I'm in the planning stages of an idea I have for a low-cost homemade CNC tubing cutter for making semi-precise curved cuts in basic thin-walled EMT electrical conduit. For my first proof of concept design, I don't want to spend huge money for a plasma cutter, so I thought I'd try using a basic rotary cutting bit in a mill-type cutter setup. I've read that should work on soft metals like aluminum or brass, but I've never seen EMT mentioned. (FWIW, my requirements are pretty low on precision and speed. I'd be happy if my cuts were within .1" and just about any feed rate would do.)
1) So that I can size a motor for the prototype, what ball park should I aim for as far as spindle speed, motor power and what type of bit should I plan to use? High speed cutting would be nice, but isn't paramount. I just want something economical that will cut through the material reasonably well and won't burn up bits too fast. As far as bit size/cutting width, I'd like to use the smallest bit that still would give good bit life, and shouldn't break. I think all cuts would always be through the wall of the EMT, not partially through, so only plunging and side-cutting would be going on. If I guess too small/cheap and burn up a motor, I won't mind upgrading it, but I'd rather avoid spending too much on the motor upfront. (IOW, if a .5hp motor is probably likely to work, I don't want to over spend $300 to get a 2hp motor "just to be sure")
2) Are there good techniques to use if my motor is slightly underpowered to accomplish the job? (E.G. Would it help if I made multiple passes at increasing depths? Slower feed rates? Something else?) I know a rotary cutter isn't ideal for cutting metal, but I'd like to get it to work for this first prototype.
3) If a rotary tool with a milling bit proves unworkable, are their any other "Plan B" cheap ways to cut EMT in a CNC machine?