And the winner for "Dumbest Use of a Needle Bearing" goes to...

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ccfl
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And the winner for "Dumbest Use of a Needle Bearing" goes to...

Post by ccfl »

...SKIL*, for their lovely #3375 Belt/Disc sander combo machine!

This is the non-driven drum/axle assembly, the source of the horrible shrieking noise this thing's been making for quite a while.
fail_01.jpg
fail_02.jpg
That right there is just plain stupid. No seals anywhere; no way to lube it after assembly (probably wouldn't have helped anyhow); the shaft is NOT HARDENED, though it does seem to have some fancy space-age Teflon(tm) coating (hey guess what? it didn't work!). It honestly would have been better if there were no bearings in it at all, just a plain bore in the pot metal drum running on the non-hardened axle.

Thanks to the nifty low mass casting style I will have to bore out the center of the drum and press in plugs that can then be bored to hold a REAL SEALED ROLLER BEARING. I might even use four bearings because why not.




* They're so cheap they couldn't even afford the second 'L'.
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John Evans
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Re: And the winner for "Dumbest Use of a Needle Bearing" goes to...

Post by John Evans »

Just make a new pulley and use a pair of sealed ball bearings. Soft shaft then not a issue and quicker than making and fitting plugs.
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warmstrong1955
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Re: And the winner for "Dumbest Use of a Needle Bearing" goes to...

Post by warmstrong1955 »

I would also send your pictures, with details & questions to SKIL. And, if you build new like John says, pic's of those parts as well.
You may hear nothing from them....but if you don't let them know....they will never learn anything.
That's how I see it.

I forwarded info to Black & Decker some years ago. I sent a letter with pictures on a leaf blower-vac, and info on how long I had the beast and how much I used it before it self destructed. It was well past warranty, but it was only in it's second season. Still looked shiny & new.
They sent me a prepaid Am-Ex gift card, for more than what I paid for the blower, and apologized, and told me they had discontinued that model. Much more than I expected, and a total surprise.

Bill
Today's solutions are tomorrow's problems.
dirtcrasher1
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Re: And the winner for "Dumbest Use of a Needle Bearing" goes to...

Post by dirtcrasher1 »

Just put a 6061 (oil impregnated bronze bushing) I believe and run it on a piece of drill rod, A1 01 etc etc or make some out of Delrin (oil impregnated nylon). Unless there is a heck of a pull on that, I can't see why needle bearings were used.

If it does have a tougher job, flat pillow block bearings that lock with an eccentric locking collar will work and have a grease fitting; If room permits....
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wlw-19958
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Re: And the winner for "Dumbest Use of a Needle Bearing" goes to...

Post by wlw-19958 »

Hi There,

(Ahem) 6061 is an aluminum alloy. Did you mean
841 bronze "Oilite" bearing?

Good Luck!
-Blue Chips-
Webb
Magicniner
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Re: And the winner for "Dumbest Use of a Needle Bearing" goes to...

Post by Magicniner »

Delrin is DuPont's trade name for Acetal/Polyacetal/etc./etc. , it is not Oil Impregnated Nylon, that's "Oil Impregnated Nylon" or Oilon.

;-)
ccfl
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Re: And the winner for "Dumbest Use of a Needle Bearing" goes to...

Post by ccfl »

-I have Delrin stock - not a good choice here, speed is too high and heat would soften it. For low speed bushes it is amazing, though.
-Load is relatively low, the only force is applied by a tension spring to keep the belt from slipping. Load it down enough to over-stretch the tension spring and the belt will slip on the driven drum.
-I would prefer to make a whole new drum from scratch, but the part is ~2-3/8" OD, and I only have aluminum in that size, no steel. AL would probably be fine but I believe if something is worth fixing it's worth over-fixing by some large degree. Don't wanna buy a rather expensive piece of metal just for this. If I already had it, sure! The original pot metal drum is still in decent shape on the OD so it is wearing well enough to be serviceable for a good while yet.
-I have -2RS bearings the right size sitting right here in front of me. The original axle is 12mm, and simple to recreate - two circlip grooves and a D-flat on one end to key it into the bracket so it doesn't spin. I have 1/2" O1 and 1144 on hand, wear will not be an issue once real bearings are fitted so I will use the easier to machine 1144.
-Cause of failure of the original design(??) was debris plus hardened rollers running on non-hard axle. If they'd used sealed needle bearings and a hardened axle (or even just a sealed bearing of almost any size/type and the same non-hard axle), we would all be off doing something productive right now instead of reading this thread.

Given all that, the solution is to bore out the ends of the drum to hold aluminum plugs, bore plugs to accept 12x32x10 double sealed bearings, make new axle.

Or... I may locate the new bearings so they sit on the unworn section of the original axle. Functionally there will be no difference. Original axle is plenty strong enough it was just the wrong choice to serve as the inner race of a needle bearing. :wink:
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warmstrong1955
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Re: And the winner for "Dumbest Use of a Needle Bearing" goes to...

Post by warmstrong1955 »

I think any plain bearing is not a good choice. They are best suited to low RPM applications.
Lot of RPM, a lot of friction, will result in a lot of heat.
And....not sealed to boot?

Ball bearing(s), sealed needle bearing....better idea by far.

Bill
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10KPete
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Re: And the winner for "Dumbest Use of a Needle Bearing" goes to...

Post by 10KPete »

That's not a low mass casting.... it's low cost! As in least material. What a joke that thing is...

Pete
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warmstrong1955
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Re: And the winner for "Dumbest Use of a Needle Bearing" goes to...

Post by warmstrong1955 »

10KPete wrote:That's not a low mass casting.... it's low cost! As in least material. What a joke that thing is...

Pete
My little Enco 1" x 30" & 5" disc combo has a plastic upper wheel. Holding up fine....10 years old, at least, and has consumed dozens of belts.
It does have a real ball bearing in it though, and a sealed one. (6206-2RS per the parts list)
Material of the wheel....not a big deal.
Choice of bearing is.

:)
Bill
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SteveHGraham
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Re: And the winner for "Dumbest Use of a Needle Bearing" goes to...

Post by SteveHGraham »

What does the whole shaft look like? Is it simple enough so you can turn a replacement from real steel instead of teflon cheese?

Wondering if it would make sense to apply weld around the worn region and then turn it back down to original size. That way, you get to machine AND weld. I guess you would have to use a 4-jaw chuck to avoid eccentricity.

It's always great to be able to take a flawed piece of junk and make it what it should have been in the first place. By making an aluminum handle to replace the one on my $5 blow gun, I turned true crap into something that should last 20 years.
Every hard-fried egg began life sunny-side up.
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warmstrong1955
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Re: And the winner for "Dumbest Use of a Needle Bearing" goes to...

Post by warmstrong1955 »

SteveHGraham wrote:What does the whole shaft look like? Is it simple enough so you can turn a replacement from real steel instead of teflon cheese?
Is Teflon-Cheese similar to Horror Freight's proprietary Chrome-Moly-Peanut-Butter?
Might be Gouda stuff ;)

:)
Bill
Today's solutions are tomorrow's problems.
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