pendragon1998
Well-known member
I need to install some bearings in a motor end housing. Am I better off freezing them with a spray of canned air, using my freezer, or trying to source dry ice?
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an alternative browser.
You should upgrade or use an alternative browser.
Shrinking a bearing
- Thread starter pendragon1998
- Start date
warm the end housing and freeze the bearing in your freezer
txvwnut
Well-known member
What he said.^^^^
OP
pendragon1998
Well-known member
I was concerned warming the housing would soften the paint. There's some paint in the bearing holes that I need to remove first, too. Can I sand it out or will that wreck the tolerances?
Last edited:
I was concerned warming the housing would soften the paint.
just warm it , don't get it hot then . can't say what degrees warm vs hot is tho LOL
I was concerned warming the housing would soften the paint. There's some paint in the bearing holes that I need to remove first, too. Can I sand it out or will that wreck the tolerances?
I'd carefully scrape the paint and then use paint thinner on a rag to get the last of it. Depending on the application the tolerances can be pretty tight. You don't want to spin a bearing.
OccupantRJ
Well-known member
On every electric motor I remember ever working with, the bearings are a light press fit on the rotor and slip fit into the end bell.
rlitman
Well-known member
I warm bearings by leaving them on top of a lightbulb. You could use the same heat source for the cup. It's gentler than a heat gun, and less likely to damage paint.
Yeah, leave the bearing in the freezer for an hour or two.
Yeah, leave the bearing in the freezer for an hour or two.
disston
Well-known member
I ruined a bearing I was installing on the end of the crankshaft of my motorcycle by aiming the heat gun at it and then walking away. When I went back, had been busy doing stuff and forgot it for maybe 30 mins, the bearing had all turned an ugly brown and after I cooled it it felt like sand was in it when I spun it. I seem to remember it was a $30 bearing.
You're not supposed to paint the bearing recesses in the housing. I'd use chemicals. Any sanding will likely change the interference fit and you could get a spun bearing which will ruin all your efforts.
Actually there is a way to fix a ruined bearing recess but we'll save that info for when you need it.
You're not supposed to paint the bearing recesses in the housing. I'd use chemicals. Any sanding will likely change the interference fit and you could get a spun bearing which will ruin all your efforts.
Actually there is a way to fix a ruined bearing recess but we'll save that info for when you need it.
theoldwizard1
Well-known member
just warm it , don't get it hot then . can't say what degrees warm vs hot is tho LOL
Really hot water warm !
OP
pendragon1998
Well-known member
You're not supposed to paint the bearing recesses in the housing. I'd use chemicals. Any sanding will likely change the interference fit and you could get a spun bearing which will ruin all your efforts.
Actually there is a way to fix a ruined bearing recess but we'll save that info for when you need it.
Yeah, I know. I was in a rush because I only had so long to paint before I had to quit that day, and i just clean forgot to mask the recesses. Stupid of me, but that's what a hurry gets you.
cvairwerks
Well-known member
We use dry ice and acetone most of the time at work.
Motor bearings are a slip fit to the end bells to accommodate assembly and thermal expansion of the rotor. 220 or similar sandpaper will work fine to remove the overspray by hand. A wire wheel on a die grinder will also work.
It is not possible to sand the bearing bore out of limits with 220 sandpaper unless you have several hours to spare and very strong fingers. I have sleeved many endbells and even in a lathe it takes a solid effort to remove a few tenths on diameter.
It is not possible to sand the bearing bore out of limits with 220 sandpaper unless you have several hours to spare and very strong fingers. I have sleeved many endbells and even in a lathe it takes a solid effort to remove a few tenths on diameter.
toolchaser
Well-known member
A&P Mech is, as usual, spot on. You can sand out the paint without fear. I had a customer bring me a track adjuster housing that he tried to hone out to fit a new piston, after 2 hours of honing, & maybe .0005" removed, he decided to bring it to me to bore on the lathe
Abeo
Well-known member
Just FYI, those air cans are flammable. The one I was using didn't say that, but the torch I was using to heat a motorcycle case did.
rlitman
Well-known member
Just FYI, those air cans are flammable. The one I was using didn't say that, but the torch I was using to heat a motorcycle case did.
Not all that much.
The oldest canned air products I've used contained R12. That's what used to be in air horns, for example. That hasn't been sold in years though.
Until recently, they contained R134a. That is not flammable at all.
Currently, they contain R152a. That is only half as fluorinated as R134a, so it is flammable, but from what I'm reading, only the liquid is easily ignited.
APEowner
Well-known member
Motor bearings are a slip fit to the end bells to accommodate assembly and thermal expansion of the rotor. 220 or similar sandpaper will work fine to remove the overspray by hand. A wire wheel on a die grinder will also work.
It is not possible to sand the bearing bore out of limits with 220 sandpaper unless you have several hours to spare and very strong fingers. I have sleeved many endbells and even in a lathe it takes a solid effort to remove a few tenths on diameter.
^^This^^. No need to complicate the project. Clean up the paint. Drive the bearings onto the shaft by driving on the inner races and assemble.
Dr Stan
Well-known member
One of the reasons I have an oven in my shop is to warm up bearings and bearing housings. Ditto on a small freezer in my dorm sized frig.
Keep in mind NEVER EVER put pressure on the seals/balls of a bearing. When installing on a shaft only place pressure on the inner race. When installing in a housing only put pressure on the outer race.
Of course this does not matter if the bearings are scrap and will be replaced.
As an aside. If you end up with just the outer race stuck in a housing, tack weld three spots roughly evenly spaced on the inside of the race. This will cause the race to warp & shrink making removal much easier. One can also quench the race for a more immediate effect.
Keep in mind NEVER EVER put pressure on the seals/balls of a bearing. When installing on a shaft only place pressure on the inner race. When installing in a housing only put pressure on the outer race.
Of course this does not matter if the bearings are scrap and will be replaced.
As an aside. If you end up with just the outer race stuck in a housing, tack weld three spots roughly evenly spaced on the inside of the race. This will cause the race to warp & shrink making removal much easier. One can also quench the race for a more immediate effect.
OP
pendragon1998
Well-known member
Motor bearings are a slip fit to the end bells to accommodate assembly and thermal expansion of the rotor. 220 or similar sandpaper will work fine to remove the overspray by hand. A wire wheel on a die grinder will also work.
It is not possible to sand the bearing bore out of limits with 220 sandpaper unless you have several hours to spare and very strong fingers. I have sleeved many endbells and even in a lathe it takes a solid effort to remove a few tenths on diameter.
Thanks - great info.
Shiftless
Well-known member
We use dry ice and acetone most of the time at work.
If you need to shrink metal parts, 108 degrees below zero will give you some room.
cvairwerks
Well-known member
If you need to shrink metal parts, 108 degrees below zero will give you some room.
On occasion, we get to install some replacement bushings that get soaked in liquid nitrogen for a half hour first.
PugetDude
ALLIANCE MEMBER
just warm it , don't get it hot then . can't say what degrees warm vs hot is tho LOL
warm<threshold of pain<hot
Abeo
Well-known member
Not all that much.
The oldest canned air products I've used contained R12. That's what used to be in air horns, for example. That hasn't been sold in years though.
Until recently, they contained R134a. That is not flammable at all.
Currently, they contain R152a. That is only half as fluorinated as R134a, so it is flammable, but from what I'm reading, only the liquid is easily ignited.
And the liquid is what I was using to freeze the bearings. The vapor cloud from the bearings sitting in the liquid ignited and made a 6 ft diameter flame on the floor.
This was in ~2011 with new air cans. Not trying to dispute you, just warning to others so they don't burn down their shop (I was lucky)