Grinder wheel bearings

Kevin McGovern

Kevin McGovern

Joined
Jul 31, 2015
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3,118
What is the process for replacing wheel bearings on a belt grinder? I smoked the daylights out of my tracking wheel bearings.
 
This sounds like a good how to thread. I was asking about this in a thread about bearings a few weeks ago. I have no idea how they are installed but I know the bearing in the flange on my KMG is in need of replacement. That may be different than the ones in the wheels, I haven't really looked.

If I had to hazard a guess I would say it may require a bearing press to either get it in or out or possibly both.

In my limited experience, mostly from working with my pops helping him out some 20 or so years ago, we used a bearing press and various size steel tubes to press them out or in. I know you can heat the wheel to expand it and cool the bearing to shrink it a little but I have no idea how effective that is and you don't want to do that to a sealed bearing or you'll burn out the seals. It worked well when we sleeved motorcycle cylinders way back when. Other than my mom getting pissed because there was a motorcycle jug in her oven stinking up the kitchen :D

Do a WIP thread if you could, I think it would be helpful to many.

-Clint
 
I just run a punch into it and tap them out from the inside with a hammer. They sit against a ledge so you can't just press them straight through.
 
I use a punch made from an old wheel bolt and a removal die made from a piece of pipe. I ground the bolt head down until it was the same size as the bearing OD. Set the wheel on the piece of pipe, slip in the bolt/punch, and tap out the bearing by hitting the bolt with a hammer. The punch needs to sit on the bearing lip and the die needs to sit on the wheel's side and allow the bearing to come out.

If you want to make the perfect tool for the job, grind/turn a punch from round stock with a 2" section that goes inside the bearing and then has a wider area that seats on the lip. This will assure the bearing is driven straight out. The same tool can then be used to tap in the new bearing. If you go to the trouble of making a bearing punch, I would harden it and temper at 500F.
 
I'd personally use a blind bearing puller, but I own one and do lots of work one 4 wheeler engines that necessitate owning one, had I not a punch and hammer.
 
so just insert the punch at an angle from the opposite side and tap it out? I assume i should alternate sides of the bearing so it comes out somewhat straight? also, what lubrication is needed if any for bearing maintenance? The bearings that are currently in there stated "sealed" so I don't know if lubrication is even possible? They did not last as long as i thought they should. My grinder does about 3400 sfpm and i have about 8 knifes, including handles, on this set.
 
kdogmcg said:
so just insert the punch at an angle from the opposite side and tap it out? I assume i should alternate sides of the bearing so it comes out somewhat straight? also, what lubrication is needed if any for bearing maintenance? The bearings that are currently in there stated "sealed" so I don't know if lubrication is even possible? They did not last as long as i thought they should. My grinder does about 3400 sfpm and i have about 8 knifes, including handles, on this set.
Click to expand...

Typically you cant lubricate them and by the sounds of it, I would invest in a better set than you are removing. Under normal operating conditions, the service life of the grease in sealed bearings exceeds the service life of the bearing so that, with some exceptions, no provision is made for the relubrication of these bearings.
 
One more thing to add they failed shortly after I sprayed them with WD-40 clean dust out from them. I figured since they're sealed that shouldn't be an issue but I've been wrong before, maybe even more than once
 
kdogmcg said:
One more thing to add they failed shortly after I sprayed them with WD-40 clean dust out from them. I figured since they're sealed that shouldn't be an issue but I've been wrong before, maybe even more than once
Click to expand...

Compressed air is probably a better choice for getting the dust off of the bearings. If there's dust IN them, they're already done for.

The seals on a sealed bearing can come loose from time to time, especially if they're ran over their recommended speed and heat up too much, or if they're damaged when they're pressed into place, or if they're not pressed straight and end up binding.

Most tracking wheels you buy "off the shelf" now days use chinese bearings to save on cost/increase profit margins. Not that china doesn't make some decent bearings, but you do tend to notice a difference in the USA brands (SKF, Torrington, etc...)

As recommended above, the old bearings should punch out fairly easily. If need be, you can add a little heat to the wheel, but it shouldn't be necessary.
Take care not to press against or damage the seal on the new bearings when you press them in.
 
knife to a gunfight said:
Compressed air is probably a better choice for getting the dust off of the bearings. If there's dust IN them, they're already done for.
Click to expand...

^^ I was actually taught the opposite during machinist training -- keep the compressed air away from bearings, as it can force dusty air into bearing seals and just about anywhere it wouldn't usually get to.

Sealed bearings are lubricated with a grease that has about a 20 year shelf life (with significant variance, of course). If you use your machines a lot, you will need to do bearings more frequently than this, but you should get several years out of a new set.

Having replaced a ton of grinder and machine tool bearings, I can tell you that you will be surprised how much grinder dust gets into even the best double-sealed bearings over time -- a lot of the fine dust really does find its way in to anything.

Also, many grinder bearings are 'high speed' bearings -- rated for more than standard motor bearings (motor bearings are designed to run at 3500 RPM, but often not too much more). Check the RPM of your wheels and the RPM spec of the bearings you want to put in before buying replacements.

I usually buy SKF (usually much nicer than typical) bearings for my machines, since it's a pain to replace bearings and it's worth it to me to have the extra insurance of a good bearing in there for a few dollars more (they are more like $10 for a standard bearing instead of $3 for a cheap import). MSC and lots of other places sell them.

To remove bearings, I use a bearing (gear) puller. A bearing splitter is nice to have but often unnecessary. Internal bearings like what you describe can be removed with an internal bearing puller. A lot of people also like expanding concrete anchors to do this.

Nathan's method works fine, too, but BE CAREFUL not to let the (hardened steel) bearing race scrape the soft aluminum grinder wheel on its way out (try not to let the bearing get too crooked in the bearing pocket)-- if you scrape out this area, then you will have permanently wobbly wheels. Be careful of this when putting the new ones in, too.
 
Keep a 1" SWARF brush handy to knock the dust loose on the bearing and use shop vac to suck up the dust much better than spreading it around. Surprising how much doesn't get pulled in by dust collection system.
 
I get about 1000 hours of use out of the bearing in question. It would probably be much more, but I grind wet.

Don't spray sealed bearings with WD40 or blow them with air. Leave them alone. Do nothing. There is nothing you can do to "clean" them, all you can do is force trash beyond the seals.
 
So spray them, don't spray them, brush them, and do nothing to them.
I feel like I'm back in the military.:D
 
For the record, I'm not recommending blowing them off with 150psi air gun, or jamming the gun right up into the seal, but I don't see what harm "dusting" them off will do. I'm certainly not going to mask them off when I blow the rest of my grinder down periodically. ;)

Granted, leaving the dust caked on them probably won't make any difference either, as long as your not cramming it on.


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