Speed Wobble on Certain Belts ?

Normark

Normark

Joined
Nov 7, 1999
Messages
6,651
Hey Guys...

Anyone get a speed wobble of certain belts ??

When I put the knife to the platen, the knife starts to bounce, like a harmonic vibration of sorts..

Doesn't happen on all belts and I don't think it's the seam causing it..

Any Ideas ??

Thanks

Eric
O/ST
 
I get bump with higher grit belts.well with most actually,but more noticable with higher grits! i find yellow j-flexx belts are a bit smoother then x-weight are.but i think belt bump is pretty common with flat grinding.
 
some belts are simply made not completely straight when they cut the belt and they wobble from side to size. Even norton and some higher priced belts sometimes are just made with a wobble. I'm guessing belts weren't orignally made for knifegrinding so they don't have to run perfectly straight. Most of the time they do and others were just cut bad. I have used 40 grits that run awesome and then some in the same box that just have a wobble to them. Fact of life :( It is not the seam. I bet if you cut the belt in half and lay the entire edge on a completely flat surface, you'll notice gaps.
 
Hey Guys..

Bali..

Yaa it's not a bump, buy a harmonic vibration when you touch the blade to the platen,, it literally starts bouncing..

Leu..

Yaa thats what I'm thinking for sure...
I'm going to talk with the dealer about it..

Thanks

Eric
O/ST
 
i get a wobble on the 60 grit blaze from side to side. but the 220 grit are smooth as silk.
 
The other source of harmonic vibration can be the belt tensioner, just a little slack and it will begin harmonic vibration. I can get it to go away by tightening up a little bit on the spring tension.

George
 
Personally in my experience, it has nothing to do with what grit the belt is. Some are just cut crooked as far as the belt strip and that causes the wobble. Sometimes, the wobble goes away as you start to grind. Sometimes the belt wears away and trues itself. Most of the time it doesn't work that way! I find that truing seems to work when grinding on a higher grit belt than say on a 40 grit belt where the grit is so much larger. The tension on a machine for instance on a coote ....should just determine whether the belt stays center or rides to the left or right of center. :D
 
Eric

The wheels above and below your platen are adjustable on an eccentric. I suspect adjusting them so the belt contacts the platen more solidly may help your vibration

Rob!
 
Put a slight crown on your idler wheel . This will improve tracking and wobble . Also tighten your tensioner.I have also noticed belts wobble more with a harder contact wheel. Hope this helps.
 
If you lossen the bolt holding on the top or bottom wheel, you'll see the bearing shaft is eccentric to the bolt axis. Just turn the shaft a bit (fiddly) and retighten where you want it.

This setup is on every Bee I have ever seen.

Rob!
 
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