Blue bearings

[clintb]

Started rebuilding a 372, so i put the bearings in the oven. I forgot about them for a few minutes and they turned blue, they fell smooth after oiling. Are they still good?

 

[Dadatwins]

Why would you put the bearings in the oven, this would make them expand? I put mine in the freezer so the metal contracts and slightly heat the case they are going into. New bearing usually have an oil coat on them which is probably what turned blue. Did the color come off when they cooled down?

 

[04ultra]

Why would you put the bearings in the oven, this would make them expand? I put mine in the freezer so the metal contracts and slightly heat the case they are going into. New bearing usually have an oil coat on them which is probably what turned blue. Did the color come off when they cooled down?

Some guys heat the bearing and install them on the crank. Others install the bearing into the cases then ad the crank...


Clintb ....How hot was the oven??


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[timberwolf]

I would say if you got them up in the 450f or over you have just heat treated them perminently. I would not use them as the metal may now be brittle or soft depending on how long and how quickly they were cooled off.

 

[romeo]

I'm with Twolf

TRASHED

I have an 88 driver .404x.063 with about 10 seconds on it from one of the bikes. I forgot to turn the oiler on (expensive mistake) and its nice and blue now, still looks and feels right but I ain't gonna chance it. Order a set of bearings.

 

[clintb]

It's a gas oven, i set it about 450 to get it heating up and then was going to set it on 200 and leave a little while, but i forgot the last part. Is the bearings you get at an industrial supply the same as chainsaw bearings? It's a 6202/C3 VG 104, don't know what the last part means, the C3 means looser tolerance than standard. Don't want to have to order again, just got these today. Got another ebay 261 yesterday, $32 for saw and $25 for a new piston. Looks like a good complete saw, scoring on the exhaust side, low comp. I've read here that these saws had more power than a 036, that's hard to believe from such a small saw, guess i'll find out when the weather here cools off. Thanks for the help .

 

[Mad Professor]

+1 on the above two posts. Heating and cooling high carbon metal ( e.g. steel) effects its future properties. Bearings might be too hard, too soft , or just right ( sort of like a Goldie locks story.....).

PM me and I can tell you a story about tough, hard, and durable steel, that went through several heat treatments. My friend a master machinist built a couple knifes using ONLY the best materials.........took about 6 months (ordering steel etc....) but it is a damm nice carving device, it will CUT (very much tougher than) other knifes!

Why not spend an extra $20-30 and use new bearings? Some even said on another post to reuse GASKETS??????? WTF????? Seems there are bush leauge mechs that put POS together so they will run a week or two? I rebuilt two strokers for many years (addmitedly, not saws but MC bikes). The bikes that were "band aided" together ran, but not for very long.

My/your time pissing around on a down saw is worth more than that!

P.S. If not it is stihl a learning experience : )

 

[Tzed250]

Most likely AISI 52100, not good for it to be anywhere near the 400 deg. mark, as this is inside the tempering zone for that alloy. paperweights.

 

[TNMIKE]

Ditto the last post

I would toss the bearings and get new ones. You have ruined the temper in the steel by heating it. 52100 has a very precise heat treatment for a reason.

 

[rshaffer3]

I'm no metalurigst but I'm not sure if I agree with you guys. 450 deg f is nothing for steel. The transition temperatures are typically way higher than that and most heat treatments or tempers are done at over 1000 deg f, no? I don't think could have done much other than cook away the grease and any rubber seals.

I'll check with the metals engineer at my work tommorow to see what he thinks.

 

[jhellwig]

It's a gas oven, i set it about 450 to get it heating up and then was going to set it on 200 and leave a little while, but i forgot the last part. Is the bearings you get at an industrial supply the same as chainsaw bearings? It's a 6202/C3 VG 104, don't know what the last part means, the C3 means looser tolerance than standard. Don't want to have to order again, just got these today. Got another ebay 261 yesterday, $32 for saw and $25 for a new piston. Looks like a good complete saw, scoring on the exhaust side, low comp. I've read here that these saws had more power than a 036, that's hard to believe from such a small saw, guess i'll find out when the weather here cools off. Thanks for the help .

YOur oven isn't going to heat up any faster set at 450 than it is a 200....

 

[ShoerFast]

While agreeing with there 52100 steel, and that the heat treat would be effected at around 400 - 450 Deg.

My .02 cents worth is to use them,,,,,,,,,,, if the blue washes off, and there is nothing more then fainted effect of a straw yellow discolor to the bearings.

My reason is that there is a real good chance that a house oven did not draw a blue heat in it's temper, that there was a coating on the bearings that turned blue. Try washing them in a real good solvent?

A good hold time for 52100 is 2 hours after it came up to temp,,,,, and then it still will refine with repetitive heat treats.

 

[sawinredneck]

Well this is odd, normally my parts turn blue when it's too cold. Or when, well, I've been somewhere the wife didn't want me to be:hmm3grin2orange:

 

[PES+]

Or when, well, I've been somewhere the wife didn't want me to be:hmm3grin2orange:

It only takes two hours for those parts to turn blue?:help:

 

[Lakeside53]

One other thing... if they have plastic cages... another good reason to chuck them. Depending on the material, they may only be a rated to 150C.

And... the set point temperature of the oven may be much lower then the bearing - it's absorbing the radiant energy. Use a convection oven for more accurate heating or cover the bearing with a heat shield.

 

[clintb]

But, my little balls ain't blue, just the outside. Guess i'll ride to the bearing store and see what they know about the original bearing numbers.

 

[rshaffer3]

If the cages are phenolic the bearings are shot but here's some tempering data for 52100.

Tempering:
Assuming that the blade reached full hardness in the quench, tempering temperature of:
350 degrees F...............................60 - 61 Rc
450 degrees F...............................58 - 59 Rc
500 degrees F...............................56 - 57 Rc


57 Rockwell C is still really hard.

 

[Sprig]

I'm no metalurigst but I'm not sure if I agree with you guys. 450 deg f is nothing for steel. The transition temperatures are typically way higher than that and most heat treatments or tempers are done at over 1000 deg f, no? I don't think could have done much other than cook away the grease and any rubber seals.

I'll check with the metals engineer at my work tommorow to see what he thinks.

Neither am I and just going through this thread but this comes to mind, your saw bearings would never be reaching those sort of temps or you'd be doing some major melting somewhere, just makes sense to me. Blue'd? = Screwed!
No way anymore to tell what the temper is, you could have something that will shatter, something that will just fold into nice blobs, or it may have tempered just right, is it worth taking a chance? I think not, as others have wisely stated the same thing (hey I'm just reiterating, and my spellin's getting worse as da evening wears on :help. I am curious about what you were trying to do in the first place as others have asked so far (sorry if you answered this in later posts, I'll try to come back and do an edit), fitting on the crank? Hm, maybe yes then I think just a gentle heat from a heat gun or somethin' around 250- would have been sufficed, or maybe put the crank in the freezer for half an hour (near same diff no?). dunno but am intrigued as generally anything like this I've done the tolerences are close enough to only require some gentle tapping to seat things where they need to be. as I am in learning mode I will stop my blather and read further. I apologise for any headaches that ensue due to reading this post



Serge (formally know as 'Scourage O' the 49th')......... Its the stupid 'Prince' thing again rearin' its ugly head *shame* :monkey:

 

[sawinredneck]

I also wonder, if it does heat treat at temps that low, how much distortion was caused by that? I think back on my moldbuilding days, depending on the material, we allowed at least .010" per side for warpage and expansion during the heat treating proccess, then ground to a finished dimension.

 

[RaisedByWolves]

Sprigs avitar just disappeared right before my eyes........




Are the bearings junk? Maybe, go buy new ones.



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