I think there are ways to compute the force required based on the cut depth, spindle speed and feed rate but converting force on the end mill to torque on the wheel depends of things you can't know like friction between the lead screw and nut. So I think it's best to measure. Take a cut and measure the torque required. You can measure with a torque wrench (and suitable adaptor) or by wrapping string around the wheel and hanging a weight or spring scale on the string. or by guessing how hard to are pushing on the handle. Torque is force times the radius.
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Chris Albertson
Redondo Beach, California
I think jogging the table at a decent rate is the worst case and if the motor can run the table at an inch per second (16.7 revolutions per second of the hand wheel) it can handle cutting which moves at a MUCH slower speed. But if cutting is the worse case then size the motor for cutting
Example:
The force applied tangent to the wheel times the wheel radius equals torque. But if you push on the handle, it is the handle distance from center that matters A typical motor can supply 400 in oz. of torque at low speeds The wheel is about 4" in diameter but the handle is only about 1.5 inches from the center. So a 400 in oz motor can in effect place 400 / 1.5 oz or 267 oz of force on the handle. That is about 16 pounds of force on the handle. If you need more, use a 2:1 belt reduction to double the motor's torque or get a bigger motor. If the motor is smaller, then you'd be limited to smaller cuts.
I would buy a motor that can generate about double the force required..
Typically with a small mill the spindle motor stalls out first so placing larger motor on the X or Y axis does not allow you to cut faster as spindle and lack of rigidity
So to find out how much torque is require you measure the torque to make worse case cut then buy a motor twice as strong as what you measured.
On Thu, Mar 22, 2018 at 6:27 PM, Ralph Hulslander rhulslander@gmail.com [7x12minilathe] <7x12minilathe@yahoogroups.com> wrote:
All of this discussion is really good to read..The question I have is how do you determine the torque?I do not have another machine available for reference just a manual mill and lathe.I was doing some side milling (@ 1" with 1/2" end mill on mild steel) the other day and I was surprised how much torque, I was really having to crank it.Doing end cuts I really have not noticed the torque but side milling really made a difference.So if I wanted a powered X or Y on my mill how would I determine the required torque and then all of the other infofrom this thread.Ralphwas required
Chris Albertson
Redondo Beach, California
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Posted by: Chris Albertson <albertson.chris@gmail.com>
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