Your numbers seem reasonable. Your original premise, that you can slow
a motor down 90% and still use it normally, is not.

185 fpm is a little high for metal cutting but it will work. 80 is a better
all-purpose target. Slowing a little 1hp motor down 50% is about the limit,
and be aware that many motors are fan-cooled so when you slow them down you
are also removing their cooling capability.

A nifty 5:1 gear reducer would help you a lot. A 10:1 would be better.

GWE

Wally Blackburn wrote:

I have one of the old Delta 14" wood bandsaws that I am using for
metal cutting. I am using a 3-phase 1HP motor with a VFD - so I can
slow the motor way down for metal.

To be honest, I've never used a bandsaw before, so I am learning the
hard way, and I think I just huffed my first blade (14-18TPI Morse
Bi-Metal). Anyway, I was just guessing at speeds to run the motor,
and I thought I would calculate the SFPM to see where I really needed
to be. Looking at the speeds metal bandsaws are advertised at, I
think I need to slow down. Could you guys just check my math?

- Bandsaw drive wheels are 14" diameter. 2 * pi * r = 44" or approx.
3.7'

- Motor has 2.5" pulley, pulley on bandsaw wheel is 6" for 0.42
reduction

So, if a rev of the drive wheel moves the blade 3.7' and it is driven
at 0.42 of motor speed, SFPM should be (3.7)(0.42)(Motor RPM), or
approx. 1.5 * Motor RPM.

If that's true, getting the fastest speed of a Wilton metal bandsaw
(278 SFPM), I would have to run the motor at 185 RPM! If my calcs are
correct, then I need more reduction between motor and drive shaft.

Does this sound right, or am I missing/misunderstanding something?

Thanks,
Wallace