NWSG questions (3 step pulleys, motor speed)

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obsessis

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Jul 2, 2009
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i'm trying to find a motor for the NWSG and I have a couple questions I hoped you guys could answer.

with the 3 step pulley system tracy sells, why do you need one at the drive shaft and one on the motor? couldn't you just have a regular pulley on the motor? wouldn't that make it a system with 9 different speeds?

is the 3 step short enough to fit on a motor with a 1.75" long shaft? i was told by a motor seller that the model 56 casing (5/8" shaft) usually has a 1.75" long shaft and to make sure the pulley fit.

after reading about other grinders, i've seen a lot run 1 HP 1725 RPM motors. is 1 HP strong enough for the NWSG? what would the difference in RPM's produce in a NWSG with a 3 step pulley setup?

why do people get a 3 step when a 4 step is available? is the 4 step bad?

thanks in advance
 
You need stepped pulleys on each to keep your belt running strait. You install one with the small diameter out, and the other one with the smallest diameter in. If your belt does not run straight, you put stress on both shafts. 3 stepped pulleys will fit on a 1.75" shaft, but of course the shaft may hide inside a bit. A 4 step may not fit well. Hope that helps.

Milt
 
3 steps are good enough in most cases. Generally, the motor shaft is often too short for a 4 step. If you have a long shaft on your motor (hah!) the 4 step isn't a bad way to go.

I use a 3 step myself on my garage grinder. I have DC variable setup on my shop grinder and will switch to a VFD setup when the DC dies.

Increasing/decreasing the RPM via these step pulleys will not increase or decrease your torque. In other words, the step pulleys won't let your motor "do more" like a block and tackle allows heavier loads to be lifted.

A1hp can be used but it will drive you to drink. You will be able to grind with a contact wheel fairly well but when grinding on a flat platen, you will really strain the motor and probably stop the belt often enough to be really annoying.
 
I recently built the NWSG and have a 1.5HP Leeson on it and Tracy is right about the flat platen straining to motor. I can stall the 1.5 HP pretty easily and if I had to do it over I would put a 2 HP or add another 220 line and go for more. More is better.
 
thanks for the answers.

another question, what functional difference do the RPM's make? the ones I'm looking at are either 1725 or 3450 RPM. What is the difference between the two with the same HP?
 
obsessis said:
thanks for the answers.

another question, what functional difference do the RPM's make? the ones I'm looking at are either 1725 or 3450 RPM. What is the difference between the two with the same HP?
Click to expand...

either motor will work and the torque is basically the same. in theory the faster a motor goes, the less torque it has but it is slight and momentum energy in the armature helps recover some of that loss in use.

in practice for knife grinding, generally, you go full blast hogging off excess metal and as you get closer to being finished you go slower. Slower is better at the end for control.
 
Okay, I give - what's a NWSG? If that means "surface grinder" point me in the right direction! Please.
 
NWSG
No weld sander grinder, Tracy at usaknifemakers sells the plans and its a KMG style sander.
Chris
 
Okay, I've heard em call that the NWG. :) That "S" threw me; kind of got my hopes up for building a surface grinder.
 
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