I used to have a combination 6" disk sander/vertical belt sander similar to the one pictured below.
It would slow down to 300 RPM, which worked very well for sanding plastic and thin sheetwood.
I have been looking for a replacement, but the slowest one I have been able to find only slows down to 1,500 RPM, which seems very fast to me.
Does anyone have any suggestions?
I am not interested in a miniature power tool version. The 6" disk size worked very well.
Thanks.
-Kevin
Kevin.
I’m not an electrical engineer but have you thought about a reostat or VFD? I do know that AC motors lose a lot of torque running slower and heat up quite a bit unlike DC motors. My ceiling fans are on reostats so I can turn them way down. But they hum a lot and can be stopped easily.
Pete.
I was also going to suggest a Variac:
Here is a link to a DIY controller:
https://www.instructables.com/Variable-Speed-Controller-for-AC-Motors/
Probably a lot less expensive if it works.
Losing torque is not a concern. With the thin materials I am sanding, the motor is way overpowered anyway.
I looked for an external speed control for power tools, but found nothing.
I am not familiar with the Variac. The sander has a 120 volt single phase AC motor. Is this compatible.
I have also never used a rheostat with AC current. I have no idea how to make this work.
-Kevin
Not an electrician, either. But I believe that it is basically like a light dimmer switch. If anyone you know has a sewing machine, the foot pedal they use to control the machine’s sewing speed is, I think, very similar.
If it helps, I’ve got one of those Ultimation sanders. Designed by a modeller for sanding wood and plastic.
Since is is not powered, you have infinite control. IIRC, the motivation to create this was someone building a wooden snow shed in O scale and needing a lot of accurate angles.
Not cheap, but well made.
Basically like a light dimmer switch but important to note that a motor speed control is rated for a heavier draw - never use a light dimmer switch to control a motor.
I can’t imagine why a good motor speed control wouldn’t work in this situation just be aware of potential motor heat.
And, like others, I am not an electrician so take the advice for what it is worth…
Kevin, I know very little about variable speed disc sanders, but Shopsmith sells a line of such sanders with variable speeds as low as 700 RPMs.
https://www.shopsmith.com/mark4/m4-disc-sander.htm
Maybe this will be helpful to you or maybe not.
Rich
The Shopsmith is just way too big. This would be only of only two bench-top tools in my house. I also have a smallish drill press. I just don’t have room for a real wordworking shop.
There could have been something wrong with my old one only letting it run 300 RPM. That I do not know. It was perfect for precisely sanding basswood sheets.
I do have a pedal from an old Pfaff sewing machine. Would that be usable as a speed control maybe?
-Kevin
Thanks for the link Neal.
That led me down a hole of reading user reviews, technical specs, YouTube videos, etc, and now I am completely confused.
Some people say these devices will overheat, will damage the tools, or not work at all. Others say they are a panacea for everything I need to do.
I will be using the tool only intermittently to true building walls and other casting/pieces.
Now I am so confused.
-Kevin
A word of caution: single speed AC motors are usually induction motors. They are designed to run at ~3600 or ~1800 RPM. If you use a reostat or Variac to lower the speed the motor will try to maintain its speed and just draw more and more current until it overheats and destroys itself. As the TV commercials say, do not try this at home. Small variable speed motors are designed to do this and are either series wound or permanent magnet. Dremel tools and model train motors are examples. Larger variable speed tools such as drill presses or sanders use multiple pulleys to change speeds.
Charlie - Northern Colorado