Low speed for 12" disk sander

[Pete Staehling]

Okay so I have been happily using my Harbor Freight 12" disk sander for a few years. I never really gave it much thought, but it is really hard to not burn cherry when sanding it.

I developed the habit of doing some small sanding operations when the sander was spinning down and realized that I'd really like a lower speed sander, maybe really low speed. That got me wondering about variable speed options or maybe just a lower single speed than the Harbor Freight comes with (1725 rpm I think).

I see that other 12" and even 20" models tend to run at the same speed so maybe I am crazy, but it seems to me as if a lower speed would be nice. Is there a chance that different abrasives would be less prone to burning cherry lumber (I have been using the 12" disks from HF since they are cheap and locally available)? Even if that is the case I still think that a low speed option would be nice.

Adapting an EVS lathe motor and controller would be really nice, but more expensive that I want to spend. Is there some kind of speed controller that would work with the existing motor that wouldn't break the bank?

I might consider taking the sander it apart and seeing how hard it would be to convert it from direct drive to belt drive and using a stepped pulley setup.

[Bill Dufour]

Use a three phase motor and a VFD to control speed. The center speed is lower then the rim.
Bill D.

[Zachary Hoyt]

My 12" disk sander is part of a Shopsmith, so I have variable speed. I do find that I use a low speed, sometimes as little as 700 RPM, when sanding end grain, or when the sanding disk is getting worn and I want to get the last bit of sanding out of it. I don't know what the higher speed is that I also use, it is shown on the speed control knob but not with a number. The downsides to the Shopsmith are that is has no dust collection ability, and the table doesn't tilt, but for my needs it is very handy. I tend to have more trouble burning when sanding maple than cherry, but it likely depends on the individual board's density or something like that.
Zach

[Matt Day]

Can’t help you with yours but I have a vfd on my 20” and I love being able to slow it down.

[Mark Daily]

Would it be possible to use the HF router motor speed controller?

[Jim Becker]

Would it be possible to use the HF router motor speed controller?
No. Those only work with "universal" motors...the ones that scream. You cannot use them on induction motors.

[Pete Staehling]

Can’t help you with yours but I have a vfd on my 20” and I love being able to slow it down. The VFD solution sounds great, but will undoubtedly cost several times the cost of the sander. It may be worth it though.

If I understand correctly, I'd need to find a three phase motor that fit in place of the original motor or could be adapted to fit and buy an appropriately sized VFD. I may price out the options. I have a feeling sticker shock may set in.

I could use my lathe instead, with a platen and table set up on it, but then I'd have the setup time and it wouldn't be easily available when a project was in the lathe. I guess the set up time could be pretty minimal if it was designed well.

[Bruce Wrenn]

Find a 5/8" shaft, 1750 RPM motor, and add the Shopsmith sanding disk. One word of warning, shaft has to run absolute true - no run out. I have the Delta 3450 RPM and a nicely made (by a machinest) 1725 RPM disk sander. When I got the latter, I needed to up grade motor for more power. Took a couple tries in stash to find a motor that didn't have run out at the shaft. There are many you tube videos of making a disk sander

[Pete Staehling]

Mine is already 1750. I am looking for slower and variable speed would be a nice plus. I am considering keeping the current sander and getting or making a disk (maybe a shopsmith?) to run on my lathe (with a banjo mounted table) to get low/variable speed.

[Mark Daily]

No. Those only work with "universal" motors...the ones that scream. You cannot use them on induction motors.

Rats- thanks Jim.

[Bill Dufour]

You could belt drive the existing motor with any type of 3 phase motor and vfd. A vfd will cost around 100 from the bay. Or use a single phase motor and reduce the speed with the pulley ratios. run one motor at a time for a two speed setup. I have actually seen such a two motor setup on bandsaws.
Bil lD

[Pete Staehling]

You could belt drive the existing motor with any type of 3 phase motor and vfd. A vfd will cost around 100 from the bay. Or use a single phase motor and reduce the speed with the pulley ratios. run one motor at a time for a two speed setup. I have actually seen such a two motor setup on bandsaws.
Bil lD

I like the two motor idea. I'll have to look at the sander to see is there is access to some portion of shaft that would allow adding a pulley. I am not sure there is, but if so it seems like something that I might be able to cobble together fairly inexpensively.

[Bill Dufour]

I suppose you could belt drive or wheel drive the rim of the sanding disk.
Bill D.

[Pete Staehling]

I suppose you could belt drive or wheel drive the rim of the sanding disk.
Bill D.
Upon checking it looks like a very easy setup. There is a little plastic impeller that would have to move or go, but I think I can manage to get a pulley on and save it by narrowing the hub of the impeller and moving it more inboard on the shaft. Belt access from below is wide open.

Honestly the placement of the impeller and the air shroud look like it does pretty much nothing to cool the motor. So if it was to need to come off I don't think I'd worry. I could add a muffin fan, but don't think I'd bother unless the motor seemed to run particularly warm.

I'll have to start shopping/scrounging for a motor, belt, pulleys, and other incidental parts. I am excited about this solution.

Harbor Freight claims that it is 1-1/4 hp in the current configuration. I figure that it is really comparable to a smaller motor. Also since I will be effectively "gearing down" with the pulleys I figure less hp will suffice. Do you think 1/2 hp will do the job running the disk at half or one quarter the normal rpm? Or will it take more to get all that iron started going?

[Tom Bender]

1. The 2 motor solution is interesting but to run the faster motor you need to take off the belt or you will overspeed the slower motor.

2. A VFD will only give you about 50% turndown so figure on that.

3. The disk in the lathe is a good approach but don't follow my method. I made a wooden disk which changes shape with the weather.

[Pete Staehling]

I went ahead and made a 12" disk to run on the lathe. I still have to make a table for it. I figure one that mounts on the banjo is probably the easiest way to go. I seldom tilt the table on the HF so it probably wont tilt, but it will have a miter slot and miter gauge or at the very least a little sled permanently set at 90 degrees.

I am really impressed with how nicely it sands when you have the ability to control the speed. I am just using the tool rest in lieu of a table at this point. That is less than ideal, but it is good enough to get a feel for how the disk works at low speed. You can completely eliminate any burning and have much more easily controllable sanding for precise work.

I don't know why more sanders don't come with speed controls. Sure there would be a price hit, but a VFD option would be worth it IMO. As it is, I will live with the higher speed HF model and use the lathe for low speed sanding.

[Darcy Warner]

Be cheaper to buy a 16" 3phase sander and buy a 200.00 vfd than screw around with what you have.

[Larry Frank]

I love the flexibility of my Shopsmith for all kinds of sanding things and my 12" disk sander.

[Pete Staehling]

I love the flexibility of my Shopsmith for all kinds of sanding things and my 12" disk sander.
I hope that the lathe setup will add some of that same flexibility for me.


Be cheaper to buy a 16" 3phase sander and buy a 200.00 vfd than screw around with what you have.
I can see how you might say better, but cheaper? Not sure how it can be cheaper since I am spending essentially nothing on what I have now and am retired and only doing business as a hobby now so am not really losing business productivity.

As far as finding one for $200... I assume that would have to be used. They seldom come up used here. I don't recall seeing one come up locally and even if I branch out to distant locations the prices I see are much higher with most in the $750-1500 range. Maybe once in a while one shows up at $500. I have not seen one for $200 and doubt I am likely to especially locally.

If I was willing to go through the hassle and expense a three phase motor and vfd for my existing sander would be doable for a few hundred for new stuff.

A 16" disk sander with a vfd would be nice but pretty gross overkill for my work since most of it is building travel sized dulcimers. A 12" is already luxuriously large.

[Darcy Warner]

200 for vfd.

[Pete Staehling]

Just a quick update...
I made a table and a little sled for the lathe mounted disk that is essentially a miter gauge fixed at 90 degrees. I have used it a little to shape some tiny parts (bridges and nuts for dulcimers) and some larger parts and am delighted with it. It works with my existing jigs just fine only much better than with the high speed grinder.

The table is mounted on the rails of the lathe and attaches and removes very quickly. The top of the table is cut from an aluminum table from an abandoned router table that already had a miter slot. The support for it is essentially a plywood box.

The disk part is plywood and has a plywood backer plate with an aluminum ring that quickly mounts it on the lathe chuck. The whole thing can come on and off the lathe in seconds.

Running at a little under 500 rpm it is a joy to use. No burning and much more control for detailed precise work.

[Mike Henderson]

Just a quick update...
I made a table and a little sled for the lathe mounted disk that is essentially a miter gauge fixed at 90 degrees. I have used it a little to shape some tiny parts (bridges and nuts for dulcimers) and some larger parts and am delighted with it. It works with my existing jigs just fine only much better than with the high speed grinder.

The table is mounted on the rails of the lathe and attaches and removes very quickly. The top of the table is cut from an aluminum table from an abandoned router table that already had a miter slot. The support for it is essentially a plywood box.

The disk part is plywood and has a plywood backer plate with an aluminum ring that quickly mounts it on the lathe chuck. The whole thing can come on and off the lathe in seconds.

Running at a little under 500 rpm it is a joy to use. No burning and much more control for detailed precise work.

I did almost the exact same thing. But I haven't used it very much primarily because of the setup and teardown time. It certainly takes me more than "seconds" to set up - heck, even getting the stuff out of storage takes a fair amount of time. If I had it set up all the time I'm sure I'd use it more but I can't tie up my lathe with that.

If I had the room, I'd get a dedicated machine, maybe a 3-phase and then add a VFD.

Mike

[Pete Staehling]

200 for vfd.
Yeah, my bad. Even more reason to say there would be nothing cheaper about a 16" sander and vfd. It would be a pretty big investment and pretty gross overkill for my tiny shop and small work pieces.

[Pete Staehling]

I did almost the exact same thing. But I haven't used it very much primarily because of the setup and teardown time. It certainly takes me more than "seconds" to set up - heck, even getting the stuff out of storage takes a fair amount of time. If I had it set up all the time I'm sure I'd use it more but I can't tie up my lathe with that.
I hope it will work out better for me, but time will tell. I have the two components on a shelf above the lathe. If the chuck is on the lathe it takes 30 seconds to install both pieces. It would become more of an issue if there were a project chucked up in the lathe and i probably would tough it out on the high speed stand alone sander at that point, but the good news is that when working on a lathe project I typically stay with it until completion and leave the lutherie work or woodworking project go until I am done with the lathe project.


If I had the room, I'd get a dedicated machine, maybe a 3-phase and then add a VFD.
I have a dedicated benchtop 12" machine, but it is not 3 phase (are any of the 12" bench tops 3 phase?). If I find that switching modes on the lathe is too much of a pain I may look for a 3 phase motor that fits my bench top and get a vfd. Truth be told the vfd is really overkill imo. I am finding I am happy with just running it at 500 rpm or a little less. So the two motor, two speed solution or a step pulley solution would be just fine and may be doable for less $$$ and I could probably even live with a single speed low speed solution.

[Robert D Evans]

Simple way to make a platform for your wood lathe is to get a piece of 3/4" galvanized pipe with the pipe threads on at least one end. Screw it onto a 3/4" floor flange and screw the floor flange onto a piece of 3/4" plywood. Cut the galvanized pipe to length so the platform centers on the sanding disk. The 3/4" galvanized pipe will fit nicely into your banjo and you can easily position it where ever you need to. Rock solid, and easy to install and remove.

If you can get a pulley on the grinder shaft, you can use a treadmill motor and speed controller to coble something variable speed together. Most of those treadmill motors are 2-4 hp and people use them to make their wood lathes variable speed. Of course the sawdust will eventually destroy the treadmill motor but you can get those things cheap or free off of Craigslist.

Just a few thoughts.

[Pete Staehling]

Simple way to make a platform for your wood lathe is to get a piece of 3/4" galvanized pipe with the pipe threads on at least one end. Screw it onto a 3/4" floor flange and screw the floor flange onto a piece of 3/4" plywood. Cut the galvanized pipe to length so the platform centers on the sanding disk. The 3/4" galvanized pipe will fit nicely into your banjo and you can easily position it where ever you need to. Rock solid, and easy to install and remove.
I considered going that way but had scrap 3/4" plywood on hand and made a box that sat on the rails. A piece that drops between the rails and turns 90 degrees before tightening a wing nut locks it in place. I like that the base is keyed into the gap between the rails so the miter slot in the platform automatically registers at the correct angle to the face of the disk.

I find it is just as quick as the banjo mount that I was going to use. I think I prefer the way I went, but both are good solutions.


If you can get a pulley on the grinder shaft, you can use a treadmill motor and speed controller to coble something variable speed together. Most of those treadmill motors are 2-4 hp and people use them to make their wood lathes variable speed. Of course the sawdust will eventually destroy the treadmill motor but you can get those things cheap or free off of Craigslist.
I assume you are talking about the dedicated grinder here. I may do just that if I run across a free treadmill, but after using the lathe as a sander a while I am not really finding variable speed to be a big deal so much as just low speed. I would be pretty happy with a single low speed of 500 rpm especially if the grinder also could be used in it's original configuration. So I may just use a speed reduction in the pulleys and a single speed motor when/if i get around to it. I am less motivated to get to it now that I have the lathe set up working.