Reducing my lathe speed

[Eric Gourieux]

Reed's post about slow speed sanding prompted me to ask you experts a question I've had for awhile. I have a Nova DVR XP with a minimum factory-set speed of 100 RPM. That is more that adequate for most of my sanding, but there are times when I would prefer a slower speed. Does anybody know how to change the minimum RPM setting? Have you received help from tech support walking you through a change like this? I would assume they would be hesitant to help due to liability/torque/warrantee or whatever issues go with it.

[Bob Hamilton]

Hi, Eric:
I doubt if it is possible. When the DVR lathes were first introduced they had a minimum speed of 250 rpm. The "next generation" of DVR lathes had the minimum speed of 100 rpm and at the time there was a kit available that would let people that had the original model upgrade to the new minimum speed, but the kit consisted of a new control board that needed to be installed, not just a setting change. The XP model and the new 20" model both have the same 100 rpm minimum so I suspect there is some sort of inherent limitation to how slow the digital variable reluctance motors can go and still perform useful work.

You could make a large disk to mount on the outboard hand wheel with a belt groove around the outside and drive it with a separate motor (or treadle) for lower speeds if you feel it is worth the effort.

Good Luck!
Bob

[Michelle Rich]

I would not touch it.

[Reed Gray]

I asked Nova about that in San Jose. I have to have slower speeds to sand out my warped bowls. It is not possible on that lathe. With the 3 phase converters, it can be done. I am not sure about the vector drive motor that is on my Robust Liberty. I have to ask Brent English about that one. On the PM and Jet lathes, their minimum speed is 50 rpm. When I bought my 3520A 15 or so years ago, it would go down to almost 0 before turning off. They changed that with the B model, or maybe even before that. When I asked why, they said you would over heat the motor and fry the electronics. Owners are now locked out of the phase converters. I told them that I had sanded out thousands of bowls at slower speeds and had no problems. They said that was impossible, and that their lab tests said the motor would over heat. I had my American Beauty programmed for those speeds, and the motor runs cooler (hand test) than it does when I am turning. It was also changed to run at higher rpm in the speed ranges. There is a thread on the AAW site, under tips, about the code for getting into the converter and reprogramming it. Some use the slow speeds for applying finishes that may droop or sag. There is no load on the motor when sanding, well, when power sanding, and none on the finishing, so no heat is my guess. No other reason to run that slow though that I can think of.

robo hippy

[Eric Gourieux]

Thanks for your replies.
Bob, that may be worth the effort one of these days. I'll keep my eyes out for an old motor that would work.

[robert baccus]

Years ago I rigged a 16" Griz to slow down the rpm from 500 to slow for roughing out bigger bowl blanks just like Bob indicated. Total cost $2.50 and worked great. Another use for slow rpm's is spraying lacquer ect. Actually I sand fast--even 80 grit at high rpm and low pressure leaves tiny scratches.