how do you figure out sfpm

M

magnum .44

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Jun 12, 1999
Messages
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how do i figure out sfpm on my belt sander, at top speed (it's a variable speed motor) it will be at 1750 rpm, it has a 6" drive wheel, and a 132" belt size.
 
I think it would be calculated like this:

Your belt will move 6 x 3.14159 = 18.85 inches for each revolvation. Then 18.85 x 1750 = 32,988 inches per minute or 2,749 feet per minute.

Your belt is moving 2,749 feet per minute. To get square feet per minute, multiply this by the width of your belt in feet. For example, a 2 inch belt would cover 2,749 x 2/12 = 458 sfpm. A 4 inch belt would cover 2,749 x 4/12 = 916 sfpm. A 6 inch belt would cover 2,749 x 6/12 = 1,374 sfpm.

Hope this helps.

Carl
 
Mark a line on the belt once every foot and count how many lines go by in a minute
rolleyes.gif


That math looks right to me. Only does sfpm stand for sq ft per minute, or surface feet per minute? I don't think its sq ft per minute because bandsaws are rated under sfpm too if I remember right, and that wouldn't make much sense.

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thanks cjensma, i'll have to write that equation down for later use.
matt, i'm useing surface feet per minute, same as the bandsaws.
 
:
The formula for SFM (Surface Feet per Minute) in my aluminuim machineing handbook is
Dia.X 3.1416 (pi) X RPM divided by 12.

The SFM for the stated quanities given is
2,748.9 SFM.

The rest is not applicable to the question. Sq. feet per minute doesn't apply to machineing practices unless you are referring to materal removed.

SFM or SFPM is always Surface Feet (per) Minute when talking about how fast something is moving whether it be belt grinder. engine lathe, or drill press.


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>>>>---¥vsa---->®

The hardy adventurer just drank from a stream he thought was pure glacier fed water not knowing that upstream was being used by a herd of yaks as a giant bidet.

I said he was hardy, not smart.:-)

Khukuri FAQ
 
why do you want to know?? they have these little gadgets that arent too expensive where you stick something on the thing thats turning and aim the gadget at it and it tells you....but for your variable speed grinder, id say, find the speed you are comfortable with...in the morning when i am still waiting for the coffee to kick in i grind SLOW, but after a short time and a major caffeine dose...i turn the speed way up. but my bader 2 horse just goes fast...

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thanks yvsa,
tom, i was just wondering what the top speed was, but i'll do the same thing as you will the slow grinding when the coffee hasn't kicked in yet, or when i only need t take off a tiny bit of metal.
 
The "s" is for "surface", not "square"? Oh well, I got the math right and the definition wrong. Live and learn....
smile.gif
 
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