The Correct Way To Install Bearings

[Sidecarflip]

far as interference fit is concerned, keep in mind that the bearing also expands when the saw is operating. Not at the same rate as the case, but it expands as the case heats as well and why it has to be a larger than the case bore in the first place. I stick with the dimensional listing in the Machinery's handbook myself and I can actually obtain the dimensions of the bore, both cold and hot. I own a Mitytoyo as well as a Starrett digital CMM (Coordinate measuring machine as we use them in machining operations a lot). Not something a layperson can afford or need for that matter. I also own an optical comparator if that is of any consequence. All 3 are quite expensive as in over 15 grand for the 3.

 

[Sidecarflip]

I have the SKF master catalog in print as well. I get all my bearings from Detroit Ball. Have a commercial as in tax exempt account with them as well and the sell *** also. I shy away from China bearings as a rule. Conversely, I only buy domestic made steel and I always check where it was made. In fact I rejected a load of steel a while ago from Contractors as the rectangular shaped sticks were marked 'made in Mexico'. I don't play that and never will. I pay more for domestic products but I'm all about domestic stuff, always have been and I always roll that cost into my estimates on jobs, anyway. Everything we do here is entirely predicated on a quote for machining and fabrication, always.

 

[Sidecarflip]

I will attempt to replace/repair anything on my saws apart from bearings, seals and splitting cases. I have tried on two saws, both times I failed to get a proper seal, failed pressure test with time / parts wasted. I've learned my limitation and now I have a friendly mechanic who does these aspects for me (while I watch). These types of repair take real skill to get everything seated properly and you probably only develop this from working regularly on a variety of saw brands.

Not much skill involved in properly seating any bearings actually, so long as you comprehend 'interference fit' and utilize that and fit ANY bearing using the proper method of insertion and that is, never apply force to anything but the OUTER RACE and do it with a proper diameter tool. That and insuring the seal don't drag over the crank shaft end if the crank is already installed and that part is fairly easy using heavy thickness blue painters tape to cover the end of the crank when inserting. No need for specialized collars when painters tape will do, just fine. Nothing about rebuilding a saw is rocket science except custom porting, something I don't do anyway. If I need more power, I buy a larger powerhead, not that I do because I have both an 075 as well as an 090 sitting on the shelf above my supplies in the shop. You cannot get any more power than an 090 powerhead that I know of and the 075 rates right up there as well.

 

[sean donato]

There are restrictions imposed by our new administration concerning the public possession of cryogenic gas now. I get mine from my air-gas compressor station but I have a commercial account with them. We now reside in a 'protect the public from themselves' society. Cryogenic substances now have additional controls on them, not like before and it is dangerous if not handled carefully. Just like the the large (over 125 cubic foot) bottles of compressed Oxygen and why I have my large bottles filled, my Oxygen bottle for my O/A torch is a 250 btw. In fact I have all my bottles filled as I own them all, outright. That includes all my 125 cubic foot 75/25 bottles, my 100% Argon bottles as well. They all have my company name painted on them and I have special tags that go on them to notify the compressor attendants not to exchange, but fill only. I have and own at the minimum, 2 bottles of each flavor on hand all the time, kept in an outside bottle rack. I use a lot of gas as a rule in the shop when we are in production and that is now.

I'm not certain what administration you're talking about. I can literally stop and get whatever dewar air gas has in stock on my way home. No commercial account needed. I, also, own all my own welding gas cylinders. Never exchanged one, just get them filled. My shielding gas cylinders are all #6 330cu ft, oxygen is #5 251cu ft and acetylene is #4. I have several smaller cylinders for gasses I seldomly use. never had an issue getting them filled, had several that required hydro testing at some point or another.
Not that any of this has anything to do with mounting bearings.

 

[Sidecarflip]

I'm not certain what administration you're talking about. I can literally stop and get whatever dewar air gas has in stock on my way home. No commercial account needed. I, also, own all my own welding gas cylinders. Never exchanged one, just get them filled. My shielding gas cylinders are all #6 330cu ft, oxygen is #5 251cu ft and acetylene is #4. I have several smaller cylinders for gasses I seldomly use. never had an issue getting them filled, had several that required hydro testing at some point or another.
Not that any of this has anything to do with mounting bearings.

That is correct and I won't go there on this thread anyway.

 

[ZeroJunk]

The temp would be 392F

I could run it up to 450 and put the case halves in there when I am making biscuits.

 

[nedsim]

... and fit ANY bearing using the proper method of insertion and that is, never apply force to anything but the OUTER RACE...

Exophysical had it right back in post #9,
"never transfer force through the rolling members, from one race to the other"

In other words, if you're pressing the bearing onto a shaft, push on the inner race; if pressing into a housing, push on the outer race.

That's the official line anyway, and should always be followed if the fit requires considerable force to seat the bearing, or if you're using a hydraulic press where you have no feel for the force. If you do have a good handle on the force required, and how that compares to the bearing's thrust capacity (in the direction the pressing force is applied), you can get away with pressing on the opposite race. You're more likely to get away with this with precision bearing assemblies where the fits are generally looser and more tightly controlled than on less accurate applications. Think machine tool spindles (my world) vs. mill machinery.

 

[nedsim]

One thing that is often overlooked or not even thought about with the fit of these bearings is that the case actually expands a fair bit when the engine is run , the case absorbs some of the heat and a bearing that was loose at the install at room temp will be even more loose when the engine is at operating temp,when run on long extended cuts such as bucking large diameter trunks or milling situations the cases get quite hot and the bearings being made mostly of steel do not expand as much as the mag or aluminum crankcase.
.

The coefficient of thermal expansion of aluminum and magnesium alloys is approximately twice that of steel. The difference is such that a 100F temp rise will reduce the interference on a 40mm OD bearing by about .001 inch. (Sorry for the mixed units.)

 

[muddy42]

Not much skill involved in properly seating any bearings actually, so long as you comprehend 'interference fit' and utilize that and fit ANY bearing using the proper method of insertion and that is, never apply force to anything but the OUTER RACE and do it with a proper diameter tool. That and insuring the seal don't drag over the crank shaft end if the crank is already installed and that part is fairly easy using heavy thickness blue painters tape to cover the end of the crank when inserting. No need for specialized collars when painters tape will do, just fine. Nothing about rebuilding a saw is rocket science except custom porting, something I don't do anyway. If I need more power, I buy a larger powerhead, not that I do because I have both an 075 as well as an 090 sitting on the shelf above my supplies in the shop. You cannot get any more power than an 090 powerhead that I know of and the 075 rates right up there as well.

Maybe I'll get there one day. As described I lost faith in my ability after failing on two saws, now a friend does these jobs for me.

I totally agree with regarding caution about mods to increase power beyond what the saw is designed to handle (crank case, crankshaft etc.). Just buy a a bigger saw. I have an 088, but I would love to try an 090 one day, they are pretty rare in the UK.

 

[Sidecarflip]

Maybe I'll get there one day. As described I lost faith in my ability after failing on two saws, now a friend does these jobs for me.

I totally agree with regarding caution about mods to increase power beyond what the saw is designed to handle (crank case, crankshaft etc.). Just buy a a bigger saw. I have an 088, but I would love to try an 090 one day, they are pretty rare in the UK.

I'm sure my wife will sell all my saws when I pass and I will before her. My cancer will eventually get me. I'm also sure she will sell all of them for pennies on the buck, so be patient and you can probably get a killer deal. Have an 075 as well as an 090. Bought them both new and I really never used them much and they sit on the shelf with no bar oil in them or fuel either. They do have the old style Stihl bars with the greaseable roller noses and the 90 has a 2 man bar on it. Both have 404 skip tooth OEM chains on them and both are pretty heavy even though the cases are Mag alloy. No plastic on either but the top shroud and both have the optional and rare heated handles, which IMO, is a nice option. Not sure if Stihl even offers it on new saws today, simply because I've divorced myself from Stihl, I buy Echo now.

 

[huskydave]

I would be interested. I would give them a good home.

 

[RedneckChainsawRepair]

Have an 075 as well as an 090. Bought them both new and I really never used them much and they sit on the shelf with no bar oil in them or fuel either. No plastic on either but the top shroud and both have the optional and rare heated handles, which IMO, is a nice option.

Would love to see the pics of the heated handle set ups on both of those stihl saws 075 090. Never came across either with heated handles.

So pics of these please so can save.

Some small cc I have had with heated handles. 2 different ways also.

 

[Sidecarflip]

Camera is broken and I don't post pictures as a rule anyway.

 

[huskydave]

very rare with the heated handles, you had to special order them from most saw shops.

 

[Sidecarflip]

I special ordered all 3 actually, the 75, the 90 and the 28. Bought all 3 from Northridgeville Stihl in Northridgeville, Ohio. Probably not there now. Used to date the owner's daughter. She was a hottie as most country gals are. Probably weighs 300 pounds mow (if she's even alive) and has a troop of kids too.

Saw a picture of my ex wife the other day. The years weren't kind to her either. She resembles a kidney bean with stubby legs.

 

[huskydave]

Love the big Stihls.

 

[bwalker]

I understand that, but bearings do spin in chainsaws occasionally.

I probably would not use oil unless the assembly manual said to, which I havent seen.
I also try to avoid using presses. Mostly because it is possible in machines you're changing bearings in often to wear out the bearing pockets. This probably is not an issue with a chainsaw.
What I have always done is heated up the cases gently and and then either left the bearings in a deep freeze over night or better yet dunked the bearings in liquid nitrogen. They most often drop right in doing this and you don't have to heat the cases up too much. 150 degrees F is plenty.

 

[ZeroJunk]

I probably would not use oil unless the assembly manual said to, which I havent seen.
I also try to avoid using presses. Mostly because it is possible in machines you're changing bearings in often to wear out the bearing pockets. This probably is not an issue with a chainsaw.
What I have always done is heated up the cases gently and and then either left the bearings in a deep freeze over night or better yet dunked the bearings in liquid nitrogen. They most often drop right in doing this and you don't have to heat the cases up too much. 150 degrees F is plenty.

Bearings are in the freezer. I can probably set the case halves out in the sun today and get them too hot to touch LOL

 

[chilipeppermaniac]

Not much skill involved in properly seating any bearings actually, so long as you comprehend 'interference fit' and utilize that and fit ANY bearing using the proper method of insertion and that is, never apply force to anything but the OUTER RACE and do it with a proper diameter tool. That and insuring the seal don't drag over the crank shaft end if the crank is already installed and that part is fairly easy using heavy thickness blue painters tape to cover the end of the crank when inserting. No need for specialized collars when painters tape will do, just fine. Nothing about rebuilding a saw is rocket science except custom porting, something I don't do anyway. If I need more power, I buy a larger powerhead, not that I do because I have both an 075 as well as an 090 sitting on the shelf above my supplies in the shop. You cannot get any more power than an 090 powerhead that I know of and the 075 rates right up there as well.

HEY Bro, I have 2 075's. The one that I bought most recently, I had running to test before buying ir. It was a bit hard to stafrt and didn't like to idle.
The other one was already deemed by me to be a project/ likely a complete tear down. Low compression, broken fins on flywheel, handle that was wonky etc. Also got an 051 in that deal. I look forward to getting the cases split, new bearings, seals, fuel lines,

 

[bwalker]

Bearings are in the freezer. I can probably set the case halves out in the sun today and get them too hot to touch LOL

The sun will work just fine.