Taig Microlathe operating on a surplus treadmill motor. I can cut 1/8"deep cuts on 12L14 steel by using a 2.5 to 1 reduction set of pulleys and slowing to the motor spindle speed to around 100 rpm. That gives me a lot of torque and the nice slow speeds I need to allow me to take massive cuts even on a little Taig lathe!
Here you can see my 7 x 10 running on a treadmill motor. It operates with two shop made pulleys providing a 3:1 reduction ratio to the lathe spindle. This gives incredible control especially when performing treading and when parting off operations.
I first began to consider the use of these motors after I got my first variable speed tool. I became so spoiled with the ability to change speeds as needed on the fly, that I vowed to never use a tool without the luxury of variable speed. My 7x10 Minilathe's motor blew after 5 years of faithfull service so I had to come up with a replacement.
Until now, motors that provided high-torque variable speed control were too expensive. there are a few companies that deal in surplus motors, many in new condition. The best type would be a DC parmanent Magnet Motor but you they tend to be expensive. Next and probably the best choice is a Variable Speed Treadmill motor with a speed controller. If you can rip one out of an old unit, it would be ideal. I was licky enouogh to find a couple of TM units from Surplus Center in 2000 but they no longer seem to have any. However they do carry a lot of different types of motors all at surplus prices. ANything in the 1/2 - 1 hp range would be perfect.
Another source and one that I've used ini the past is a DC variable speed motor from an old wood working scroll saw. Not a jigsaw a scrollsaw. These are perfect and measure about 3" diameter by 7-8" in length. You simply use the controller the saw comes with. My saw's scroll arm bearings were shot but the motor was perfect. I incorporated it in my homemade Milling Machine I feature in many of my videos.