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How hot to heat a bearing for press fit?

Terry Keeley

Titanium
Joined
Oct 18, 2005
Location
Toronto, Canada eh!
I have a 6203 (17mm bore) ball bearing to heat up for a n6 press fit on a shaft (12-23 microns / 5-9 tenths).

I see the plates go to 400F or so but am not finding any info on "the Google".

The bearing has some sort of plastic cage...
 
In general, the recommended maximum temperature to heat a bearing for installation is 230 deg F. You don't want to go too low (wouldn't go below 215 F) or the bearing might stick during install.

I don't believe that the plastic cage changes things. But plastic cages are a very poor choice. If it would be for my use and important, I would not use a plastic cage.
 
This is about what I was taught nigh 50 years back

Bearing installation procedure - Turbomachinery MagazineTurbomachinery Magazine.

EG Bearings are limited in maximum temperature by the metallurgy of the rings as well as by use of any non-metallic components such as nylon cages or rubber seals. A good general rule of thumb is to heat bearings to a temperature 150 F greater than shaft temperature. This is sufficiently warm to allow the bearing to slide over the shaft while not hot enough to damage any components. In any case, do not heat open bearings above 250 F.

For bearings that have closures and are greased for life, 210 F is recommended as a maximum temperature so the 150 F difference over shaft temperature may have to be reduced somewhat for greased for life bearings. While ovens, hot plates and oil baths work, the simplest method to heat a bearing is with an induction heater.
 
A light bulb or cone type heater work too. I have a heat stick that melts at the proper temp but you need to watch it if you don't have a gage. Few bearings have plastic cages. the most common would be a polymide cage in a self aligning bearing which has largely replaced brass due to cost. Dave
 
52100 steel has a CTE of ~11 um/(m*C) or 6.6 uin/(in*F). Using this, your 17mm bearing diameter, and the max interference of 23um, the calculation of minimum increase in temp you need to generate a slip fit is as follows:

.023mm/(17mm * 11um/(m*C)) = 122*C (221°F) above shaft temperature (assuming the shaft has a similar coefficient of thermal expansion to the bearing).

Assuming you aren't chilling the shaft, heating the bearing to ~250F seems like a safe temp to get a free assembly, and will not affect most standard cage or race materials.

17mm is pretty small, if it were me I would lightly grease the shaft, have a press handy and heat the bearing to 200-250°F, then use the press to quickly send it home if the fit is tight. If you freeze the shaft, be mindful of condensation during assembly.
 
Use a bearing heater all the time for electric motors, the little bearings are a real pia...A 6203 just press it on not worth the trouble and you cant get hot enough anyway. Max temp of a c3 with seals is 250f and 225f would be the max for my shop...Phil
 
Thanks for all the help guys.

The bearing is actually a one-way clutch from GMN, they need that sort of press to work properly.

My shaft is +0.0007" over nominal so it sounds like 200F or so (greased + plastic cage) and chill the shaft. I don't have liquid nitrogen but will use some of that electronic cold spray, should bring it down some.

I'll have it lined up in a fixture then press it home quick. Instead of grease would a little "white lead" (center grease) be a good idea? Anything else to consider?

The bearing's a FKNN 6203 here: http://www.drivelineinc.com/files/products/fk-fkn-fknn-6200-series.pdf
 
I have a 6203 (17mm bore) ball bearing to heat up for a n6 press fit on a shaft (12-23 microns / 5-9 tenths).

I see the plates go to 400F or so but am not finding any info on "the Google".

The bearing has some sort of plastic cage...

"Plastic cage"/rubber seals used to be aprox. 90 Celsius. Anything else check with the manuf of that specific bearing. If you overheat it, it's toast.
 
52100 gets tempered at 150°c. apparently not much happens if reheating to 225°c, but i would not risk going that high. there are many more bearing steels.
 
Another bearing fitting ''trick'' I was taught as a lad.

You mustn't exceed 250F with around 220 being the optimum etc etc, ...........water boils at 212 F,(aka only 8 F difference and on the right side ;) ) so put the bearing in a thick polythene bag and boil the living daylights out of it.

FWIW Without temperature control oil is very easy to over heat !!!
 
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52100 gets tempered at 150°c. apparently not much happens if reheating to 225°c, but i would not risk going that high. there are many more bearing steels.

... and that's even without diving into "Made in India". :) Or in the Chinese "Germany" town/village/whatever.
 
theyr'e painful bits of prose, but when in doubt its all in the bearing co.'s material.....page 68 here

https://www.skf.com/binaries/pub12/...ce-handbook---10001_1-EN(1)_tcm_12-463040.pdf

Cheap and cheerful....hotplate with a bit 11 gauge on top. Set the bearing on it and watch the temp with one the laser temp guns


Do not heat open bearings to more than 120 °C (250 °F).

Do not heat sealed bearings above 80 °C
(175 °F) because of their grease fill and/or
seal material.

Great resource, thanks!
 








 
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