Is 2800/3450 RPm too fast for a contact wheel?

Tom Lewis

Tom Lewis

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Feb 24, 2000
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I have a Harbor Freight surface grinder that I would like to convert to a belt grinder. The motor on the surface grinder says the RPM is 2800/3450. Is that too fast for a 6" serrated contact wheel with a 90-100 durometer?

Thanks for any help.
 
I can't help on the "too fast?"

2800/3450 are probably the speeds on 50 Hz and 60 Hz mains respectively.

Your profile shows your location as Carlsbad, New Mexico, so you are presumably on 60 Hz mains. This should narrow things down to just one speed of 3450 RPM and, as Kuraki says, 5416 SFM.

My dimly-remembered and extremely limited experience of surface grinding with belts involved a VFD and speed seemed to make a big difference to the finish obtained. I do recall the sweet-spot was lower than I'd expected.
 
Tom
Norton recomends 3720 Surface feet per minute SFM for their Norax belts. So 5416 would be a tad fast.
Check Ebay or one of the surplus places like surpluscenter.com.
 
That does sound fast, but I wonder if the contact wheel would hold up at that speed. Lots of surface grinders have been converted to contact wheels and belts. I wonder if the speed is a problem with them.
 
Tom Lewis said:
That does sound fast, but I wonder if the contact wheel would hold up at that speed. Lots of surface grinders have been converted to contact wheels and belts. I wonder if the speed is a problem with them.
Click to expand...

I can t find on tube video where one man grind bevel on serrated contact wheel on 7400 SFM . . . .
Well , I found it ........7500 SFM , and was eye opener to me :)

 
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I have a couple of contact wheels marked for a maximum surface speed of 38 metres/sec. I make that 7480 SFM. They are probably 80 duro-ish, 10" and 14".

I'd not expect a problem with the wheels holding together at under half that SFM. However, during my one experience of surface grinding with belts, it was very clear that the drive/contact wheel "grew" as the speed increased. I think it was a 60 duro.
 
I'd have to check the tag when I'm at the shop, but I believe my 12" bader wheel is rated for over 3500 rpm. With a smaller wheel I wouldn't worry about that aspect of it at all.
 
You can run it at that speed. The wheel will be fine. Belts may give way faster. Getting slapped by a 36 grit belt running at 5400sfm is going to make you have to change your pants.
I would either change the drive system to one that allows step pulleys, or find a 3 phase motor and VFD. The VFD option is a far better one.
 
Thanks everyone for the information. Stacy I have been slapped by 36 grit belts before although not going that fast. That's one reason I still like my square wheel grinder.
 
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