A Technical Question Regarding Variable Speed Drives

Signed-In Members Don't See This Ad

Fine Engineer

Member
Joined
Nov 17, 2021
Messages
246
Location
Carson City, NV
So I have a WEN 3421 lathe with the variable speed drive. Does anybody know if I could use a variable voltage power supply to get lower speeds?
My thought is that for doing some fills with epoxy, you need to keep it rotating slowly so that the epoxy doesn't sag while it cures. The slowest speed I can get from the dial is about 700 rpm, but I'd like to go to 1 or 2 rpm. Normally I'd just connect things up and see what happens, but I think there's a good chance the low voltage could fry the electronics in the speed controller, so I thought it best to poll the experts here first.

Any ideas?
 
Signed-In Members Don't See This Ad

monophoto

Member
Joined
Mar 13, 2010
Messages
2,343
Location
Saratoga Springs, NY
Jeff

I would be concerned that coupling a variable voltage supply with a variable speed controller could be a recipe for trouble.

An undocumented feature of my lathe (a Turncrafter) is that there are three potentiometers inside the speed control box that can be tweaked to adjust the speed range. I spoke to one of the Tech Support people at PSI who walked me through the process of adjusting the speed range using those pots. It was really simple - just use a screwdriver with an insulated handle to adjust the setting of two of the potentiometers while watching the speed display to see the impact. One is marked L and controls the low end of the speed range, while the other is marked H and controls the high end. The third potentiometer is marked F and I was told to not touch it - don't know why, but I am well trained and follow instructions.

I don't know if the Wen has this feature, but I would be a bit surprised if it did not - I can't imagine that lathes in this price category are all that different. You might try calling Wen Customer Support to ask for their advice.

Having said that, my experience is that while the Turncrafter design does allow for tweaking the speed range, in fact it's very difficult to get extremely low speeds, or to get any significant differentiation between speeds below, say, 50 r/min. But I have had good experiences using my lathe in speeds down to around 50 r/min for extended periods while finishes 'set up' - sometimes referred to as 'rotisserie finishing'. It works especially well with finishes such as solvent-based polyurethane that set up in about an hour.
 

Fine Engineer

Member
Joined
Nov 17, 2021
Messages
246
Location
Carson City, NV
Jeff

I would be concerned that coupling a variable voltage supply with a variable speed controller could be a recipe for trouble.

An undocumented feature of my lathe (a Turncrafter) is that there are three potentiometers inside the speed control box that can be tweaked to adjust the speed range. I spoke to one of the Tech Support people at PSI who walked me through the process of adjusting the speed range using those pots. It was really simple - just use a screwdriver with an insulated handle to adjust the setting of two of the potentiometers while watching the speed display to see the impact. One is marked L and controls the low end of the speed range, while the other is marked H and controls the high end. The third potentiometer is marked F and I was told to not touch it - don't know why, but I am well trained and follow instructions.

I don't know if the Wen has this feature, but I would be a bit surprised if it did not - I can't imagine that lathes in this price category are all that different. You might try calling Wen Customer Support to ask for their advice.

Having said that, my experience is that while the Turncrafter design does allow for tweaking the speed range, in fact it's very difficult to get extremely low speeds, or to get any significant differentiation between speeds below, say, 50 r/min. But I have had good experiences using my lathe in speeds down to around 50 r/min for extended periods while finishes 'set up' - sometimes referred to as 'rotisserie finishing'. It works especially well with finishes such as solvent-based polyurethane that set up in about an hour.
Thanks for the info Louie, that helps. After thinking about it, 50 rpm should be more than slow enough. I'll take a look and see if the adjustable pots are there.
 

jttheclockman

Member
Joined
Feb 22, 2005
Messages
17,020
Location
NJ, USA.
Never hook a speed controller up to a VS tool that is already controlling speed. Just my thoughts. People ask this all the time with scrollsaws. being an electrician that is my professional opinion.
 

rixstix

Member
Joined
Jan 10, 2007
Messages
310
Location
Canistota, SD USA
Talk to the lathe support folks. They might talk you through an internal adjustment to get lower speed realizing that might affect the top speed. PSI did that with me to get sub 50 rpm on my PSI lathes......just like Louie said. Sometimes I would have to jumpstart the lathe using the handwheel but once started it ran and ran.
 
Last edited:

Fine Engineer

Member
Joined
Nov 17, 2021
Messages
246
Location
Carson City, NV
There are slow rpm set ups for turning objects like fishing rods. Look on internet, I'm sure they were cheap
I had a math teacher that developed a 12V rotisserie device for camping, but fishing rod people found it and it was perfect for them. He sold far more of these to fishing rod people than campers and backpackers.

Unfortunately, he found that the business was just enough to be an inconvenience, and not all that profitable, so he sold the plans and supplier lists to several people and closed up shop.
 

farmer

Member
Joined
Jun 16, 2012
Messages
807
Location
NV
I had a math teacher that developed a 12V rotisserie device for camping, but fishing rod people found it and it was perfect for them. He sold far more of these to fishing rod people than campers and backpackers.

Unfortunately, he found that the business was just enough to be an inconvenience, and not all that profitable, so he sold the plans and supplier lists to several people and closed up shop.
There are two pods on the circuit board on the Viable speed controller converter .
These pods have super small screw in them ,one screw adjust minimal rpm's
Post a Pic of your speed controllers circuit board .
Adjusting to lower the rpm also removes that many rpms off the top speed .
I have 3 matching lathes so for lower rpm's i swicth the controller
 
Last edited:

dogcatcher

Member
Joined
Jul 4, 2007
Messages
2,229
Location
TX, NM or on the road
$25 for a sewing machine motor on eBay. A home made pulley system hooked up to a "looks like a wood lathe" system to mount a mandrel. Speed control with a router speed controller. I built one for fly tying any speed from 0 to 100 RPM. I used scrap wood mostly plywood. My cost was about $55, 25 for the motor and same for the router controller.
 
Top Bottom