Wide Belt Sander Question/Problem

We have an older Jet 37" single belt wide belt sander. In general it performs ok but it's far better than not having it.

Occasionally I get chatter marks when using it that show up as lines roughly an 1/8" wide about 1/8-1/4" apart running across the width of the material. It is worse with glue ups than with standard flat stock. It appears worse when I try to put more than one piece through at a time.

Today I was sanding 2 glued up boards of red oak about 6" wide made from 6 - 1" rips. Sending one board through at a time it worked fine, send two boards at the same time and I get chatter mark and a noise that sounds like chattering.

Any ideas on what might be causing this?

Sanding belt seams? Harden rubber on older machine may may magnify the problem. Does your machine have a platen? Does it still chatter when you use the platen exclusively?

Hold down roller springs getting weak?

Belt tension slacking for some strange reason?

How true does the head run, and does it need to be dressed?

Bearings? (Though I would think chatter wouldn't be the only thing you'd hear)

Did your belt manufacturer change the splice adhesive so it's thicker than normal?



If it wasn't doing it before, and is now, something has changed.

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Originally Posted by Bill Orbine

Sanding belt seams? Harden rubber on older machine may may magnify the problem. Does your machine have a platen? Does it still chatter when you use the platen exclusively?

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I thought it was a bad seam on a belt but it did the same thing when I changed out belts. It does have a platen and it did not seem to matter if I had the platen down or up or anywhere in between.

The hold down rollers seem to be working fine and applying enough pressure. I do not think the board is moving so much as something in the machine.

I thought about belt tension but to be honest I do not know how to adjust it, I will look into that.

The head does seem to run true, it could likely be dressed but it is not really bad, there are two lines ground into the head roller but they are not in the areas I was running material and they do not seem to be a problem when I do feed material in that area.

I use Klingspor for all of our abrasives, I do think a seam weakened on one belt I tried yesterday but when I changed to a brand new belt it did the same thing.

The bearings are all relatively new so I do not think that is the issue.

This could very well be operator error or an adjustment I'm just not aware of needing to be made.

I, too , have a Wide Belt. When I got it, the seller cautioned me to monitor and promptly change the platen graphite. Said when it wore out, the sander would not maintain quality or accuracy.
Since I've not used it heavily, I have not need to repair it.
I would suggest you review your machine.

Thanks for the suggestion. The graphite and felt are both new.

Does this sander use air pressure?
What air pressure do you use and is the regulator working properly.
Is air pressure maintained to keep the belts tight?
Hope this helps.
Andy

Some good advice here. Do check if air pressure is proper and the belt is tensioning properly as others mentioned. I would lik to add another idea.... Is the sander head locked properly after belt change?

Could be planer marks that are only revealed with a lighter sanding, but sanded out with a heavier pass.

I thought the same but I tried running multiple passes while raising the table. Same affect. I need to check the specs on air pressure. I’m leaning towards belt sag and not enough tension. It’s thevonly thing that makes sense.

Quote:

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Originally Posted by Neil Gaskin

I thought the same but I tried running multiple passes while raising the table. Same affect. I need to check the specs on air pressure. I’m leaning towards belt sag and not enough tension. It’s thevonly thing that makes sense.

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The regulator may not being flowing enough? Pressure may be good, but cfm isn't high enough?