the tighter the belt, generally the better it is going to track.
BY FAR, the most common issue with belt wobble is the belt tension is not strong enough. You may need a stronger spring if you built the grinder. On the No Weld, when using a door spring, you have to double it over.
Always switch to a known good belt before you start tearing the heck out of your grinder. It may be the belt. When I get a wobbler, I automatically tighten and then check with a good belt.
Don't try another of the same batch/brand. Try a complete different brand as a grinder check.
Belts wobble way more on a flat platen than a contact wheel. Use wobbly ones on contact wheels or slack belts or just learn to grind with a little wobble. Your grinder should NOT wobble on every belt. If it does, it is the grinder.
If the belt on flat platen tracks fine at full speed until you put it to use, it isn't tight enough. Contact wheels same thing but it less obvious.
There are couple other things to know about belt wobble.
Cheap belts wobble WAY more often than better ones. In fact is is rare for a belt over $4 to wobble. If it does, it is usually just one with a bad glue job. Maybe 1 out of 200 better belts might wobble. The wobble rate on cheap belts is much higher.
You might try switching the direction they run.
If you get a wobbler, put in in the machine and leave it full tension. You want it to stretch and straighten out a little. If that doesn't work, so what. It didn't work before.
Mark wobbly belts and use them for something where a wobble doesn't matter.
Hope that helps..
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