I'm building a 20" disk sander. Its a simple enough machine, so I figure I can swing it.
Inspiration: An old school disk sander made by Oliver, a company known for building very heavy woodworking machines.
Wadkin 20" disk-blt sander combo machine.
A common form has emerged among 20" disk sanders sold today. Here are examples from Powermatic, General, and Kalamazoo. Prices range from $1500-$3000 depending on the manufacturer. Certain components differ between brands, but they all function very similarly. Used sanders retain value pretty well, so expect to pay $1000 for Ebay or CL finds. Manufacturers of 20" disk sanders include Apex, Baileigh, Conquest, Dayton, General, Jet, Kalamazoo, Laguna, Master, Oliver, Powermatic, State, Wadkin, Woodtek, Yates. Nearly all run on 220v power.
Option A: Treadmill motor - DC, 220v, 21 amps, 2 hp continuous rated
Now for a motor. Here's a DC motor out of a treadmill. Treadmills are abundant on CL, many for well under $100. But this particular motor isn't going to do it.
Here's an AC motor. Its a 2hp, 3 phase, 115v AC motor I salvaged from a Lifestride TR9100 treadmill. Its got a study bracket, a nice shaft collar, and a heavy flywheel. Three phases permits variable speed control, but because it is configured for 115v power, so it won't work either.
The problem with this motor. Its 115v 3 phase - that's weird. Most small 3 phase motors are 220v. The fact that this one is 110v makes using an off-the-shelf VFD motor control (i.e., TECO FM50) nearly impossible.
I kept the motor controller (Emerson #271101 Rev-E EE110009). I suspect the salvaged motor is going to be a problem, so I posted some questions to the Woodworking Machines forum on Practical Machinist. They told me not to waste my time on it.
This is what the unit looked like originally. The weight of the treadmill was 340 lbs. I literally could not pick up the front end. So, I dismantled the entire thing on the floor of the seller's garage over the course of one hour (super nice people) then loaded the various parts and pieces into the truck. There's a lot going on inside a treadmill. Three circuit boards, a linear actuator, a big motor, 2 beefy steel rollers, a slick-sided platen, a vacuum system, tons of wiring, welded steel chassis, several wheels, heavy rubber bumpers, and about 5 lbs of fasteners. Every part of the unit was heavily built.
10 minutes into the tear down.
60 minutes into the tear down.
A third motor option: 220v, 3-phase that runs at 1725 rpm @ 60 Hz. If I pair this with a VFD, I should be set.
A TECO FM50 variable frequency drive (VFD) allows you to run a 3 phase, 220v motor from 110v power and vary the rotation speed, ramp up/ramp down time, and a bunch of other stuff for a reasonable price. Mine just arrived.
Starting the build. I had a bunch of 5/8" T-111 and 1-1/8" Sturdifloor scraps leftover from my garage build, so they were put to use here.
Sturdy base. The hollow box at the bottom will be filled with lead shot when complete.
Dust chute assembly. The two little ears will make it easy to remove it from the table.
Dust chute mounts snugly to the table between two rails.
A sander-shaped object. I added about a foot more height to the support column. The table now stands at 40" off the floor. The cardboard disk helps with visualization.
Bending form for the bent laminated safety shroud that will cover enclose the disk.
Gluing up the shroud. Three 1/8" strips form the bent lamination clamped around my simple form.
Laminated shroud with a 1/2" plywood backer attached. Once the motor is in positions, I'll attach cut a slot for the motor shaft and affix the shroud to the table with a piano hinge. I want the shroud to tilt back out of the way a little bit for easier paper changing.
I ordered a 20-1/4" OD, 5/8" ID donut of 1/4" aluminum plate from Alaska Steel. They fabricated this with a plasma cutter, so neither the rim nor the center hole were very smooth. The rim was easy to clean up, but the hole was not bored cleanly. Might have been better off having them simply add a dead-center punch mark and drill the hole myself. Spinning the disk on a sandpaper-wrapped dowel helped to clean up the hole. In the end, I likely will not use the center hole. Instead, a flanged shaft collar with countersunk bolts may work better.
Flanged shaft collar. Attaching the motor to the disk platen requires some sort of coupler. I looked for options using these search terms: "hub shaft collar coupling", "sd bushing", "qd bushing", "shaft collar mount". A gokart wheel hub that fits a 5/8" keyed motor shaft might also work. A shop-made plywood/melamine hub may or may not be flat enough to run true.
A good way (?) to support an MDF/plywood/melamine platen: two thrust bearings mounted on either side of the disk. From someone on YouTube.
Disk Sander Homemade - 20" by From the Wood
Make a Disk Sander by John Heisz
Homemade 22" Disk Sander by Jords Workshop
12" DIY Disk Sander by D. Comeau Custom Knives
Tool Reviews: Teco FM50 Variable Frequency Drive by briancnc
DC Treadmill Motor Controller Explained - Belt Grinder by MikeManMade