Disc sander speed please

[Tom Bussey]

What is a good RPM for a 12 inch disc sander? I know a lot of sanders are direct drive to a motor. I have never checked but I assume they are of the 1725 RPN verity. I know that Shop Smith has a a variable speed system and there is a range in that system.

More information, I have a 9 inch disc sander attached to my 1 x42 belt sander and and one attached to my 4 x 36 sander And since they are attached directly to a motor, the rime speed would be a lot slower than the rime speed of a 12 inch disk. I also have a 12 inch that the disc is attach directly to the motor. It is reversible and I like that feature. But it is a pain to have to pull the entire table to change the paper ( cloth ) discs. Also for me the tables are very small and I find it hard to support larger pieces

I hadn't planned on posting this at the present, so I don't have the exact information but, I have a reversible motor off from an old Delta shaper. It is a small motor and I am guessing it is a 3450 motor 1 HP or smaller. I have a 2 inch pully on the shaft that supports the Discs and I am looking for an optional speed so I can get pullies for the build.

I can go to my machinery Hand Book to calculate the pully sizes I need.

But if someone knows the optional speed and pully sizes it would be greatly appreciated.

My shaft is a precision ground 5/8 shaft and it fits the bearings perfectly but the Shop Smith discs I purchased will not go on , size for size doesn't work. I will take it to work tomorrow and emery paper the shaft diameter down so the disc will go on. Then I will post pictures of what I have to date and get the motor information also.

Thanks for your help in advance.

[Tom Bussey]

I had time to go over to the shop after I posted. The motor is a 3/4 HP 1725 RPM motor. and I checked my 12 inch disc sander and it is a 1725 RPM motor.

I guess I have been thinking about this build for a couple of years and have been collecting parts. It seems I have been here before because I have a 2 inch pully already on the motor and a 2 inch pully on the shaft so I am at 1725 for a speed. Which is the same speed as my commercially made disc sander runs at. It is called getting back to an unfinished project. I am sure that none of you have any of those.

I have some other engineering ( research and development ) things going on so I will post some pictures as when I get my shaft and disc to fit tomorrow.

Who knows maybe I will give someone else an idea.

[glenn bradley]

I have two 12" discs because they came attached to the spindle and vertical belt sanders I have. Both are 1725 RPM. I gave my 3450 RPM 12" disc away as it was too fast for my use. Your optimal speed will depend on your use. If you use a 60 grit disc and primarily just remove material a faster speed will do that job faster. If you want to do things like fine tune miters or shape parts a slower speed may serve you better. I used to subscribe to the argument that you just had to use a little finesse with the faster speeds but got tired of having to use my technique to override what was not the right tool for what I was doing. YYMV.

[Steve Jenkins]

I have a Jet 20” disc direct drive. The motor says 1720 rpm

[Zachary Hoyt]

I have a ShopSmith and depending what I am doing I often run it at 700 or so RPM, the lowest speed, or sometimes a bit faster, maybe up to 1725 at times. I use only 120 and 80 grit discs and have one for each grit so I can switch very quickly. Especially for sanding hardwood end grain or sanding brass the low speed is nice, but it's too slow for some jobs.

[Steven O Smith]

If you can make a DC motor work, treadmills can be had cheap to free, largely because people don't know to lubricate the belt. Then you have your choice of RPM.

[Tom Bussey]

I have a 3/4 HP reversible motor already. I like having reverse, Lets say you want to do a 1 inch radius on each end of the board. One doesn't have to layout the radius on one side and then turn it around and layout other end. In this case one could just switch discs. But I am leaning on each disc having a different grit.

I got it together for the first time this afternoon and the spacing was 8 or 9 inches apart. I think that than is a little to wide so I will cut 3/4 of an inch on both ends and then recut the whistle notch.

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Then I checked for center line height to base to see where it came to. The table is about 7/8THS below the center line on the purchased disc sander I have and this new one is about 1 1/8th . From what I can see the 1/4 inch won't make much if any different
to the sanding operation. 99% of all sanding that I do is at 90% so I am not planning on making the table to be able to be put at an angle. I am not sure if I will keep the table as it is or turn it 90 %. I have some other things to consider also. I am a research and development stage right now. The top is Corian.

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Anyway that is where I am to date.

[Bill Dufour]

VFD+ three phase 1725 motor.
BilLD

[Tom Bussey]

I already have a motor and I fail to see what value a different motor would achieve in cost verses actual use.