RaisedByWolves
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These should have been normalized prior to grinding which would rule out warpage.
Smart thinking though.
.
Blue bearings
- Thread starter clintb
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These should have been normalized prior to grinding which would rule out warpage.
Smart thinking though.
.
Steel Heat Treatment Basics
Steel is hardended by raising its temperature to its non magnetic state which is around 1500 F> It is quenched in oil, water or allowed to air cool depending on what type steel it is. After quenching most steels are too hard for use in most applications. In fact they are so hard they will shatter like glass if dropped or struck. The steel is tempered or reduced in hardness by heating it again.( around 400 F for high carbon alloys.) The higher the temper temperature the lower the eventual Rockwell hardness of the steel. If you raise it to non magnetic and allow it to air cool withour quenching carbon tool steel will be in its annealed state .( very soft.)
Bear in mind this is a very simplistic metallurgy explanation and some steel heat treatments are far more complicated. Some steel are air hardening and dont go through a rapid quench. Industrial heat treat ovens are computer controlled .The bottom line is that getting any tool steel or bearing steel too hot will ruin the heat treatment and can reduce its hardness considerably.
Did this happen to the bearing under discussion? Maybe , maybe not but I wouldnt take the chance on them.
Steel is hardended by raising its temperature to its non magnetic state which is around 1500 F> It is quenched in oil, water or allowed to air cool depending on what type steel it is. After quenching most steels are too hard for use in most applications. In fact they are so hard they will shatter like glass if dropped or struck. The steel is tempered or reduced in hardness by heating it again.( around 400 F for high carbon alloys.) The higher the temper temperature the lower the eventual Rockwell hardness of the steel. If you raise it to non magnetic and allow it to air cool withour quenching carbon tool steel will be in its annealed state .( very soft.)
Bear in mind this is a very simplistic metallurgy explanation and some steel heat treatments are far more complicated. Some steel are air hardening and dont go through a rapid quench. Industrial heat treat ovens are computer controlled .The bottom line is that getting any tool steel or bearing steel too hot will ruin the heat treatment and can reduce its hardness considerably.
Did this happen to the bearing under discussion? Maybe , maybe not but I wouldnt take the chance on them.
Sprig
Addicted to ArboristSite
This is interesting mon. Is it true that some bearing surfaces are actually just surface hardened? I seem to recall reading something about this but am brain-farted out. If this were true I could see random uncontrolled heat usage messin' things up, Andy?
ShoerFast
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R Shaffer3
Just as part of a hobie, I had started to do my own heat treat on 52100, intresting that my best guess at a 375 draw was about 60 rockwell, or also just the faintest straw yellow color (or just the slightest or pale color) ,,,,,,,, true blue would be up there in the mid 500's .
If I may ask, where could I find more information on heat treating 52100?
I might be in the ball park, but I know I can get more out of 52100 then I am.
Al Smith
Addicted to ArboristSite
I would imagine you didn't do a thing to them unless they have plastic cages.
Usually you put the crankshaft in the deep freeze to shrink fit the bearing.
One method of heating the bearings is to immerse them in oil,then apply some heat.I saw this method employed aboard ship but have never used it myself.I usually just heat the inner race a tad with a big old American beauty soldering iron.It doesn't take much with a frozen cranksaft.
When you get the bearings on the crank,toss it back in the freezer for a spell.
After it's good and cold,heat the crankcase bearing pockets with a heat gun and install the crank,nothing to it.
Usually you put the crankshaft in the deep freeze to shrink fit the bearing.
One method of heating the bearings is to immerse them in oil,then apply some heat.I saw this method employed aboard ship but have never used it myself.I usually just heat the inner race a tad with a big old American beauty soldering iron.It doesn't take much with a frozen cranksaft.
When you get the bearings on the crank,toss it back in the freezer for a spell.
After it's good and cold,heat the crankcase bearing pockets with a heat gun and install the crank,nothing to it.
You changed the hardness of the bearings, They are now like they would be in a saw that was severly overheated use new ones. They are no longer the hardness they were ment to be which means they will wear prematurly. over the price of bearings I would not risk destroying a saw. Ps I'm a machinest but I'm responseble for maintainence on several machines in the plant I've seen bearings on our powdercoat oven go bad from 400degrees and they were only straw which comes before blue. Just my 2cents hope it helps.
timberwolf
Addicted to ArboristSite
The alloy makes a significant difference in the color changes.
One axe head I made up I preheated to 450f before welding, the idea was to reduce the chance of cracking the spring steel edge 5160 when welded to the unknown low carbon alloy body.
The high carbon steel turned only straw colored and the body blue despite being heated to the same temp.
Water quenching from 450f seamed to produce a reasonable edge, hard enough to keep the edge, but not brittle.
One axe head I made up I preheated to 450f before welding, the idea was to reduce the chance of cracking the spring steel edge 5160 when welded to the unknown low carbon alloy body.
The high carbon steel turned only straw colored and the body blue despite being heated to the same temp.
Water quenching from 450f seamed to produce a reasonable edge, hard enough to keep the edge, but not brittle.
Crofter
Addicted to ArboristSite
Bobc, I am with the scrap opinion. Even a too hot oil temperature in expanding a bearing for installation can reduce the hardness of 52100 bearing components. I seem to remember a figure of 385 F. as the lower threshold for bearing tempering but that does vary with the indivdual bearing spec.
One of the procedures with bringing a heat treat oven up before use is allowing it to stabilize. Localized temperatures in the oven can go much higher than the set temperature during the preheat so the oven setting is no indication of what temperatures those bearings might have seen. We only have the visual indication. Shoerfast is correct in pointing out that the preservative oils present on the bearing could be giving a false indication of temperature reached, but any blue colour on a bearing associated with heat, is a very bad omen.
The potential damage if the bearings do pile up just dont seem worth the risk. A spun bearing can ruin the crankcase or the crank or both!
One of the procedures with bringing a heat treat oven up before use is allowing it to stabilize. Localized temperatures in the oven can go much higher than the set temperature during the preheat so the oven setting is no indication of what temperatures those bearings might have seen. We only have the visual indication. Shoerfast is correct in pointing out that the preservative oils present on the bearing could be giving a false indication of temperature reached, but any blue colour on a bearing associated with heat, is a very bad omen.
The potential damage if the bearings do pile up just dont seem worth the risk. A spun bearing can ruin the crankcase or the crank or both!
ShoerFast
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Text book rule of thumb for an interfearance fit (bearing/shaft) is to heat bearings to 350 'max'* in oil, and cool the shaft in accatone/dry ice till it stops boiling. That gives you a 450 deg differance, if that dose not just fall togather, you have other problims, like a burr or things are mis-matched or not lining up. Just a swag, but its my bet that most bearings are treated to 60 rockwell or less (375 deg - maybe 450) to gain vibration/shock strenth?
* 52100 will take on the very slightest of color at 350deg. you need bright lights or sunlight and compaired to a non-heated bearing.
* 52100 will take on the very slightest of color at 350deg. you need bright lights or sunlight and compaired to a non-heated bearing.
Crofter
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Shoer, I know you are an old flintknapper! To get true temper colour indications requires you to remove all oil and surface oxidation to observe the run of tempering colours. As TW mentioned the old rule of thumb temper colours that apply to basic carbon steel are not accurate at all on some higher alloy steels. If an item is in a very hard condition as Shoer mentioned a temperature as low as 350 F can start to modify the hardness of some alloys. There is a series of high temperature bearings of an alloy closer to high speed steel that will stand much more heat than the tradidtional 52100 but they are not common.
litespeedrider
ArboristSite Lurker
Probably the coating turned blue, but not sure what it did to the metal at that temp. I used to put my black powder pistols in the oven at about 110 - 120 or so after washing with soap and water. Won't hurt them at that temp.
PES+
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That is what I was taught 100%
Also if they were only forgotten a few minutes at 450 oven temp set it is likely the coating oil burned.
If it was my personal saw I would give it a shot as I have done stranger things on clapped trash that I doubted would last long in a pinch and was surprised with the results
If it was for a customer I would use new to be absolutely sure
Also if they were only forgotten a few minutes at 450 oven temp set it is likely the coating oil burned.
If it was my personal saw I would give it a shot as I have done stranger things on clapped trash that I doubted would last long in a pinch and was surprised with the results
If it was for a customer I would use new to be absolutely sure
Al Smith
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This brings up an interesting question.Just how much difference in size is the inner race of the bearing to the shaft? I would guess no more than a couple of tenths,if that but I never measured myself.
The rule of thumb for a shrink fit was around a thou per inch of shaft/cylinder size if I remember correctly.I do know for example that installing a starter ring gear on a flywheel doesn't really take a whole bunch of heat.I doubt very much that on a saw crankshaft and mains that the temperature variation is much more than a couple of hundred degrees.
From my limited experiance a little stay in the deep freeze and a tap on a wooden block will pop off most mains from the shaft.I hear all this frustration of not having the correct pullers etc and I've never had a problem.Either I'm doing some thing right or I'm darned lucky.
The rule of thumb for a shrink fit was around a thou per inch of shaft/cylinder size if I remember correctly.I do know for example that installing a starter ring gear on a flywheel doesn't really take a whole bunch of heat.I doubt very much that on a saw crankshaft and mains that the temperature variation is much more than a couple of hundred degrees.
From my limited experiance a little stay in the deep freeze and a tap on a wooden block will pop off most mains from the shaft.I hear all this frustration of not having the correct pullers etc and I've never had a problem.Either I'm doing some thing right or I'm darned lucky.
Lakeside53
Stihl Wrenching
You're just darned lucky.
I just suck them on at room temp - no problems. Getting them off can sometimes be one heck of a struggle... Heating the old bearing with a heat gun solves that somewhat... that's a few hundred degress - much more then the 35 or so a freezer buys you. Some of the stuck bearings show signs of chatter / gaulng on the crank, and I assume that's really why they are stuck.
If you realy like cold... for $35 I can get a quart of liquid nitrogen
I just suck them on at room temp - no problems. Getting them off can sometimes be one heck of a struggle... Heating the old bearing with a heat gun solves that somewhat... that's a few hundred degress - much more then the 35 or so a freezer buys you. Some of the stuck bearings show signs of chatter / gaulng on the crank, and I assume that's really why they are stuck.
If you realy like cold... for $35 I can get a quart of liquid nitrogen
Tzed250
Addicted to ArboristSite
There is a 5 ft. tall container of it at work next to my machine...
Pitt
ArboristSite Lurker
Why would anyone take the risk of trying these out? Bearings and races are very cheap when bought from a bearing maker or distributer apposed to buying them as parts to something in particular. Bearings are rated by roundness, Abec, and more complicated means. You can purchase far better then stock for any application from a number of distributer. get a good micrometer, spec it, and count how many bearings are in the cage. $15. I have replaced ceramic bearings that spin at insane speeds ( sometimes hard to get) for 1/8 of what the parts dealer wanted.
You could have ruined the hardness
Coked the small amount of lube in the bearing case.
Ruined the bearing seal if the cage has one
Melted the bearing separator if plastic or warped a tin one.
not worth the risk.
You could have ruined the hardness
Coked the small amount of lube in the bearing case.
Ruined the bearing seal if the cage has one
Melted the bearing separator if plastic or warped a tin one.
not worth the risk.
Last edited:
PES+
Addicted to ArboristSite
Because of the supllied data
A few minutes in a home oven even at 450 degrees can't do much to the steel if it was an hour or close yah
Saw bearings coke up all the time and he said that when he re oiled they seem fine
Unless I am reading your post incorrectly it appears that you are suggesting replacing the steel balls in the metal races that you think may have had their hardness spec compromised?
A few minutes in a home oven even at 450 degrees can't do much to the steel if it was an hour or close yah
Saw bearings coke up all the time and he said that when he re oiled they seem fine
Unless I am reading your post incorrectly it appears that you are suggesting replacing the steel balls in the metal races that you think may have had their hardness spec compromised?
Pitt
ArboristSite Lurker
Well I work with a tool maker. He is a machinist who sets up lots of different things that need bearings. Further, I worked at the local Roller hockey/ skateboard shop as a kid with same guy. from day one we always tried to save by finding "houses" that sell bearings to company's who produce things. Obviously Stihl is not making bearings, they have what I would guess are German bearings (some of the best) and they are sourced from some maker. When you buy a bearing in Xsize from a distributer, you are paying far less then when your refrigerator fan dies in your house and you need to purchase same said bearing as Maytag part #XXXXX.
Many times when we have been stuck, I have pulled a dirty or used bearing, Removed the seal from one side, removed the cage and balls, cleaned and relubed and then installed that bearing with the open side facing in, still leaving an effective shield. I am not familiar with the saw's bearings. Most bearings that are engine applicable are needle/rollers/pins etc.. If the saw's bearings look like a reg roller bearings, yes you can clean them and reuse them provided that the heat did not damage the hardness of the bearing, and that the cages are made of metal. Look here
Note how these have a dust shield the guy is removing.
Now notice that the shiny chrome is not in fact the bearings but a form fitting cage that keeps the balls separated. This cage is sometimes plastic and would be damaged by excessive heat. If it is in fact metal, it would need to be carefully lifted and removed to get access to the balls in the bearing. Once your cage is removed, you can soak the bearings in kerosene, or any solvent in hopes of removing any burnt oil, dirt etc.. Then you reverse the process and get yourself a nice cheap arbor press.(you guys like the name already)
. Between foreign cars, tools and toys, I have pressed on my share of bearings. IMO, there is more risk In heating a bearing then not. Heat the seat, leave the bearing at room temp, have the right size race to press and poof! they go on/inPitt
ArboristSite Lurker
Well I work with a tool maker. He is a machinist who sets up lots of different things that need bearings. Further, I worked at the local Roller hockey/ skateboard shop as a kid with same guy. from day one we always tried to save by finding "houses" that sell bearings to company's who produce things. Obviously Stihl is not making bearings, they have what I would guess are German bearings (some of the best) and they are sourced from some maker. When you buy a bearing in Xsize from a distributer, you are paying far less then when your refrigerator fan dies in your house and you need to purchase same said bearing as Maytag part #XXXXX.
Many times when we have been stuck, I have pulled a dirty or used bearing, Removed the seal from one side, removed the cage and balls, cleaned and relubed and then installed that bearing with the open side facing in, still leaving an effective shield. I am not familiar with the saw's bearings. Most bearings that are engine applicable are needle/rollers/pins etc.. If the saw's bearings look like a reg roller bearings, yes you can clean them and reuse them provided that the heat did not damage the hardness of the bearing, and that the cages are made of metal. Look
Note how these have a dust shield and a retainer.
Now notice that the shiny chrome is not in fact the bearings but a form fitting cage that keeps the balls separated. This cage is sometimes plastic and would be damaged by excessive heat. If it is in fact metal, it would need to be carefully lifted and removed to get access to the balls in the bearing. Once your cage is removed, you can soak the bearings in kerosene, or any solvent in hopes of removing any burnt oil, dirt etc.. Then you reverse the process and get yourself a nice cheap arbor press.(you guys like the name already)
. Between foreign cars, tools and toys, I have pressed on my share of bearings. IMO, there is more risk In heating a bearing then not. Heat the seat, leave the bearing at room temp, have the right size race to press and poof! they go on/in
PES+
Addicted to ArboristSite
I understand that and agree on the heating the case. I hardly ever heat a bearing and then only in oil if absolutely necessary .
I just wondered about the reasoning of thinking that the balls would be ruined but the races would be OK to accept a much harder (though much more precise) ball.
In this case the cages are metal (Husky 372) unless he sourced some after market or other supplier
If the cages were plastic I would junk them
I just wondered about the reasoning of thinking that the balls would be ruined but the races would be OK to accept a much harder (though much more precise) ball.
In this case the cages are metal (Husky 372) unless he sourced some after market or other supplier
If the cages were plastic I would junk them
