Help with side wobble?

Patrice Lemée

Patrice Lemée

Joined
Aug 13, 2002
Messages
5,703
With the sander I am building, I have a side to side wobble in the belt. :( Any idea what could be the cause?

Any help would be greatly appreciated.

Pad
 
sounds like a its not taught enough, the only other thing i can think of is that a roller isnt right, maybey loose or crooked
 
Pad

Don't overlook the obvious, maybe you have a belt that is bad, have you tried another?

Jim A.
 
one other posibility is that the idler wheel needs more crown. I fixed an old crapman sander by putting a couple layers of electricle tape center of the idler wheel. Tracked much better after that.
 
Badkarma, the tension is ok, no problem there.

Jim, you got part of it right, the belt I was using to test was faulty. But there is still a little wobble. I will try a little more crowning like Will says. Thanks.

Another question: Is a little side to side motion acceptable, I mean like maybe 1/16 of an inch?

Pad
 
People pay extra for those special oscillating belt sanders.
If you are only doing basic stock removal,and it is only a very slight wobble,it will still work.If you want clean plunge lines,it will be a problem.One (or more) of the wheels is not exactly square to the others.This is the most common problem with wobbly belts.The drive wheel ,idler,and the contact wheel have to be in the same plane or the belt will try to track back and forth,rapidly (wobble).More crown on the idler wheel helps compensate for this,but the problem should be solved if you want the grinder to work right.If it is badly out of alignment it can cause the belts to break.Check the alignment, bearings, and shafts.
 
My first thought is that you have a wobbly belt(s). I hear this description all the time...

"side to side wobble about 1/8" "

Here are a few comments:

The belt manufactures don't pay a lot of attention to side wobble.... The majority of belt uses don't need true running edges. So, occasionally, a belt manufacturer will release a batch of belts that wobble more than others. Even premium belts. So you might try one then another and another and find that they all wobble a bit. And the more you pay attention to it, the more you'll see that nearly all belts have some degree of wobble.

I've also seen belts that don't have parallel edges...or that are not 2" wide every where...which makes them wobble.

Finally, belts are living breathing animals. They are sensitive to stress, temp and humidity. In damp humid conditions, they'll curl up. If they are left on the machine under tension, they will distort. So you might have been grinding nicely the night before last...and then this morning, notice that the belt is wobbling.


I know I sound like chicken little..in that there is no hope and we are all doomed with wobbly belts...But in a sense...that is what I'm saying. Sometimes they are better than others..but occasionally they will be terrible.


Here's the test: is it the belt or the machine?

Every time the belt makes one rev araound the machine, all of the other rollers make 6-8 turns. So if we have a wobbly roller we would expect the belt to wobble mulitiple times for each rev.

Put a mark on the belt...maybe a dot of paint for example. Then run the machine slowly and notice if the side to side wobble corresponds in frequency and amplitude with your paint dot. That is to say...the dot moves to the same side...the same amount everytime the belt goes around. If this is the case...it is the belt that is not true.

Yes, crowned rollers really help to make the belt stable.

I really don't mean to sound so negative...and I truly hope this helps a bit.

Sincerely,
Rob
 
rfrink said:
I really don't mean to sound so negative...and I truly hope this helps a bit.

Sincerely,
Rob
Click to expand...

Not at all, Rob. Your diagnosis of belt wobblitis is dead on. I happens.
 
Another possible problem not mentioned yet is do you release the belt tension after using it? On my grinder there is enough crown that it will dimple the belts if it stays under tension for period of time. Then when you go to use it there is a wobble until the belt gets warmed up and stretched back out.
So after I shut mine down I release the tension so the belt has a slight droop to it.

On the 36 and 60 grit belts it can take several minutes for them to stretch out and track correctly if they get dimpled.
 
I had that problem and tried everything to correct it and nothing seemed to work. Then one day I noticed my tongue was hanging out the side of my mouth. If I moved it left or right it would cause it to change. Dead center tongue placement will correct the wobble...... :D
 
Thanks for all your input. That should help me identify the problem. Hopefully I get a little time in the shop tomorrow. And the belts I have have been hanging in one place or another in the shop for the past year or so. I see now that this may have been a bad idea, maybe it has twisted them.

And for the wobbly wheel, well at least I know 2 of the 3 are ok cause they come from Rob. ;)

Thanks again for all your help.

Pad
 
Then one day I noticed my tongue was hanging out the side of my mouth. If I moved it left or right it would cause it to change. Dead center tongue placement will correct the wobble......
Click to expand...

:D :D Rolling on the floor laughin'...... (hee hee!) .....:D :D
 
if it's bad belts there is one way to make them usable. I haven't tried it, but Wayne Godard I think uses a carbide flat piece clamped to the side of his platten to straighten out the ocasional woobly belt. The belt edge runs against the carbide and it makes it run nearly true, true enough for rough grinding at least.
 
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