A bit on electric motors for the forge shop. When spending hard earned dollars on motors for your blacksmith shop, there are many terms that may confuse. Lets first look at some of the things that kill motors. First and biggest in a metal shop is dust, especially conductive dust. Too much heat is of course bad. Pulling too much power, for too long will overheat and there you are with the too much heat.
So when you are looking for a motor, you see advertised terms like ODP, compressor duty, TEFC. An ODP is open drip proof. Has an internal fan and draws air from your shop and blows it through the inside of your motor. Bad if your shop is dusty, and yours is, don't lie to your self :)
Compressor duty motors are rated for the higher starting loads of a compressor but are almost always an open design and suck air through the internals. TEFC, that is Totally Enclosed Fan Cooled. These have an external fan on the end opposite the shaft that is OUTSIDE the motor case. They blow air over the outside of the motor, cooling it without sucking in all that dust from your shop. (See a bit on respirators for how to not suck that same dust into you) A TEFC motor is usually more expensive then the others. They are usually better built and last longer even in a clean environment. Buy the TEFC motor.
Another way to kill motors is to run them at a voltage that is lower then they need per the nameplate. This is not electrical engineering 101 so in short less volts more amps. Amps are what makes the heat.(Simplified for all the folks that took electrical engineering 101) Si... if you undersize the wires, and run them too far for that size the volts drop and the amps go up and you buy motors more often. If this sounds like mumbo jumbo, it is, hire a mumbo jumbo translator called a licensed electrician. Then you will get a circuit that is to code and will tend to keep you alive and the code inspector smiling.
On motors you often see a nameplate spot for S.F. That is service factor and indicates how hard the motor can be used and expect to get a useful service life. Used hard means things like how much time in any hour you run the motor and at how high a load. Cheap motors often have as low as a 0.85SF. Really good motors will be better then 1 and 1.25SF is very good.
There are many standards for FRAME. A really good concise guide is the motor selection guide in the front of the motor section in the Grainger's catalog.
This just scratches the surface of motors. if you want to know more read that section in the Grainger's. If you find that interesting there is lots more in electrical Mumbo Jumbo translation classes at the local tech school. Enjoy.