Homemade 1"x42" belt sander (strip sander)This article also available in Spanish
I bought this 1"x30" strip sander at at Canadian Tire a few years ago, and it's quite handy. but ther are a few things about it that I don't like. When sanding larger workpieces, I often hit the back of the sander. Also, I can never seem to get the belt to track on the center of the platen, and it runs too fast. So I thought I'd try to build a better one.
What got me started was a successful experiment at flattening the outside of an inline roller skate wheel on the table saw. Flattened, they could be the wheels for a strip sander. I figured this would be a quickie project.
But then I started thinking about various aspects of the design - how to adjust tracking, how to adjust tension, etc.
To work it out, I drew a rough CAD model, which then became increasingly detailed. I then printed out the parts 1:1 for cutting out on the bandsaw from the cad model using my BigPrint program.
I have to say, even if I had a CNC machine, I'd still cut them on the bandsaw. I can make better use of existing scrap, put the parts closer together, and the bandsaw literally cuts 18 mm plywood ten times faster than a hobby CNC machine would.
I cut the rectangular parts on the table saw without gluing on the templates. For simple rectangular parts, it's easier to transfer the measurements than to glue on a template and peeling it off later.
I checked that I have the right parts of the right size by laying them on the template.
There are a few slots that need to be cut. I cut these by making a series of holes with a brad point bit, then drilling between the holes. You could also use a scroll saw. jig saw — or a slot mortiser for these.
I clamped it in place, then drilled the pilot hole through both pieces to get the holes perfectly aligned.
A piece of plywood goes on the back to hold it steady. Aligning that and screwing through both pieces would have been too difficult, so I accurately laid out the pattern of holes on both pieces, drilled pilot holes, then used those holes to align it as I screwed it together.
I used some extra pieces of plywood as spacers to jig things up for where the holes need to go to leave the two thicknesses of space for the plywood.
I have to say, it's much more evident how I do this in the build video.
Two parts of the frame need to extend forward by the same amount. I'm using part of the frame, clamped on to the larger piece as a spacer to line as I drill the pilot hole for screwing another piece on. This is more clear in the build video.
Upper wheel mountThe upper wheel mount is tricky to make because the sides of it need to be precisely aligned and screwed together.
I'm using a scrap that is the same width as the upper wheel mount, plus two pieces of paper to space them the right distance apart to fit around the wheel mount arm later. I check several times to make sure these are lined up correctly as I clamp them.
I then put screws in these two pilot holes to keep things aligned. and drill the rest of the pilot holes
After that I expand the pilot holes in the upper wheel mount back to clear the screw's threads, and add countersinks for the screw heads.
In the end, I still had to make adjustments to the alignment, using a file to slightly expand the notch that the shaft for the upper idler rests in.
Idler wheelsI rigged up a temporary circle cutting jig to cut away the outermost part of the roller skate wheel on the bandsaw. I could skip this step, but I'm afraid there might be some sand grains embedded in the rubber, so I cut away the outer-most layer with a bandsaw.
After that, I shaped a crown onto the wheel buy raising the blade slightly and pushing the wheel slightly into the blade (not all the way on) to cut a bevel on one side. After that I flip the wheel around and cut the bevel on the other side.
Drive wheel and pulley
The drive wheel needs to be fixed to the drive shaft. It's easier to make it out of plywood than to adapt a roller skate wheel for the job. I glued a 18 mm thick piece and a 6 mm thick piece to form a 24 mm thick blank (ideally, this blank would have been slightly thicker)
I'm using an 8 mm thick shaft for the drive shaft, but you could use a thicker shaft too, so long as you have bearings that accurately fit the shaft. You could also use a bronze bushing or a piece of oil soaked maple as a bearing block for the shaft. Wooden bearings last surprisingly long.
I roughened up one end of this shaft with the coarse wheel on the bench grinder. I also add a chamfer to the end of the shaft.
I used the same procedure to shape a crown onto the drive wheel. But instead of flipping the wheel over to cut the other side of the crown, I move it beyond the center of the table saw blade to cut the bevel on the shaft-side of the drive wheel.
You may be thinking "use a lathe", but it would be very difficult to mount the wheel sufficiently centered. By spinning the wheel on its own shaft, I can ensure that the outside of the wheel is exactly concentric with the shaft. Even if the wheel was mounted with a slight wobble, after trimming it on the table saw, the edge of the wheel would still be accurate.
I drilled a hole with a tight fit for the shaft, but not so tight that I couldn't pull the shaft out by hand. I filed a notch in one side of the hole and ground a groove in the end of another 8 mm diameter shaft with an angle grinder.
With the shaft inserted and the pulley and shaft notches lined up, I drove a small finishing nail into the space to act as a "key".
Next I cut the V-belt groove on the table saw. I made a block with a V-notch to rest on my table saw sled so I could position the pulley precisely without getting my fingers near the action. This worked well, but I need the sides of the slots to be angled for the V-belt.
I didn't run into any problems, but let me warn you that this is not a particularly safe operation. Keep your hands away from the blade. And be sure to spin the shaft with a drill, not by hand! And use a table saw sled.
I then put my block and drill on the other side of the blade to cut the other bevel. I also reversed the drill so I wouldn't be making a climb cut.
I could have done this by flipping the pulley on the shaft, but moving to the other side was easier.
The shaft is clamped between two pieces of hard wood, and I'm actually using that wood to help guide the angle grinder wheel.
The end of the shaft has a flat spot from its previous application. I cut that part off later.
Mounting the drive shaft
Before mounting the drive shaft, I had to mount the sander frame to the plywood base. I started by placing it on the base, marking the outline of it, drilling some holes from the top for where the screws go, and then clamping the frame onto the base.
I then flipped the base over and drilled pilot holes and screwed the frame onto the base from below.
I need to mount the bearing holder for the main drive shaft so that the drive shaft is perpendicular to the main frame. I drew a pencil line on the base and positioned the bearing holder to line up the drive shaft by eye.
In retrospect, I guess I could have just held the square against the shaft and lined it up that way!
Also note the bearing, which is barely visible. A screw just above the bearing keeps it from popping out of the hole.
Now attaching the pulley to the end of the shaft. I used a small #4 screw as a "key" to make it easier to get it out again if needed.
I also need to prevent the lower idler pulley from moving left and right. I made some spacers out of 1/4" (6 mm) Baltic birch plywood with holes a little too small, then put one on either side of the pulley (I had to pound the shaft with a hammer to slide the spacers along). Make sure the pulley isn't squeezed between the two spacers.