Newby question: OBM Grinder

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toobit

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Apr 13, 2020
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I purchased a new OBM 2x72 grinder from OBM. I noticed that with different sanding belts there is a light "thumping" when the belt goes around. My question is:

Is this normal?

How tight should the belt be?

How fast should the motor be going for what kind of sanding?

OBM does not have any information on these topics from what I have found. Any help/opinions would be great.

This is the grinder:
https://originblademaker.com/product/belt-grinder-2x72-complete-chassis-with-2hp-motor-vfd-combo/
 
sounds like belt bump. If so this is normal. Do some research on that topic and see if it sounds like what you are experiencing. Check the wheels for play and make sure the bearings are good. Maybe try to post a video.
 
Stang Bladeworks said:
sounds like belt bump. If so this is normal. Do some research on that topic and see if it sounds like what you are experiencing. Check the wheels for play and make sure the bearings are good. Maybe try to post a video.
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Ahhh "belt bump". I did notice where the belt is connected to itself it has a small red adhesive. I thought it may be that. There is only one belt that does this so far. I only have two belts though.
 
Probably the belts. Some belts are terrible, especially the higher grits, i learned quickly to spend my hard earned money on higher quality belts rather than going for the cheapest I could find. That said, some of the more expensive belts can be pretty bumpy and/or wobbly too. Its a game changer when ya get a pack of smooth running belts, my grinds turn out so much better.
 
deepobs said:
Probably the belts. Some belts are terrible, especially the higher grits, i learned quickly to spend my hard earned money on higher quality belts rather than going for the cheapest I could find. That said, some of the more expensive belts can be pretty bumpy and/or wobbly too. Its a game changer when ya get a pack of smooth running belts, my grinds turn out so much better.
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True that. I spoke to OBM and they said its def the belt. I need some good tutorials on speed of belt use. I will do the youtube.
 
I use a hand-held metal cutoff disc to rub off some of the grit over the taped joint. Softens the bump.
 
toobit said:
True that. I spoke to OBM and they said its def the belt. I need some good tutorials on speed of belt use. I will do the youtube.
Click to expand...

The ideal speed varies quite a bit based on belt grit, belt material, what you're grinding, your personal skill level. If you have a vfd, just experiment a bit and you'll learn the ideal combo of speed/belt grit and what you're trying to achieve. Worn belts will change everything, id recommend getting a nice assortment of various belts, various grits and weights. When I first bought a 2x72 I was surprised by how many factors are involved. There's a perfect belt for every job. And you're gonna get used to changing belts all the time. Never even considered all the variables of different belts when i was on my 1x30, but now, its more clear.
 
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deepobs said:
The ideal speed varies quite a bit based on belt grit, belt material, what you're grinding, your personal skill level. If you have a vfd, just experiment a bit and you'll learn the ideal combo of speed/belt grit and what you're trying to achieve. Worn belts will change everything, id recommend getting a nice assortment of various belts, various grits and weights. When I first bought a 2x72 I was surprised by how many factors are involved. There's a perfect belt for every job. And you're gonna get used to changing belts all the time. Never even considered all the variables of different belts when i was on my 1x30, but now, its more clear.
Click to expand...
Good to know.I just got it yesterday so I will see how it goes.
 
Welcome toobit. Check out the stickies and the forum's search function in the stickies at the top of the page. LOTS of info already out there and you won't have to wait for a response...
 
One thing to mention for the use of low number (36, 50, etc) grit Ceramic belts - fast as grinder will go with lots of pressure. You need at least 4,000 SFPM belt speed (belt SFPM roughly equals motor RPM with direct drive and a 4" drive wheel), and faster is better. Ceramics are best used for profiling and other use of high speed and heavy pressure. As your skill level increases you'll find high speed is also good for beveling.

As you move from those low grits to higher grits (120, 320, etc) you'll use lower speed with lighter pressure for finishing grinds.

For grinding wood and aluminum cheap AO belts are about the best, don't load up as quickly as ceramics with wood or aluminum.

Wood needs a sharp belt or it will "burn" easier.

Try Pop's knife supply for a good source of belts. https://popsknife.supplies/ (note there is no .com at end)
 
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