Switching to Reverse with Lathe Running

[Bob Bergstrom]

Just noticed Nick Cook demoing the Powermatic 24-32. He throws the switch to reverse while the lathe is running in the forward direction. Does anyone else do this? Isn't it hard on the motor. I would suspect that because he was turning a small spindle he could. I am sure too much resistance would kick in the override and he would be pulling the plug to reset the speed control. I have a 3520 and always shut it off before changing directions.

[Roger Chandler]

I just think it makes sense not to chance a short out on an inverter or motor.......I always shut the lathe off before reversing!

[Gary Max]

Remember it's a 3 ph motor---- it doesn't hurt anything.

[Mark Hubl]

What you do in a rent a car stays in a rent a car! From what I have seen Nick prides himself on speed, so this is probably just some more schtick.

[Baxter Smith]

I have done it a couple of times by accident and often wondered what effect it might have.

[Faust M. Ruggiero]

Most variable frequency drives allow you to do that. I do it all the time with my 3520. The lathe slows down and stops then reverses. Oneway lathes also work that way. Of course, I only do that between grits when sanding so I don't do it with a heavy blank. That would be tempting fate.

[Dennis Ford]

It does not seem natural to be able to do this but: as Faust wrote; it is not really a problem with most variable frequency drives, they use the programmed acceleration/deceleration rate to slow down before speeding up in the other direction.

[Fred Belknap]

Mine just goes off when I switch direction, have to hit the on button to get it going.

[Norris Randall]

In 195? I got a tour of a mfg. plant in Toccoa GA. Robert Gilmour LeTourneau built earth moving machinery. One of the first exhibits was a display of an electric motor inside a glass enclosure. A pump was turned on to start a heavy spray on the motor. Switch was thrown, motor had a large metal "flywheel" with a painted mark. The switch was thrown and in a "split second" the motor was up to full speed in the opposite direction. Those motors drove individual wheels on one of the first huge "drag pan" earth movers.

I also remember the guide saying, GE and Westinghouse had said "it could not be done"

[Richard Jones]

Ditto to what Faust said. Only when sanding.

As an addendum, I also reverse the lathe when removing chucks.

[Russell Eaton]

I bought a 4224B that Nick did a demo on. I asked this very question of him and his response was it is not a problem. I have done it a couple of times and the motor slows at a faster rate then reverses and starts back up. I still try to cut it off first then reverse, it just seems like the better way to me.

[Steve Schlumpf]

I did it a few times by mistake with my Jet 1642 and no problem but I wondered if it would hurt anything. When I picked up my Robust, I asked Brent English that exact question and he walked over to the lathe and actually demoed how it brakes the lathe speed and then ramps back up in the opposite direction. The vector drives are designed to be able to do that! The only time I use the reverse function is when I am sanding the form. I know it will work on large heavy blanks because I have done it - just to prove it could handle the mass... but the only time I actually want to reverse the lathe is when sanding.

[Faust M. Ruggiero]

Steve,
Being the lazy and technology whacko that I am, I also use it to insert and remove the buffing wheels on the buffing system. Richard, I am always worried I might catch a finger in a chuck when removing or inserting so I don't do those under power.
faust

[Steve Schlumpf]

Now that you mention it, I have done that with the buffing wheels but my biggest use of the reverse function is when sanding.

[Dale Miner]

Be sure to have the chuck set screws set to lock the chuck on the spindle before doing the reverse thing. Not much fun to have a heavy blank and expensive chuck flopping about and landing on the floor (or your foot).