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Belt Sander Bearing

03/17/2018 12:26 PM

My cheap bench belt sander has been getting sluggish, so I stripped it down.
The bearings are dry and gritty and it was full of dust.
One bearing seemed loose on the shaft, I can only assume the bearing got tight and

started to rotate on the shaft wearing it down. (see top pic for close up of the area of the shaft where the bearing was sitting. shown by red arrow)

The odd thing is the surface doesn't look like that's the case, it looks more rough cast (unlikely).
I think it unlikely that it would be designed for shaft to float loose in the bearing inner race, but you never know!
I may be ably to turn the shaft down and sleeve it, or turn a new shaft, or just pack it with shims after all it's not a precision piece of kit. If I clean and oil the bearings they will prob' just attract more dust.
Any useful ideas, suggestions or comments welcomed.
The real solution is to upgrade to a better industrial grade unit, but I don't have the space for a big one on a stand, and the little one serves me well.
Del

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Guru
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#1

Re: Belt Sander Bearing

03/17/2018 12:38 PM

You answered your own question; "cheap belt sander". Those tools made in China do not use precision bearings and are generally not high quality overall. A good set of bearings could cost more than the entire sander.

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#2
In reply to #1

Re: Belt Sander Bearing

03/17/2018 1:04 PM

Yes I realised that when I bought it, as it was only for occasional light use.
However I've found it a useful tool so it would be good to mend/improve it as I don't have room for a big industrial one.
Del

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#3

Re: Belt Sander Bearing

03/17/2018 1:21 PM

I would just replace the shaft....and get some dust-proof bearings....

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#4
In reply to #3

Re: Belt Sander Bearing

03/17/2018 1:24 PM

BTW I did buy it September 2012, so it's done pretty well .
https://bowyersdiary.blogspot.co.uk/2012/09/belt-sander.html
Del

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#5
In reply to #2

Re: Belt Sander Bearing

03/17/2018 1:26 PM

I am an amateur machinist and if it were my sander, I would buy new double sealed bearings (general grade) and turn a new shaft. The bearings used may not have a uniform inside diameter. Put some Loctite bearing retainer on the shaft.

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#6
In reply to #5

Re: Belt Sander Bearing

03/17/2018 1:34 PM

Yup, I'll look at that, but the big plastic drum may be molded onto the shaft ...
Mind I could always turn a wooden roller
It'll give me something to tinker with.
There are some good youtube vids where people have made wooden belt sanders, bandsaw and all sorts of kit!
Del

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#7

Re: Belt Sander Bearing

03/17/2018 2:24 PM

The bearing journal can be built up by welding or metal spray and then reground to the required diameter for a press fit for a new bearing. However unless you have access to the necessary equipment, the cost for this will exceed the cost for a new, cheep belt sander.

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#8

Re: Belt Sander Bearing

03/17/2018 6:38 PM

You might try a Speedi-sleeve or similar to repair the shaft, or get yourself some Loktite 660, it will pack up to about 0.5mm of shaft wear and has a sheer strength of around 3000psi. Make sure the bearing is accurately centred on the shaft before the compound sets.

None of these options are cheap for such a small and inexpensive machine so, as has been mentioned by others, it may well be a better option to purchase a new machine

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#9

Re: Belt Sander Bearing

03/18/2018 12:49 AM

My thought is bearing corrosion. Is it possible that the sander was used on days when the humidity was high ? As the bearing cooled, water vapor was drawn into the space between the bearing inner and the shaft journal. This combined with acids created by wood rosin from the sawdust and caused pitting .

Just a guess.

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#10

Re: Belt Sander Bearing

03/18/2018 5:24 AM

Ha! I've found the worn area of the 12mm section of the shaft is still a whisker bigger than the end of the shaft where the pulley fits (10mm) . So I've turned the shaft down to 10mm . I should then be able to push on a sleeve over the area where the bearing fits and turn that back down to 12mm.

Just about managed to fit it on my little lathe .
Meanwhile the bearing have been soaked white spirit and cleaned up, they feel ok, prob' just gummed up with sawdust and old grease. If the shaft repair works out I may buy some new bearings as they are relatively cheap. I may re build the sander, removing a lot of the extraneous crap and making a better dust extractor fitting and making belt changing easier.

PS. Supplementary question, I've been reading up on shielded bearings vs sealed. The shielded obviously didn't do a very good job, but they say sealed loose you a little torque as there is a rubbing seal... shouldn't think that would be significant tho'. The sealed are actually cheaper too! So are sealed ok for that sort of environment?
Great fun
Del

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#11
In reply to #10

Re: Belt Sander Bearing

03/18/2018 6:24 AM

You can also get non-contact sealed bearings as opposed to either shielded or contact sealed types, they provide better sealing than the shielded but obviously not as good as a contact seal.

For a high fine dust environment such as a sander I would go for the contact seal one if you can get it in your size requirement - make sure it's double sealed, as some bearings have a seal on one side only.

The very small loss of torque and speed capability should not be a concern for your application.

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#12
In reply to #11

Re: Belt Sander Bearing

03/18/2018 8:09 AM

Ta', cheers I'll go for the contact seal ones then (double sealed).
I've just finished sleeving the shaft and turning it down, it looks good.
Del

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#13

Re: Belt Sander Bearing

03/18/2018 8:45 AM

Pic of bushed shaft

New bearings ordered (I went for good quality rather than cheapest)
Del

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#14
In reply to #13

Re: Belt Sander Bearing

03/18/2018 11:30 AM

Looks good! I assume the bushing was a press fit. If not, some Loctite or epoxy between the shaft and bushing would be appropriate (before mounting the bearing).

If the fit to the new bearing is not tight, then use more Loctite or epoxy when mounting the bearing, and assemble the bearings into their housings before the second Loctite or epoxy cures, to guarantee correct alignment.

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#15

Re: Belt Sander Bearing

03/18/2018 10:24 PM

One easy way that I have done this repair is to copper braze the wear point and have it turned to spec. It is best to mount shaft so it can be turned maybe with a helper heat it full circumference keep turning there should be no distortion but if there is this can be easily brought back to straight with a good flat surface and tapping or pressing.

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#16
In reply to #10

Re: Belt Sander Bearing

03/19/2018 12:15 AM

Del, just out of curiosity, have you ever thought of building the better mousetrap ? Now that you're building the better sander.

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#17
In reply to #16

Re: Belt Sander Bearing

03/19/2018 3:52 AM

Nope... we have Emily Cat to catch mice
Del

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#18

Re: Belt Sander Bearing

03/19/2018 5:29 AM

Badly sealed, low cost bearings ???

You may be able to build up with a "liquid metal" or epoxy "metal in a tube"

ex Loctite and others...

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#19

Re: Belt Sander Bearing

03/19/2018 9:52 AM

Definitely, use a pre-greased bearing with double seals.

Depending on how loose the bearing is on the shaft, you may be able to use a tolerance ring to fit a new bearing. Tolerance rings are unique, spring-like products meant for cases like this. I've never actually used one, but this is what they are designed for. They make products for the bore of the bearing or the bore of the housing. There are two manufacturers that I am aware of.

Saint-Gobain's Rencol brand - https://www.bearings.saint-gobain.com/solution/rencol

USA Tolerance Rings - http://www.usatolerancerings.com/

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#20

Re: Belt Sander Bearing

03/19/2018 10:11 AM

J-B weld to fill in the area and turn or sand down to flush. add a new bearing and away you go..

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#21

Re: Belt Sander Bearing

03/19/2018 1:36 PM

Forget the ball or roller bearings - switch over to bronze-phosphor bearings. A little dust buildup acts as seals keeping add'l dust out. Just keep them well oiled. Some bronze-phosphor bearings have oil caps for periodically dripping in oil. Bronze-phosphor bearings won't gall & bog down like ball or roller bearing will as long as they're oiled. The problem is that you can not easily tell if a sealed ball or roller bearing is oiled or getting dry & you can't easily oil them. You can tell if the bronze-phosphor bearings need oil by the condition of the "dust seals" at the bearing/shaft junction. Moist looking = oiled; Dried out looking = needs oil.

Also if any particles somehow manage to get into bronze-phosphor bearings, they are just flung out into the "dust seal", whereas particles that manage to get into ball or roller bearings are trapped inside forever & ground into a fine grinding compound.

I built a 6" floor model belt sander over 40 yrs ago & never had a problem. Although the bearings are worn and loose it still sands just as good as it did when I built it. I always make sure they're oiled when I use it; most importantly so if I'm fixin' to use it & haven't used it in a long while. All 4 bearings originally had the oil caps but I modified the 2 bearings on the bottom. For the 2 on the bottom I removed the oil drip caps, plugged the holes, drilled new "oil holes" for the bearings and instead, inserted 1/4" copper tubing into the topside of the bottom bearings where I drilled. The other end of the 1/4" copper tubing runs up the sides of my sander so that I can drip in oil from the top of the sander. I can oil all 4 bearings standing up & don't have to bend down & count on squirting oil "up" into the bottom bearings.

For sake of full disclosure though I have to admit I've only used it occasionally in the last 10 yrs due to health reasons (my body is officially busted up & I'm limited to occassional little projects now.) But since it still runs strong but not often like it used to get used, replacing those bearings moved down on my "to-do" list to priority #283.

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#22
In reply to #21

Re: Belt Sander Bearing

03/19/2018 2:10 PM

Sounds like a cool project, but I've already got the job well underway see post #13
Del

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#23
In reply to #21

Re: Belt Sander Bearing

03/19/2018 2:21 PM

Some of the new plastic bearings are absolutely incredible, and since they don't require lubrication, dust won't stick to them like it does to oil and grease. They can also include enough conductivity to avoid static build-up.

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#24
In reply to #1

Re: Belt Sander Bearing

03/19/2018 8:24 PM

Agreed! Those cheap Chinese power tools are just that. Shafts made of cheap steel, poor quality bearings, etc. We have Harbor Freight Tools here and I don't like buying their power tools. I've wasted money buying a Skilsaw, jigsaw, cordless drill, etc.

The only power tool I've had luck with is their 4" grinder (noisy, but works) and their DA polisher. Their polisher is actually a pretty good tool for around $50.

Here's an interesting thought. The OP has spent some time "fooling around" with the repair of his belt sander. Time is money and as I've grown older, time is very valuable to me. I love tinkering with things, but lately I've said no to many repair jobs. I hate saying this, but many times it's easier to just replace the broken tool or better yet - to pay a little more to get a quality tool that's going to last.

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#25
In reply to #4

Re: Belt Sander Bearing

03/19/2018 8:30 PM

5 1/2 years of service from cheap belt sander is pretty good. You may want to consider replacing the entire unit with another cheap one the next time it breaks down. I'm assuming it was less than $100, so consider the time you've spent + the cost of the parts. And you don't know if the other parts inside the sander are worn (brushes, bushings, seals, etc).

Here's how I think of it. If you buy a new one and get another 5 1/2 years of service, then you're in good shape.

I hope this helps.

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#26
In reply to #15

Re: Belt Sander Bearing

03/19/2018 8:33 PM

I like your idea. Braze with metal vs using loctite and/or epoxy.

I know the new glues are pretty good, but you can't go wrong with metal. GA to you!

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#27
In reply to #23

Re: Belt Sander Bearing

03/19/2018 8:35 PM

Plastic bearings? What type of plastic? You're not talking about plastic bushings, right?

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#28
In reply to #14

Re: Belt Sander Bearing

03/19/2018 8:38 PM

Do you think the bushing will start to move when the shaft gets hot? If so, would it make sense to use Loctite or epoxy to hold it in place and if so, would it be able to withstand the heat?

I think one issue would be if the bushing starts to spin. Would you recommend a quick hit with a welder vs some sort of glue?

I'm not an expert on this and I'm just picking your brain. Thanks

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#29
In reply to #19

Re: Belt Sander Bearing

03/19/2018 8:40 PM

I've always wondered if these things existed. Thanks for sharing!

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#30

Re: Belt Sander Bearing

03/19/2018 8:46 PM

Out of curiosity, has anyone every taken apart a quality tool to see how it's made? I'm going to assume that the metal used to make the shaft is better quality, but what about the bearings? Is it a superior design (to keep the dust out), better seals, better bearing material or a combination of the above.

I pulled down info on a Bosch belt sander. Let me know what you guys think. Bosch Belt Sander parts list

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#31
In reply to #27

Re: Belt Sander Bearing

03/19/2018 11:15 PM

My sample set from Igus has 32 kinds of plastic from which to choose, each with a different set of characteristics. At least one is rated for use up to 482°F.

Most of my samples are indeed bushings, but they do have true ball bearings. If I recall correctly, one of the ball bearing types uses glass balls with (very hard) plastic races and ball separators. Zero lubrication required!

I suspect there are other companies making plastic bearings of high quality, but this is the one I'm familiar with...

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