While there certainly are a few true "craftsman/artisans" out there worth every penny while building amazing saws, nothing to do with a single cylinder two stroke on soft metal cases is rocket science. I'm just a hobby type as many who visit places like this. I do bearings for my saws and for my very small set of customers. ( Can't/Won't take on any more than I have ) Even so, seems like splitting cases and replacing bearings & seals is a weekly event any more.
It's a mix of heat differential and pressure. Less heat difference between bearings and cases means more pressure or trauma to put those bearings in. Or More heat difference is less pressure. Of course the "upper" limit on the heat has to do with the materials exposed to the heat. Simple as that. How you get that mix is dependent on the tools at your disposal. Did a video years ago using a wood stove, made fun of the "red neck" approach or extreme field conditions but made the point it's about physics.....many ways to skin this cat.
I use one of three things...a turkey roaster, a hot plate, or a heat gun. Key to for me is nylon vs steel, stuff still on the cases or bare cases, is it my hobby saw or customer saw, it's the mix of those factors defines approach and temperature 4 me.....SO beginning of this first video, or end of the second covers the "least traumatic approach" assuming bare cases and a higher temp.
I guess the only caveat for me is when installing nylon caged vs. steel cages. Not really "scientific" and I'm not even certain is matters, just what I do. But when installing the nylon's; I chill the nylon caged bearings and keep the case temps in the 275 plus a bit but under 300, then chill the assembly really quickly after installation where as with the steels, I leave the bearings room temp and heat the cases to somewhere in the 300 plus range. Temps don't bother them as much and having less "tapping" or pressure with the higher temps as shown in these video's is less stressful on everything involved. SO showed lower temps with a heat gun with a little tapping. Not optimal but not enough to hurt anything either, do this if all the chain brake stuff is still on, a quick and dirty approach. And also show the higher temps with steel caged where you literally can drop them in.
Done some derivative of this set of approaches since the 1970's with motorcycle cases as well, pretty much anything with a press fit or interference fit bearing in Aluminum or Magnesium.
For those who need visualization, While these video's are really about 372's and the many versions, they also covers replacing bearings. The first minute or so in the first video...then just ignore the rest and jump to minute 20 the second one and ignore the rest.
jump to minute 20 on this video
