Benchtop Disc Sander

Disc sanders are extremely useful tools used for rough shaping wood. When I needed a dedicated sander that could take off a lot of material at once, I was less than impressed with what was available. After not finding any disc sanders with the size and power I wanted in my price range, I started thinking of other options. Looking at what others have made in the past, most did not include a tilting work surface. This was a great design challenge that turned out better than I could have hoped!

If you are looking for your own disc sander and not impressed with anything available for the price, a homemade disc sander may be for you.

This is a comprehensive list of tools and materials I used. Not everything is necessary, but I'm sure you will find them useful.

Tools:

• Table Saw
• Flat Tooth Saw Blade
• Band Saw
• Awl (used for added accuracy)
• Forstner Bits (varying sizes)
• Sanding Blocks
• Dial Indicator
• Box Cutter
• Pair of Compasses
• Drill
• Router and Bits
• Circle Cutting Jig (bandsaw)
• Various Clamps
• Jig Saw
• Metal Countersink bit
• Angle Grinder
• Protractor
• Dowel and Tenon Center Set
• Vice Grips

Materials:

• Die Cast Hub 3 3/4 x 1/2 inch bore
• T-Handle Hex Wrench
• Power Switch
• Large Gauge Extension Cord (used as power cord)
• Melamine
• Sand Paper
• Plywood
• T-nuts and bolts (varying sizes)
• New or Used Motor
• Aluminum Can (for shims)
• Glue
• Screws
• Hardwood Scraps
• Dowel Pins
• Wood Filler
• 1/8 inch metal rod
• Chest Latches
• Spray Paint
• Rubber Feet

There are many motors out there that are suitable for a benchtop disc sander. However, free motors are the best motors. If you can find any motor second hand, that would be best for this project. You want to find a motor that is at least 1/2 HP (3/4 HP or 1HP would be best). The motor that I used, was from an old swamp cooler. It's rated at 3/4 HP with two speeds, 1725 RPM and 1140 RPM. Most 12 inch commercial disc sanders (that I looked at) are somewhere between 1600 and 1800 RPM making my motor perfect!

Make sure that you know what way your motor spins before making this project. Most motors are reversible, but not all. The motor I used runs clockwise (backwards from most, if not all disc sanders). I could have taken the time to see if my motor was reversible, but I didn't care. Just be sure to always use the 'downstroke' of the disc when in use to keep all your fingers where they should be. If your motor does not spin clockwise, you will want to move the dust collection port to the other side of the housing.

I have outlined the steps I took when making this sander, but your's will most likely be different as every motor mounts differently. I have added rough measurements to the end of each step to help with making your own sander.

Using a piece of 3/4 inch melamine particle board, draw a circle the size of your sand paper. Cut the disc just larger than what was drawn using a bandsaw or jigsaw. Find the middle of the disc and mark screw locations to attach the disc to the hub. Cut shallow holes at the screw locations using a forstner bit to create a recess for the t-nuts. Attach the hub to the disc and cut off the extra length of bolt.

Having never created a tool before, I was a bit weary of the stability of my simple design thus far. I clamped it to my workbench to do preliminary tests and to get ready to shape the disc. I made temporary supports out of scrap 2x6 I had laying around the shop.

Once I was sure nothing was going to explode, I shaped the edge of the disc using my sanding blocks stabilized by a temporary tool rest made from scrap wood.

Using a cut up aluminum can as shim stock and a dial indicator, balance the disc. This is important so your sander has complete contact with the work piece for the whole rotation. If the disc wobbles, you will have uneven wear on your sandpaper. With a lot of tinkering, I was able to get this disc to wobble less than 5 thou.

Using a compass, mark out the size of the motor to be held along with the mount to hold it. Pre-drill the screw holes before cutting the mount apart (this will ensure everything lines up correctly). I used a bandsaw to cut everything apart. Test fit the mounts.

two 10 x 8 inch squares to make both mounts.

Use a scrap piece of wood to line up the front of the sander to ensure clearance. Pre-drill and attach the bottom. Once you have verified the fit, disassemble and glue everything together.

10 x 10 inch square for the bottom.

Use scrap pieces of wood to elevate the sander. This will ensure clearance of the disc above the workbench. Mark the locations of the bottom and motor mounts and decide where you want your screw locations. I secured each side with two screws in each motor mount and three in the bottom of the housing. Once everything is lined up successfully, glue the sides in place.

10 x 11 inch sides.

Find the location of the motor shaft and drill a large hole at it's location (I started with a pilot hole to ensure accuracy. This will allow the hub of the disc to be mounted from the front of this face. Mark, pre-drill, and secure the face using screws (DO NOT GLUE).

14 x 14 inch square.

Using a core box router bit, route a slot deep enough to allow access to the set screw on the disc hub.

Create a top for the sander housing. Using a dado stack or flat tooth saw blade, cut a rabbet on each side to allow the top to sit securely in place.

10 x 11 1/2 inch top.

Using a circle cutting jig, cut a disc just larger than the the main disc. Remove the bottom right hand corner of the guard. This will allow for better dust collection.

14 x 14 inch square.

First attach the front of the enclosure followed by the disc. Using the disc, align the guard to the front and secure it in place with a few screws.

What better way to test out the usefulness of the new sander than to use it to shape itself? Set up a temporary rest and shape the guard to match the front face.

My guard needed a little bit more thickness so I added a 1/4 inch plywood in between the face and the guard. Glue, clamp, and shape once dry as shown in the previous step.

Dust collection on a disc sander is extremely important (this will also aid in keeping the motor cool). I routed out a large section of plywood to keep about 1/4 inch of clearance in front of the disc.The top of this board is placed at exactly half way up the disc. This will help out greatly later on when setting the height of the table.

14 x 7 inch dust collection cover.

I created this dust collection port around the hose to my shop vac. It's shaped to only cover about half the front of the sander while having a 135 degree angle.

Trace the outside of the dust collection port onto the dust collection cover. Mark the interior perimeter and cut using a jigsaw or scroll saw. Glue in place and smooth out the edges using sandpaper to ensure smooth air flow.

Using three long machine screws and t-nuts, attach the dust collection to the disc sander. This will allow for simple removal of the dust collection for easier sandpaper changes.

Using the previously discarded scrap from the centers of the guard, cut in half to create the trunnions.

With a circle jig on the bandsaw, cut the exterior of each trunnion so they match. Cut 3/4 around the half circle in two locations to create a track about a 1/4 inch wide.

Using the scraps from the previous step, fill the end of the gap created in the previous step. Using a round file or same diameter drill bit, round both ends of the track.

Using hardwood, make mounts that fit on each side of the sander. This will hold the trunnions created previously. Dress the edges with whatever router profile you like. Drill recesses in the back anywhere a screw head will prevent the mounts from resting flat against the housing. Drill four clearance holes in each mount and pre-drill the holes in the site of the sander housing. One hole is countersunk because the trunnions will ride directly against that face.

Trace the track of the trunnions on a piece of hardwood and cut them out with a bandsaw. Using sanding blocks, shape them until they slide easily in the track of each trunnion.

Use the index holes created from the circle cutting jig to index the trunnions on the top and middle of each side of the dust collection cover. This will be the point that the trunnions will rotate around even when the get cut down in a later step.

Glue the slides in place. After the slides are dry, mark the edges of the trunnions on the slides and cut just short of this mark. This will allow the knobs to hold the trunnions tight against the mounts and not apply any pressure on the slides.

Since the table will be permanently attached to the trunnions in a later step, it needs to be separable (this will allow easy replacement of the sandpaper.

To create a spline joint, cut the table in half. Using a flat tooth table saw blade cut matching dados to accept a 1/4 inch spline of MDF. Glue the spline on one side only so the table can be separated.

10 x 17 inch table.

Centering the table on the housing, measure what needs to be removed to allow for the clearance of the table. The table needs to reach back to the ends of the trunnions.

Using a tilting bandsaw, a 45 degree cut was made along the inside edge of the table this will allow for the table to be moved down to 45 degrees past square.

Using the flat tooth blade on the table saw, cut a rabbet the size of the trunnions and half way through the table.

I ended up make separate larger round knobs as I didn't like how these turned out, but the method is the same.

Cut a knob in any shape you like. Drill a hole through the center the size of the t-nut and tap the t-nut in place. If you find your t-nut is falling out often, you can use a small drop of epoxy to hold it in place after everything is painted.

This was changed to a regular bolt once the entire project was finished as the wood screws did not hold well enough. But the existing hole was used to epoxy the bolt in place after everything was painted.

I created a switch cover using MDF, but one can be purchased for much less time commitment.

Mark the location of the switch and cut it out using a jigsaw.

Drill a hole in the side of the enclosure the size of your power cord. Do not tie a knot in the cord to use as a cord stay. This can cause shorts and other electrical problems down the road. This was only done as a temporary measure. A cord stay is shown in a later step.

Running the power inside, connect the common to the motor along with the ground, run the hot side to the switch and back to the motor.

Secure the switch in the side of the housing and verify everything works correctly.

Set the table on the trunnions as is and mark the height on the disc. Remove the table and mark the center of the disc. Measure the distance between the center of the disc and the mark of the height of the table. Using a table saw, remove this much from the trunnions. Replace the trunnions back on the slides and the table. The table should now be the same height as the center of the disc.

Mark the height of the bottom of the table and cut the dust collector cover to a 45 degree angle. This will allow the table to tilt down 45 degrees off of square. I had to change the height of the screws holding the dust collector in place. This wasn't a big deal and I was able to fill the holes in a later step before painting. Secure the table to the trunnions using screws (DO NOT GLUE YET).

Use flat head screws to attach the steel to the wooden table. This will give a much more durable work surface as well as hold the two table halves together. Drill a 1/4 inch pilot hole through the steel. Clamp the steel in place and drill the clearance holes through the wood. Using a metal countersink bit, cut the hole in the metal wider until the flat head screw is flat with the surface. Secure on the other side of the table using t-nuts.

17 x 6 1/2 steel plate.

This was one of the most stressful steps as I needed to cut into the table to allow for clearance of the dust collection port while tilting the table down 45 degrees. I cut off little by little until I was able to measure 135 degrees from the disc face to the top of the table. From there, mark what to remove from the steel plate. Using an angle grinder and a small cut off wheel in a rotary tool, remove this section from the steel. Use hand files to smooth the rough cut edges.

This disc sander was designed to have vents in the back utilizing the shopvac as the method to cool the motor. With the shopvac on, air will be drawn from the back the unit through these vents cooling the motor, around the disc collecting all sawdust created, then into the shopvac itself.

This simple design was created using a 3/8 inch drill bit and laid out with a protractor and compass.

11 1/2 x 11 1/2 inch square.

The top and back are held in place using dowel pins along with center finders to drill accompanying holes. The top has two dowels in the front and two in the back. They have drastically different spacing to easily see what way it goes. The back is held in place using six total pins.

Using wood filler, fill all holes and plywood defects. This will make for a much better painting result. Sand when dry.

Use an 1/8 inch rod to hold the back in place. Bend them using vice grips and make these angled hooks.

Drill holes in each side of the back panel large enough for the hooks. I used a 9/64 inch drill bit.

Use simple chest latches to hold the back in place. If your latches have a small tab at the top, remove it with a file. Hold the back firmly in place and mark your screw holes. To ensure that these latches hold tight, drill the pilot holes 1/16 of an inch 'tighter' than previously marked. Once each latch is in place, ensure they hold the back firmly in place.

Decide on what color scheme you like and paint. I opted for a blue/grey color scheme to match my table saw. Using primer first will give a more bold color while covering up most of the wood grain.

There are many commercially available cable stays, but I couldn't find any that was not designed for an electrical box. Since I didn't want to include a box inside my sander I made my own cable stay that functions just the same as anything commercially available for free.

Using some pieces of scrap hardwood, fashon a clamp that will keep the power cord from being pulled from the motor. I used the spindle sander to carve out this small cove.

I had originally planned on using wooden washers between the knobs and trunnions, but I found the undesirable effect of it sticking well to the freshly painted surfaces. Using two or three fender washers allows the knobs to be tightened without anything sticking.

This simple step will protect your paint job more than anything and will keep your sander in place while in use. Just screw them in place and forget about them.

There is plenty of space inside the housing to store the t-handle hex wrench. If you are concerned about it causing troubles with the motor you can make a simple holder for it, but I didn't find this necessary.

Now that your new disc sander is complete, enjoy it! Make something useful with it! I used this tool many times over the past year (when I got distracted by other projects before it was complete). It was extremely useful for these projects (clicking on these images will take you to those projects):

What projects have you made with your disc sander? Have your made your own sander? I want to see them in the comments!