12" Disc Sander




Introduction: 12" Disc Sander

About: I have been a woodworker for over 40 years, working in a cabinet shop to making custom interiors for executive jets. I have a full shop in my garage and have been making wood pens for the past 3 years. I am ...

This is a shop built 12" Disc Sander

Step 1: Motor Mount

As I wanted to use an old motor that I have had since the 70's, I needed a way to mount the motor to the 3/4" x 12" round disc. I found out that shopsmith used a motor mount to 1" thread for the lathe motor connection. With this and a 1" thread face plate I was in business.
I took a 3/4" birch plywood and marked the center with lines perpendicular to one another. I then marked a 12 1/4" circle and cut it on a bandsaw using a circle jig I also made. I left 1/4" on the diameter as I knew when I mounted it to the motor it would not be true.
I take care of this in the next step

Step 2: Trimming the 12" Disc to Size and True to the Motor

In this step I mounted the motor on my workbench near my vice. I used the 3/4" threaded rod that I purchased for the table mount to hold my lathe tool rest. With the 12 plate mounted to the motor I marked the disc at 12"
I then turned on the motor and cut the disc to size using my lathe tools.
Note that I made a box with base from 3/4" plywood assuring the Disc would be tall enough to clear the 3/4" threaded rod for the table.

Step 3: Balancing the Disc

Even though I cut the disc mounted on the motor I noticed I had excessive vibration when running the motor.
So I mounted the motor to the table, and spun the disc by hand, marking the top back of the disc once it stopped spinning. I did this 6 to 10 times and taped a washer on the back of the disc near the marks as these showed the disc section that was the lightest. I.e. The heavy part of the disc will stop at the bottom more than not..
I then turned on the motor and still had vibration, but less than the initial test. I repeated the above tests, adding one more washer. I then moved these washers toward the center of the disc and checked vibration. Once I was happy I epoxied the washers on and attached the sanding disc and checked vibration again. Zero vibration... I could run the motor with disc on my bench with no movement.

Step 4: Sander Table Mount and Back of Sanding Disc Shield

I had a Delta sander that I used the table off of. I put a 3/4" threaded rod through the middle of the box as seen in the first 2 photos.
I also cut a 12 1/2" disc and made a wood shield to cover the disc. I then painted the box and back shield.

Step 5: Adding Dust Collection

I used a 1 1/2" PVC Pipe and a wood adapter to make the dust collector and attached to the disc shield.

Step 6: Adding the Table to the 3/4" Shaft

I mounted the Delta Table to the 3/4" threaded rod.
I created a larger table to mount on top covering the entire 12" disc.

Step 7: Adding the Switch

I used an old Craftsman switch added to the sander to turn the motor on and off. I mounted the switch on the side of the sander behind the disc shield for safety.

Step 8: Finished Sander

This is the finished sander that is solid... I found a damaged Delta sander for $64 so I bought it and sold this sander for $120. The guy that purchased it stated he would buy it if he could not stop the motor sanding a 2x4... Sander did not stop..
I now have a Jet 12" that was damaged for $146... $600 sander and just minor repairs needed...

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Runner Up in the
Build a Tool Contest 2017



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    32 Discussions


    1 year ago

    Excellent work, I will build one for my hobby.

    You are a genius and have just given me a project for next weekend. I too have had a 1/3HP motor collecting dust for years. I think I have everything I need to build it.

    3 replies

    Just cheap... :) good luck and spend the time getting it balanced... Before I started the project I read that you need a 1 hp min.. Not the case.. Could not stop the motor when sanding.. Looking forward to seeing the results..

    No, no. It's not cheap. It's called frugal... and we're very frugal in our household.




    1 reply

    Thank you... My dad was one that said if you want a new bike, take it apart, sand and paint it... New bike.. I did that 5 times when growing up.. Not afraid to tackle anything

    God bless you for adding the dust collection to this build. This can help avoid the serious problem which most don't think about, dust explosions. Depending on what the dust is from, you can have quite a problem when a dust explosion occurs. (If you doubt this take a 1/2 teaspoon of powdered sugar out to your campfire and throw it at the fire from a good distance. It WILL explode violently.) The Dixie Crystals Sugar plant had an explosion some time ago, ruined the plant. Almost 3/4 of it had to be rebuilt from scratch. It is iron filings or wood,it can be almost as destructive. I wear a breather in addition, because you can repair lungs esily....

    1 reply

    I worked in a cabinet shop in high school and we had a dust explosion in an outside dust collector that was not grounded. This was back before you were required to put grounding straps on the duct collection tubes. Velocity in the pipe is like socks on carpet in winter. You build up a nice shock.

    Great build and the "balancing act" is brilliant. You must have sen a number of tires mounted and balanced to old school way. Definitely voted you up!

    1 reply

    Thank you.. I was ready to dump the Sander with the vibration. Was shocked that the wood would be unbalanced. But as an engineer I remembered my dynamics teacher talking about how a fly landing in a record player (Very Old School) cause the needle to jump as it would throw it out of balance. I spend a lot of time getting it balanced, but when done I could run the motor unclamped on the bench with no movement.

    I'm with Prfesser. 1000%. Very nicely done. I don't even bother with the video only "NOT-ibles" either.

    1 reply

    Thank you.. I have a Tablesaw Outfeed table where I added video but based around the build just to show the linkage. Otherwise videos are for you tube and most are not very clear.. Agree with you

    This is about as good a sander as is possible. Trying to tweak is nearly impossible. But, maybe t nuts for the faceplate and MDO for the disc. That said these are minor and the Instructable is great. Very well done.

    1 reply

    Thank you.. I ended up buying a ShopSmith 12" Disc that is metal and a bit heavier and it slipped right on the motor. Plus it was $20 on eBay


    1 year ago

    Interesting build. I have that exact same switch that I just yesterday took off the table saw and installed a 220 switch on it and rewired the motor for 220. I realize balancing the disk is important. And that might have been a lot easier using 3/4" MFD instead of plywood. MDF is solid and once cut it finises off amazing well. Nice project. does 1725 RPMs seem fast enough? IDK.

    2 replies

    The Jet Sander that I have now is 1720 max RPM. So no issue on speed. MDF is a good idea and heavier which is good for the disc. Just wonder with the torque on the motor would want to cause the screws on the face plate to come loose.

    One option for securing the disk might be to use a larger face plate with more screws.