Possibly upgrading a motor on a mill, what do I need to know?

[xr650rRider]

You sure your slitting saw was sharp? Some of those cheap HSS blades aren't much on steel. I bought a couple from Grizzly and they're fine on plastic or aluminum but dull within seconds on steel. I bought a Contrex carbide saw and it cut with little drag.......up until the part moved and it shattered into several pieces.

 

[WobblyHand]

Don’t you want a small motor pulley and large spindle pulley for a slower spindle speed?

You are right. I want a small motor pulley and a big spindle pulley, which is loads easier to do. So if I could get a 120mm pulley to fit on the spindle end, with the existing motor pulley, the unit would go 1/3 speed. If I also changed the spindle end to 30mm, then it would be 1/4 speed.

 

[WobblyHand]

You sure your slitting saw was sharp? Some of those cheap HSS blades aren't much on steel. I bought a couple from Grizzly and they're fine on plastic or aluminum but dull within seconds on steel. I bought a Contrex carbide saw and it cut with little drag.......up until the part moved and it shattered into several pieces.

Niagara saw. It is sharp. It is still sharp after all this.

That's why I am hesitant about a carbide saw. I'm sure they are great - until something happens. Then say goodbye to it. Just like a Micro100 boring tool, awesome as long as it's intact.

 

[WobblyHand]

Here's a pulley that might work. Large pulley 125mm diameter, normal one at 60mm. For low speed, it will be 40mm on motor and 125mm on spindle. Reg speed (stock high speed) 60mm on spindle, 60mm on motor. For now, I will just make the spindle dual pulley. Found the J spec angle to be 40 degrees. Here's a preliminary model of the spindle pulley. Since I don't cover the belts, I actually could make the pulley wider.
Side view:

Topview:

I didn't bother to radius some of the Vee's in the drawing. The part won't have the sharp edges.