Powermatic 3520B question

[Dan Case LR]

I'm considering buying a 3520B during the Black Friday sale, but have a quick question for those who have one.

If the motor is running in the forward direction and you flip the toggle to reverse, does the controller do an orderly slow/stop/reverse cycle?

This is the way most controllers would work, and since they haven't arranged things to require a manual stop before reversing I'm assuming this would be the case...but I've learned not to assume (the hard way, of course). "The only stupid question is the one not asked prior to the stupid mistake."

Thanks!

D.

[kevin nee]

I have a 3520B, you can switch from forward to reverse and the controller will adjust the speed down then reverse the rotation. I stop the rotation and restart after switching, it just takes a second and it just does not make sense to go from one direction to the other with out stopping. My opinion probably just old school. The dial that controls the rotation does go to 0 RPMs or you can stop it with the switch. I got my 3520B in 2009 and use it daily and have been very happy.

[Don Bunce]

Yes, it will, but if you don't have a set screw to secure your chuck or faceplate, it will probably unscrew it. Best bet would be to turn the speed knob down to zero, then reverse directions, then bring the speed back up to where you want it. Only takes a couple seconds.

Congrats on the new lathe, you will love it.

[John K Jordan]

I asked that question years ago.

The direction change uses the deceleration/acceleration parameter set in the VFD controller to slow down then speed up the other direction. (You can set this to a different number if you want either a slower or faster direction change.)

If you just flip the direction switch the slowdown and speedup is exactly the same as if you hit the stop button, flipped the direction switch, then restarted. The only differences are you don't wear out the start/stop button as much and there is a short delay depending on your reaction time turning it back on. I personally don't like to turn the speed down before reversing since it takes longer and if I'm doing something where I want to keep the speed the same I simply don't have to pay attention to get it the same or close.

BTW, a new VFD I just added to one lathe has a feature in the programming to use a secondary deceleration/acceleration interval as well as use a curve other than linear. I haven't tried it yet but from the manual I think I can program it to detect the position of another switch I would add somewhere. This would let me change decel/accel times simply by flipping the second switch. If I turned large bowls I could flip that switch for a more gradual slowdown; for small spindles I might use a quicker, more abrupt start and stop.

JKJ

[Reed Gray]

The ramp up/ramp down speeds of the phase converters can be varied. If you hit the reverse switch without turning it off first, or going to 0 rpm first, the programming still kicks in so it goes down to 0 rpm, then ramps up again. The speeds as they come are 'supposed' to be set so things won't come off. Those speeds would put a lot of stress on the motors. I did this reversal a number of times with my A by accident. It didn't bother the lathe at all.

robo hippy

[Lee Watermann]

Yup, the chuck will unscrew. Don't ask me how I know.

[Bill Boehme]

I save wear and tear on my speed control pot by just hitting reverse when sanding. I keep the lathe speed fairly low when sanding so there is no need to worry about a piece unscrewing itself.

[Justin Stephen]

Yup, slows down and switches directions smoothly. However, I almost never do that in case it causes extra wear and tear on the lathe. I almost always stop it first. Like Bill, I sand at a very low speed (when power sanding anyway) so I have never had an issue with a chuck or plate unwinding on me.

[Thom Sturgill]

I believe a few years ago a Powermatic/Jet tech stepped in and answered this saying that the controller is designed for just that, otherwise they would FORCE you to stop, reverse and re-start. I believe the new griz is programmed that way.

[Faust M. Ruggiero]

As Thom said, your VDF is designed to stop then reverse. Lathe controllers have an electronic brake that is supposed to stop the lathe. I owned a Powermatic lathe for several years before selling it and buying my current lathe. I rarely used the grub screws on the chuck because invariably I would forget to loosen them before trying to remove the chuck, leading to a scarred shaft. That didn't hurt the shaft it merely made mad at my forgetfulness. If I still owned it I would replace all the grub screws in my chucks and face plates with brass tipped set screws. The Powermatic lathes do not have hardened shafts. My new lathe does and using the grub screws is imperative or the chucks will unthread themselves if I reverse or even if I shut off the lathe with a heavy piece mounted on a chuck. Don't be afraid of a 3520b. It is a great lathe.
faust

[Dan Case LR]

Thanks everyone for your comments and information. I've worked with enough VFDs that I expected the answer to be pretty much what it was--but still felt the need to confirm. I can make my wild-hair idea work without doing anything to the factory wiring that can't be 100% restored to factory in a few minutes.

Now, all I need is patience waiting for Friday to come so I can order that 3520B. And patience waiting for it to arrive. And a bunch of money. :D

Thanks!

D.