Buffer /Grinder question...

Well gents heres another nube question for all the vets...First , Am I correct in assuming that a buffer and a grinder are the same but with different wheels attached to serve an individual purpose?
Second, as I look for variable speed buffers I see nothing but buffers at or above 3450 rpm. The one Im looking at is a Delta variable speed Amazon.com: DELTA GR275 6-Inch Variable Speed Grinder with Tool-Less Change: Home Improvement
its lowest rpm is 2000.
In all the threads I have read on buffers , a lower rpm (1700-1750) is recommended for cleaning up razors. I have yet to come across one in my search. Can any of you shaed some light?
Thans in advance
-Ben

Yes, they are both electric motors with different attachments. Some "buffers" have longer stems coming out of the motor that gives you more clearance between the wheel & motor. Keep on searching and I'm sure you will find one in the lower rpm range...I think Sears has one of the variable grinders. Baldor, IIRC, is one of the major players in the buffer market. You could go to the "bay" and type in Baldor buffer & you will get a few hits. Caswell plating also offers some IIRC. Slower is better....

yeah, I checked with the sears one first thats 2000rpm at its lowest as well. Im going to look into the others now . Thanks

Harbor freight usually has some variable speed grinders/buffers for fairly cheap. Also good to remember that your RPM depends on wheel size as well as how fast the motor spins.

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Originally Posted by Theseus

Harbor freight usually has some variable speed grinders/buffers for fairly cheap. Also good to remember that your RPM depends on wheel size as well as how fast the motor spins.

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Am I correct in assuming that if I put 8 inch wheels on a 6 inch buffer it will reduce the rpm's a bit?

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Originally Posted by Omega1975

Am I correct in assuming that if I put 8 inch wheels on a 6 inch buffer it will reduce the rpm's a bit?

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Yep, it should. By how much, I don't know. Math was never one of my strong points.

Thanks . I cant find anything with lower rpm's even at HF.

1/4 x diameter of wheel x rpm = sfm

Smaller wheel = slower

Horn

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Originally Posted by hornm

1/4 x diameter of wheel x rpm = sfm

Smaller wheel = slower

Horn

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Im lost , whats SFM?

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Originally Posted by hornm

1/4 x diameter of wheel x rpm = sfmSmaller wheel = slowerHorn

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Soon after I made my post I had a feeling I was wrong. Glad someone corrected me.

Surface feet per minute. Sorry. I just copied what I had in my notes without thinking about the abbreviations.

Horn

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Originally Posted by hornm

Surface feet per minute. Sorry. I just copied what I had in my notes without thinking about the abbreviations.

Horn

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Thanks Horn

The larger the Dia the faster the wheel passes the work. RPM does not change with wheel size.

(RPM * Dia)/4 = SFM roughly (order of operations)
or
RPM = (12*SFM)/3.14168*DIA so (3.1416*DIA*RPM)/12=SFM More accurate but the first is good enough

I think some of the guys use 4" buffs on the faster motors.

Jeff

I have a baldor that's 1725 rpms and I have one of the variable speed deltas. To be honest I don't think the 275 rpm is going to be that much of an issue. You certainly don't want a 3450 rpm but 2000 should be ok.

Another option it to get one of the belt driven pillow block type buffers and find yourself a slower 1/2 hp motor to run it. Ya the enclosed motor systems are nice but.... one of the nice things about a pillow block buffer is that you can control the speed by the motor you select and by pulley size. The math is pretty easy for figuring the speed by pulley size. IF you would be interested in this type set up I can show you how to do the math and you can probably get that buffer down to 1000 rpm if you want.

That being said, I really don't like the idea of sticking a sharp razor into a buffer. The buffer really is the most dangerous tool in my shop. I know knifemakers who have had sharp pointy things grabbed by the buffer and thrown into themselves. If you do decide to go that route please do be careful and don't let yourself ever get so comfortable with it that you let your guard down.

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Originally Posted by Omega1975

Am I correct in assuming that if I put 8 inch wheels on a 6 inch buffer it will reduce the rpm's a bit?

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The RPM will not change but the speed of the buffing media will be faster
on a larger wheel. Something like Pi*D=mediaLength
The final answer is mediaLength*RPM

Doing some math in my head is dangerous but
swapping a out a 6" wheel with an 8" wheel
will get the speed to increase by 1/3 when RPMs
remain fixed.