I am working on a design for a small lathe that could double as a horizontal drilling machine like a Westhoff.
My plan is to have specific geared speeds, rather than continuously variable speed.
I am wondering what the best type of motor would be. Cost is no object, but it needs to be compact, no more than 6" in diameter and hopefully less.
Startup torque is not required, because in this type of application you can always start the motor unloaded; in fact, even if the motor had zero startup torque I could potentially add a small starter motor to start the main motor, if that would be better.
It would run on normal AC household current
My thought is to find a motor with a high peak torque rating and then just run the motor at that ideal speed, using gears to adjust speed as necessary
Obviously, the more horsepower the better
Some additional points to consider:
For the class of lathe/mill intended, the target HP would be between 1 HP and 2 HP
A lighter or more compact motor is desirable, so that the overall footprint of the lathe is minimized. Therefore, a motor that has relatively high HP for its weight/size is desirable.
High-end lathes use a slipping clutch to protect the motor and gearing from excessive loads. The clutch is set to a torque such that the maximum possible load would not break any of the teeth in any of the gears.
A single speed motor is fine because a high-end lathe/mill will have a gearing system that determines the RPM of the machine and allows it to be varied.
It is important that the motor have strong inertial force because when metal is being cut sometimes a hard inclusion will be present so that the load on the motor can unexpectedly spike up for a fraction of a second when the cutter hits the inclusion.
It is important for the lathe's speed to be as consistent as possible because if the lathe has variability in speed as the load varies, then what will happen is the quality of the finish of the cut will be degraded. What is wanted is for that that motor to keep turning at exactly the same speed regardless of the variability of the load.
Cost is not a factor, because other parts of the lathe will be much more expensive to construct than the motor, so the motor is a relatively minor part of the cost to construct the lathe.
What type of motor best fits these characteristics?