I am cutting alot of aluminum these days and the Porter-Cable router has got to go! I've already ordered my treadmill motor/controller... am looking hard at the sherline industrial spindles. Is there any difference between these and the "standard" sherline spindles/headstocks ?? (not interested in high speed). Thanks

Some of them have ER-16 collets, the standard Sherline spindles have a Morse #1 taper.

Both should be OK as long as you're doing smaller stuff. If you plan on taking big cuts in aluminum, look for an Asian mini-mill spindle with an R8 taper. Not nearly as accurate, but a lot sturdier. R8 tooling is a lot cheaper, too.

Thanks Neil, let me re-phrase....
Sherline replacement headstock #30100 - #1 Morse/dual-pulley = $102
Sherline Industrial headstock #6502 - #1 Morse/dual-pulley = $175

Any difference internally ??

The industrial headstocks come with a flat mounting surface with 2 tapped holes and a keyway slot. I'm pretty sure the replacement spindles come with dovetails machined into them. Not sure why there is a price difference though.

The industrial headstocks come with a flat mounting surface with 2 tapped holes and a keyway slot. I'm pretty sure the replacement spindles come with dovetails machined into them. Not sure why there is a price difference though.

This is correct, the industrial version attaches via two 1/4"-20 screws and the precision-ground head key. I would go with the standard spindle, and spend the rest on tooling :)