Shop-Made Drum Sander

How It Works

This machine is very simple. A plywood box holds a spinning drum that’s wrapped with a long roll of hook-and-loop sandpaper. Unlike a self-feeding commercial drum sander, you manually push the wood against the rotation of the drum. The drum is belt-driven by a small motor mounted to a hinged board. The motor’s weight tensions the belt, just like a contractor’s saw. That’s it. 

The whole sander weighs only 37 lbs., so it’s very portable. It’s compact enough to slide right under a bench.

The critical parts of this machine come in a kit (Photo 1, below). When we first saw the ad for this build-it-yourself sander we honestly didn’t think it would work. In the spirit of adventure, we ordered the hardware. 

When we built the machine, we were amazed at how quickly and easily it took off saw marks and planing marks, just like a commercial drum sander. It’s very quiet, too, and virtually dust-free when hooked up to any dust collector.

What It Can and Can’t Do

This sander will make a smooth, flat surface faster than a random-orbit sander and is less likely to gouge than a belt sander. It works best on short, individual pieces of wood. 

It’s unlikely that this machine will completely replace the random-orbit used motor. (A new motor costs about $100.) The motor must be at least 1/3 hp, rotate at 1,750 rpm and have a 1/2-in.-dia. shaft. The sander’s case is designed to hold a motor that’s less than 7-in. tall and 10-in. long, including the shaft. If your motor is larger, you’ll have to modify the case’s dimensions to hold it.

The case takes less than one-half of a sheet of 3/4-in. plywood. Almost any kind will do, as long as it’s reasonably flat. We used birch plywood. You’ll also need a small amount of 1-1/8-in.-thick hardwood.

Sand surfaces flat and smooth in no time. The sanding drum is 18-in. wide, but this machine works best with boards that are less than 12-in. wide and 24-in. long. It’s very effective for drawers and boxes, too.

Changing sanding grits is easy. Just open the hinged lid, peel off a roll of reusable hook-and-loop paper and wrap a new grit. 

The Sanding-Drum Frame

1. Assemble the sanding drum, bearings and pulley according to the kit’s instructions.

2. Cut the hardwood parts of the sanding drum frame (A and B) to size. Glue and screw together the frame (Photo 2). Measure the diagonals to check it for square.

3. Center the sanding drum on the frame (Photo 3). Mark and drill holes for 1/4-in.-dia. carriage bolts.

4. Recess the heads of the carriage bolts on the pulley end of the frame by enlarging the holes with a 3/4-in. bit (Fig. B).

The Case

1. Cut the plywood for the case components (C through J). Cut the motor opening into the case sides (C) with a jigsaw or handsaw (Fig. A).

2. Screw and glue the case sides to the frame rails (B, Photo 4).

3. Drill or cut a 2-1/4-in. hole in one end (D) for a vacuum hose.

4. Screw and glue the case ends to the case sides and drum frame.

5. Bolt the sanding drum to its frame.

6. Screw and glue the dust ledge (E) to the case sides and the end of the frame. Screw and glue the compartment wall (F) to the case sides. Screw and glue the bottom (G) to the case.

The Top 

1. Create a recess in the bottom of the battens (L, M) with a belt sander or a drill-press sanding drum (Photo 5 and Fig. D). Sand to a depth of 1/8 in.

2. Cut both beds (K) with a 45-degree angle on one edge of each piece (Fig. A). Slightly round over the beveled edges with sandpaper. 

3. Screw and glue the battens to the beds (Fig. A). Keep the ends of the battens flush with the edges of the beds to provide the correct spacing between the 45-degree bevels.

4. Cut fillers (N) to fit in the beveled openings at the ends of the top (Fig. A). Glue the fillers. 

5. Glue the lid cleats (P) to the underside of the beds (Fig. C), completing the top.

The Motor

1. Wire a 10-in. cord (with plug) onto the motor. The rotation of the motor must be counterclockwise when you’re facing the shaft.

2. Bolt the motor to the plywood base (H). Screw two hinges to the bottom of the base (Fig. B).

3. Align the motor and sanding-head pulleys by eye (Photo 6). When they’re aligned, screw the hinges to the case bottom (G).

Final Assembly and Alignment 

1. Screw and glue the pulley guards (J) to the case end (D).

2. Align the top on the case (Photo 7). Screw the continuous hinge to the top and the case. 

3. Predrill and screw in the table-height-adjustment screws. Set the table height (Photos 8 and 9).

4. Screw a hook into the bottom of the top and a screw eye into the case side (Fig. B). Use this to latch the top.

5. Mount the switch to the case (Photo 10) and plug the motor into the switch.

6. Sand and seal all the surfaces. We finished our sander with Danish oil.

Photo 1: Order this hardware kit before you begin building. It costs $115 and contains all the major parts of the sander, excluding the switch, motor and handles.

Photo 2: Assemble a hardwood frame to hold the sanding drum. Screw and glue together the corners. Make sure the frame is square.

Photo 3: Locate the bearings for the sanding drum on the center of the frame. Mark and drill 1/4-in.-dia. bolt holes. The holes in the bearing are elongated so you can fine-tune the drum’s position later.

Photo 4: Screw and glue the plywood sides to the frame to begin building the case. Then add the ends. The entire box is held together with simple butt joints.

Photo 5: Recess the undersides of the battens that span the top to make room for the sanding drum. You’ll have to go about 1/8-in. deep.

Photo 6: Align the motor pulley so it’s directly underneath the drum pulley. Lock the motor in place by fastening the hinges attached to the motor’s plywood base plate.

Photo 7: Position the top to align with the sides. The sanding drum should be parallel to the opening in the top. If it isn’t, loosen the bolts that hold the bearings and reposition the drum. Attach a continuous hinge to connect the top to the base.

Photo 8: Check the height of the table. With 80-grit paper wrapped around the drum, the table should be lower than the drum by the thickness of one playing card. Check all the way across. 

Photo 9: Fine-tune the height of the table by turning adjustment screws. You only need to make this adjustment once, not every time you change grits. You’ll automatically take off less wood with finer paper.

Photo 10: Install a switch with a horsepower rating at least as big as the motor. The switch above ($37, see Sources, page 100) doesn’t need to be wired and is easy to turn off.

Oops!

My golf game is pretty good, but I still make a divot once in a while! I managed to make one with this sander by going too slow and pushing down too hard. Here’s the right technique: Keep your board moving at a slow but steady pace. If you do make a “divot” like the one shown, you can remove it by sanding at an angle to the drum.