So what if my bandsaw runs at 2x speed?

[TDKPE]

I'm not seriously considering leaving the driven pulley the same. Just curious about it.

I didn't think you were, but it's an interesting mental exercise nonetheless, as I'd never considered what would happen if speed was doubled. 


My early 40's Craftsman 12" runs at about 2000 ft/min, by the way.  Though that's not necessarily something that should be used as an example of the ideal.  The recommended motor was only 1/2 hp.

[daddo]

Drive pulley (@3,600 rpm) 1.5" Drive to 6", then 3" to 6" would get you just under 3,000 fpm.

Not sure where my is set. I set it when I got it and it's been fine since.

The other one I use to cut metal is 500 fpm- as slow as it goes.

[®smpr_fi_mac®]

Using the formula TD gave me, I came up with various options.

driven/drive pulley sizes

8/1.9
10/2.375
12/2.85
14/3.33

My current setup is 4.64/2.21. A 14" driven is too large, and a 12" is uncomfortable large; I wouldn't be able to fab up a very good guard for it.

So I'll give a 10" a try, which will keep me close to the current pulley size and see where that gets me.

[TDKPE]

You could also use a 2-1/4" OD (2" pitch diameter) driving a 9" OD (8.75" PD).  (2.00/8.75)*3450 = 788 rpm, which is very close to the 820 rpm target.

http://pulleys.congressdrives.com/item/a...0900x075kw

http://pulleys.congressdrives.com/item/a...0225x062kw (I guessed at the bores, and have no idea what you really need)

Since the motor is turning twice as fast as the original, for the same hp and blade speed, the belt tension on the working side will be half that of the original.  So you can use a smaller driver than you would with a slower motor.  Looked at another way, the 3600 rpm motor will output half the torque (for the same hp), so again, a smaller sheave can be used without belt slip. Just use a cogged belt (AX), or a good quality fractional hp belt (4L) with milled sides rather than fully cloth wrapped.

Cast iron sheaves from Surplus Center will cost about the same, but do be careful about picking the size based on the A-section datum diameter, NOT the OD.  They will have a larger OD because they accept both A- and B-section belts, so the grooves are wider and deeper to accept the wider B belts.

[Pirate]

When I put a riser, and a 1 hp motor on my old Delta 14" bs, I used a motor pulley 1/2 the diameter of the wheel pulley, and with a 1725 rpm motor, now have 3160 sfpm. It works great at that speed.
Here's a link to calculate sfpm.
http://vintagemachinery.org/math/sfpm.aspx