New warco 250 v lathe

[JasonBModerator @jasonb]

Strange that he stalled teh 290 which is supposed to have more torque than the DC driven 280 etc.

I stalled my 280 the first time I did a 9" dia iron casting but have not stalled it since, just learnt what depth of cut and speed the machine could handle and stick to that, maybe he is trying to use it as he would a commercial machine.

J

[Rik ShawParticipant @rikshaw]

"maybe he is trying to use it as he would a commercial machine."

You are right Jason and therein lies the reason for his disappointment. Like you I think it is a matter of not pushing it to much. Sure, things will take a little longer but a relaxed pace is no bad thing for the blood pressure.

Rik

[JasonBModerator @jasonb]

Not always so Rik, on the large dia stuff I find that the smaller depth of cut can be run at a much faster speed so one really cancelles the other out, the higher speed also keeps the motor cooler as well as letting it run where there is more torque.

Take this 10" flywheel, book speed would be in the region of 30rpm but I'm cutting at 300rpm and a 0.030" depth of cut. So either 10 cuts at 0.03" or one cut at 0.3" would take about the same time. Don't think even a Hardinge would want to do it in one pass of 0.30" in the same time.

J

[Bill Davies 2Participant @billdavies2]

First post.

If you double the diameter, you halve the speed. The speed of the work moving past the tool remains the same.

The torque has doubled (half the speed) but so has the radius, so the force acting on the tool is the same.

Thus, the same depth of cut and feedrate will work at any diameter. This is true for geared heads with a fixed speed motor, but I would think not for variable speed drives.

Bill

[JasonBModerator @jasonb]

WelcomeBill

As you say with a geared (or belt) head lathe the motor is running at its optimum speed regardless of the spindle speed. However with the DC variable speed motors as the speed is reduced at the spindle it is also reduced at the motor and they can be found lacking especially when the leverage of the tool on a large diameter workpiece comes into play.

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