I need some outside-the-box ideas for platen wheels

P.Brewster

P.Brewster

Joined
Jul 25, 2007
Messages
1,380
Between my water spray, high belt speed, and high duty cycle, I get about a month of life from my 2" platen wheels. The bearings start dying, which causes the wheel to drag, which causes the wheel to wear unevenly, which causes the tracking to go bonkers, etc. (The stock TW-90 wheels lasted a long time but are not serviceable).

My ideas are below. Fire away with any fresh ideas or problems I might be overlooking. Obviously the common concept is that I need a way to easily swap out bearings. Thanks!

  • Use a stack of 2"OD/1"ID bearings as the wheel itself. This isn't really a solution if I have to press the bearings onto/off-of the shaft due to time/hassle required. I don't have a lot of experience with bearing press-fits so I'm not sure how much force will be required if I buy stock bearings and stock shaft material.
  • Get wheels custom-made that have a slip-fit bearing recess instead of the typical press-fit recess. This would allow me to pop out the bearings without any hassle and replace.
  • Since I have a significant water spray, maybe I can get away with some kind of bushing assembly or something that doesn't use balls, because heat build-up isn't an issue.
 
Could you use larger wheels to slow down the rpm of the bearing? Or get high quality bearings.

I am curious about the TW-90 wheels. Why can they not be serviced?
 
I don’t know a lot about bearings. Are these shielded bearings or sealed bearings?

I would also see what the local bearing supply store would recommend, they should be able to find a solution for you. I would try to use a larger sealed bearing designed for higher speeds. That would require a larger shaft and housing though.

Hoss
 
If you don't mind replacing bearings as they wear out, I'd just find a machinist to bore the bearing seats on a set of wheels to be a slip fit instead of press fit. That would only require removing a thou or two of material. Then you could just unbolt the wheels, pop out the bearings, pop in new ones, and be up and running in 2 minutes. (You'd still want to have a solid spacer between the inner races of the bearings to prevent crushing them when tightening down the wheel.)

Full ceramic bearings would solve the problem if your bearings are rusting, but wouldn't help if the issue is grinding dust ingress past the seals. That will kill a ceramic bearing just as easily as a steel one. And full ceramic bearings are very expensive. (Most ceramic bearings on the market are actually hybrid ceramic bearings with ceramic balls but steel races.)
 
Hubert S. said:
Could you use larger wheels to slow down the rpm of the bearing? Or get high quality bearings.

I am curious about the TW-90 wheels. Why can they not be serviced?
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Generally wheels can't be serviced because the bearing is pressed in, and can't easily be pressed out for replacement.

Yeah, larger wheels would help but I burn thru those quickly too. Whatever the solution is, it must be one that allows replacing the bearing while keeping the wheel.
 
DevinT said:
I don’t know a lot about bearings. Are these shielded bearings or sealed bearings?
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I've tried wheels from at least 5 of the popular grinder manufacturers, so the bearings are whatever you see on the popular grinders (I think shielded?).

Alpha Knife Supply said:
Have you tried ceramic bearings?
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No, so far I've only tried pre-assembled wheels with bearings from the popular grinder manufacturers. I'm willing to try any bearing, but a bearing is only useful if I have the means to install it into a wheel - and take it back out a month later when it fails.
 
CallumRD1 said:
If you don't mind replacing bearings as they wear out, I'd just find a machinist to bore the bearing seats on a set of wheels to be a slip fit instead of press fit. That would only require removing a thou or two of material. Then you could just unbolt the wheels, pop out the bearings, pop in new ones, and be up and running in 2 minutes. (You'd still want to have a solid spacer between the inner races of the bearings to prevent crushing them when tightening down the wheel.)

Full ceramic bearings would solve the problem if your bearings are rusting, but wouldn't help if the issue is grinding dust ingress past the seals. That will kill a ceramic bearing just as easily as a steel one. And full ceramic bearings are very expensive. (Most ceramic bearings on the market are actually hybrid ceramic bearings with ceramic balls but steel races.)
Click to expand...

Right, your first paragraph is exactly what I described under my second bullet point.

Regarding your second paragraph, yeah - I'm leaning toward cheap bearings that I can swap out more frequently. Thanks
 
Another thing to note, even a press fit bearing with a sleeve between the inner races is removable without damaging the wheel. The tool you need uses an expansion collet to grip the inner race of the bearing and then either presses on the outside of the wheel to pull the bearing or uses a slide hammer to pop it free. It's not very convenient, but it is possible.
 
Didn't people use skateboard wheels for this back in the day? I think they're about 2" and the bearings can't be too hard to change...
 
It must be worth figuring out how to remove the worn bearings.

I dont know how your wheels are assembled but I guess they are probably all very similar. I would try the following:

With a cheap arbour press (probably less than the price of a new wheel and always useful to have) or a hammer and metal bar or large bolt, press/hammer evenly on the center race of one bearing.

This will destroy this bearing and drive out the lower bearing (complete if you are lucky, just the center if you are not) and the spacer. Removing the seal and smashing out some balls first might make this easier.

Then it is a matter of tapping gently round the inside edge of the bearing outer races (use a piece of aluminium so as not to damage the wheel) until they come free. If there is no edge to tap on, then the manufacturer really did not want you to service your rollers and I wouldn't buy from them again!

Clean it all up, a smear of grease to make it easier next time and press the new bearings in with your arbour press and a suitable washer/round object so that you are pressing on the outer race.

It might take a while the first time but once you have it all set up it will be easy.
 
It is also worth gently removing the outer bearing seals every now and again and slapping some good quality water proof grease into the bearing. If you removed the seal carefully enough, it will just pop back into place.
 
If you machined the bearings deeper, you could put a seal like they use on motorcycle wheels to keep crud out of the bearings. The seals are dirt cheap, a couple bucks each for common sizes.
 
If your bearings are sealed, that is there is a black rubber seal between each race and not a metal shield or just open, get a 18 gauge 3 ml syringe and fill with grease. Use that to inject grease in between the races on some kind of hourly schedule.
 
12345678910 said:
Let's see a photo of your wheels and bearings and how you mount them.
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Right now I'm coming to the end-of-life of some standard Beaumont KMG 2" aluminum wheels, mounted via thru bolt, same way a normal KMG is assembled. I'm willing to fabricate/outsource any kind of mounting and I'm planning to have a 1/2" or 1" post rather than the thru-bolt.
 
Mike Read said:
It must be worth figuring out how to remove the worn bearings.

It might take a while the first time but once you have it all set up it will be easy.
Click to expand...

I appreciate it, but I'm thinking long-term here. Once I do what you mention, I'll have to do it all over again a month later when the bearings fail. My goal is a 5-minute bearing changeout.
 
Be careful injecting grease into bearings. If you're running them at a reasonable fraction of the upper speed limit (which you probably are on a belt grinder) then overfilling them will result in them running too hot and burning up. Typical fill is about 50% and that's using a lighter bearing grease. Filling them with a heavy, sticky grease isn't advisable at these kind of speeds.
 
P.Brewster said:
Right now I'm coming to the end-of-life of some standard Beaumont KMG 2" aluminum wheels, mounted via thru bolt, same way a normal KMG is assembled. I'm willing to fabricate/outsource any kind of mounting and I'm planning to have a 1/2" or 1" post rather than the thru-bolt.
Click to expand...

The bolt tension is probably a problem
 
12345678910 said:
The bolt tension is probably a problem
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Right, I've considered that, which is the primary reason why I want to go to a post mount (e.g. shoulder bolt or something similar). On the other hand, I'm aware of this issue and I've been very careful to only go finger tight + 1/10 wrench turn - the bare minimum to keep them locked in place. Moreover, the KMG wheels have the interior spacer which is supposed to remedy this problem. The wheels are definitely free-spinning when I install them. I do appreciate the help.
 
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