pressing of ABEC9 bearings

[hector002]

I have been told that heating the bearing housing to make the pressing my precision bearing easier could change the structure of the metal and slightly change the allignment of my bore.

Any comments on this- i would be heating the housing up to around 150-200 deg F. I could see this being an issue if i was heating it red hot but should i be concerned even with lesser heating.

 

[NickE]

What is the housing made of?

Nick
I love materials science!

 

[dimjim]

Why not follow the manufacturer's guidance
as I assume this will effect the warrantee?
Can you cool the bearing instead?
How large is the bearing od or housing id?

 

[hector002]

sorry- i left out tons of info.

bearing OD is 3.543"(90mm), being pressed ~2" deep into a carbon steel housing bore ID 3.543" +0/-0.0003.

The bearings can be cooled to ~32 deg F but not much lower.

To clairify, I have two bearing housings, line bored to ensure as close to prefect concentricity between the bearing bores. Ideally I would like to created enough of a temp difference between the bearing and housing to just drop the bearings in and avoid any 'heavy' pressing. However someone warned me that heating up the steel housings and letting them cool could slightly shift the bore concentricity that I tried so hard to achieve.

What i think the person was refering to something similar to how they heat quench metals but i would only be heating to 150-200 deg so im not sure it this is still an issue.

 

[israelkk]

I think what he meant is that the heating will release some residual internal stresses inside the housing which may cause dimensional changes. The correct procedure was:

1. To machine the housing bore ID almost to the final machined dimension leaving minimum material to remove.

2.Heat the housing to the temperature you want to use to install the bearing and let the housing to stable. It may be even a better idea to use a little higher temperature.

3. Final machine the bore ID, the minimum material remove the best.

 

[hector002]

israelkk, that is probably what he ment- unfortunatelly the housing has already been machined- any suggestions as to a safe maximum temp i can get up to before removing these internal stresses?

 

[dimjim]

If the metal expansion rate
is .000 0065 per inch per degree,
then the temperature difference
need only be 13.1 degrees difference
for the .0003 change or expansion
of the 3.543 housing. So a much
lower temperature could be applied
without distortion of the housing.

 

[NickE]

Low alloy / Low carbon steel?

Id say that a heat gun wouldn't hurt your concentricity too bad. Maybe 150F, I would go slow and evenly. Can you use LN2 on the bearing? Or Dry-Ice? both are easily available in most cities and relatively in-expensive. Much cheaper than re-boring fer sure.