal application of it, but I haven't made it back to that point yet. Could this method have possibly worked had I put the crank and other case half in the freezer?

I decided to give it another try yesterday, but this time using the press. When I tried to reinstall the bearing into the flywheel side of the case using the same method as before, it started, but got stuck, so I tapped it out and tried to install it again, this time I decided to try that part with the press. I felt like I was having to apply too much force this way, so I decided to go back to the drawing board before I ended up breaking a case half or something. This is the part that really has me confused. Why would the bearings drop right in with 0 force during the first installation, but give me trouble on the 2nd go around? According to my chinaman laser thermometer the case half was right around the same temp as before.

To make matters worse, I decided to put a thin layer of Threebond on the mating surface of both case halves along with the gasket for some extra insurance. So I had to clean all that crap off, and make another gasket after my initial failed assembly. I don't know about you guys, but I really hate having to do that. lol

So now here I sit with an assembled clutch side case half, with the crank installed. Along with a flywheel side case half, and an overheated bearing, trying to figure out where I went wrong. I am open to any and all suggestions.
 
weimedog

weimedog

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I think u made it too complex. The shop tools to pull the cases together are like $40 bucks delivered from a variety of places. Use heat to set the bearings in the cases then go to the shop tools to pull the crank in the pto side, and then the case halves together. SO much easier on everything. AND if u waste a $200 set of cases trying to pinch a penny, maybe a lesson learned.
 
HuskyVarnYay

HuskyVarnYay

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I didn't realize that was you, I have watched quite a few of your videos in the past. Lots of good information. After seeing how easy it was to pull that case together with the crank tool I may just have to get one. Will it work for a wide range of saws? I am currently working on a Husky 55 and have a 268 lined up after that. If I can just get over this hump it should be smooth sailing. I have more experience in areas outside of case assembly, but this first one is giving me a headache.
 
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