Benchtop Belt Sander Jig

I've got an old Craftsman belt sander and I was looking for a way to increase its functionality. I wanted to be able to easily shape and smooth pieces of wood and maybe even make them square. There are already a few belt sander jigs on Instructables but they weren't exactly what I was looking for. I found this jig through a web search and want to give the design credit to Sandor Nagyszalanczy at http://www.rockler.com/how-to/sanding-jig-belt-san...; this Insturctable is simply the documentaiton of my build based on Nagyszalanczy's design. The key elements to this jig are the table being both perpendicular and parallel to the sander as well as being inclined which "reduces chatter during sanding and distributes wear more evenly across the belt." The rig I came up with to secure the sander works on my sander. Your rig will be somewhat different (unless you happen to have a 40+ year old Craftsman sander like mine) but the general approach I took to secure it should work for you. Let's get building!

I like to build with what I have on hand as much as possible; for this table, all of the wood was left over from other recent projects. All of the hardware (except one bolt and the wood screws) was purchased specifically for this project; the T-nuts and their matching bolts, nuts and washers and the threaded rod and its matching bolts, nuts, and washers.

The List:

1 - piece of plywood for the base of the jig. I had a piece of 9mm ply (a little over 1/3") that was 20" x 14.5" and that worked just fine. You will want the base to be 6 to 8 inches longer than your sander; the width (though somewhat arbitrary) should be at least 8 inches beyond the position of your sander's belt once mounted - basically 8 inches plus the height of your sander.

1 - piece of plywood (or solid wood if you have something wide enough) that is a couple of inches shorter than the base and as wide as your base minus the height of your sander . This ply should be at least 1/2" - I had a piece of 9mm ply that was 16.5" wide and 17.5" long which I cut in half along the width and laminated together with wood glue and clamps to give me a piece almost 3/4" thick by 16.5" long and 8.75" wide which was nice and sturdy - and more importantly very flat - for the table.

2 - pieces of solid wood - I had a 28" piece of 1" x 6" pine on hand. I cut two 9" pieces and then ripped them to the appropriate height with a 12.5 degree angle at the top where the table attaches.

1 - length of 1" by 2" for the sander mounting rig - I used about 20" in total.

7 - 3/8" T - nuts

1 - piece of 3/8" threaded rod - I used about 17"

1 - 3/8" x 4" hex head bolt - you're going to have to cut this bolt down to about 1 7/8". I had a 3" hex head bolt on hand and it was kind of a pain to come up with a safe way to cut it - point being, a longer bolt is easier (and safer) to cut

3 - 5/16" nuts

5 - 5/16" washers

4 - 1.5" wood screws

12 - 1" wood screws

• I used the Max Cut 2 https://www.instructables.com/id/MAX-CUT-2-Circula... for all the wood cuts except one. I *love* this jig, if you haven't checked out the Instructable for this you need to!! And if you have a circular saw you need this jig!
• Battery powered drill/ screwdriver
• Jigsaw - I only used the jigsaw for one cut which could have easily been made with a coping saw
• Large L - square. this is an essential tool for this build
• Framing square, also an essential tool
• Clamps
• 1" spade drill bit (for countersinking the T - nuts)
• 7/8" or 1/2" drill bit for the T-nut sleeve - I did not have a bit large enough for this so used round files to make the holes large enough to accept the T-nut sleeves.
  • round wood files
• Small drill bit for pilot holes
• Flat wood files - to make the knobs
• Tape measure
• Pencil
• Hammer
• 14mm and 17mm open end wrenches

This is going to be a general description of how I went about securing my sander. You will need to make modifications based on the physical properties of your sander.

1. Lay the sander on its side on top of 1" x 2"s that will be cut in shape to hold the sander body. The open side of the belt rollers should be facing up and the top of the sander's body flush with the long edge of the base.
2. Using your long L - square, position the sander so the sander's plate is parallel to the long edge of the base - this doesn't have to be exact but you should get it as close as possible - use a clamp to press the sander against the base and hold it in this position (photo).
3. Mark the 1" x 2" to the shape of the sander (photo).
4. Take this little rig apart and lay the sander - still on its side - directly on the base.
5. Cut out the marked pieces (photos) and fit them against your sander. Be sure to keep the top of the sander's body flush with the long edge of the base and the plate of the sander parallel to the long edge as much as possible.
6. Once you're happy with the position of your blocks and the sander, reclamp the sander to the base making sure nothing moves.
7. Check all the blocks again making sure they are snug against the body of the sander and clamp them in place.
8. With the sander clamped in place, determine where you want to place the threaded rod for the sander clamp and mark the blocks
9. Remove the sander.
10. Trace an outline of the blocks on the base and remove the blocks.
11. Drill pilot holes through the base where you want to place screws to mount the blocks.
    1. If your 3/8" threaded rod is going to be on these blocks be sure your mounting screws are at least 3/4" from the center of the rod to be clear of the T-nut.
12. Now that the blocks are removed, drill a pilot hole for the threaded rod all the way through the block.
13. Now is the time to attach the T-nut to the block.
    1. Turn the blocks over and locate the pilot hole for the threaded rod. Using a 1" spade bit, drill about 1/8" into the blocks (photo) - enough so that the T-nut will not protrude past the bottom of the blocks when the blocks are mounted on the base (photo).
    2. Now drill out the center using the hole made by the point of the spade bit so that the sleeve of the T-nut just fits.
       1. I didn't have a bit this big (I think it is a 7/16" or maybe 1/2") so I used a medium and large round wood rasp to size the hole to accept the T-nut.
    3. Dab a little wood glue or if you have it, epoxy around the ledge of the countersink hole (photo).
    4. Using a hammer, carefully drive the T-nut into the bottom of the block.
    5. It's a good idea to go ahead and screw the threaded rod into the T-nut as it can be difficult to get the rod to engage the T-nut when the block is mounted.
       1. It is easiest to screw the rod through the bottom of the T-nut then all the way to the opposite end.
       2. Cut the threaded rod so that it is the thickness of your sander plus the thickness of your 1" x 2" top clamp plus 1.25" to 1.5" for the clamp knobs.
    6. Put a flat washer on the threaded rods and tighten a nut onto this washer to lock the threaded rod in place.
14. Replace the blocks on the base using the outlines as guides and clamp them in place.
    1. Put your sander into the blocks and make any adjustments necessary so that it fits snugly between the blocks and is parallel to the long edge of the base.
15. Remove the sander and flip the base over with the blocks clamped in place.
16. Use a fluted countersink bit to drill out the pilot holes so the screws do not protrude past the bottom surface of the base (photo).
    1. if you don't have a countersink bit a drill bit that is just larger than the head of the screws can be used - be careful! If you go this route, try running the drill in reverse to make these countersink indentations
17. Secure the blocks to the base using 1" wood screws making sure the heads do not protrude past the bottom surface of the base.
    1. If any screw protrudes past the bottom of the base, remove the screw and make the countersink hole deeper.
18. Cut a piece of 1" x 2" for the sander clamp.
    1. This piece should be between 2" and 3" longer than the distance between the threaded rods.
19. Drill the sander clamp to accept the threaded rods.
    1. Rods should be between 1" and 1.5" from the ends of the clamp.
20. Replace the sander.
21. Slide the sander clamp onto the threaded rods.
22. Put a flat washer on each rod.
23. Tighten the clamp with 3/8" nuts (photo).
    1. Finger tight should work to secure the sander so that it doesn't move.
    2. We will make some simple knobs to replace these nuts later.

Next we'll look at the sander plate tilt adjustment mechanism.

To make the tilt adjustment mechanism, I used a 3/8" T-nut, a 3.5" hex head bolt, and a 3/8" nut and washer.

• I attached the T-nut to the bottom of a 1"x 2" under the sanding belt housing of my sander and affixed the block to the base from the bottom using 1" wood screws - countersunk of course.
• The sanding belt housing of my sander was 2" from the base so I cut the screw down to 1 7/8".
• My sander had a slight forward tilt so I left the adjustment bolt a little high (photo).
• When I checked the plate there was a slight gap at the top which meant the adjustment bolt was a tad too high (photo).
• No problem! Just use a open end wrench to adjust the bolt, in this case to lower the bolt (photo).
• Until the square is flush with the sander plate at the top and bottom (photo).

OK! the sander is securely mounted to the base and adjusted so the sander's plate is perpendicular to the base. Time to build the table.

This is the critical part of the jig. I wanted the table to be both perpendicular with and parallel to the sander plate. The top of the table should be at or just below the bottom of the front belt roller and between 1 and 1.5" from the top of the back belt roller.

1. Start by marking the position of the front and back of the sander plate on the base (photo).
2. Use the long L-square and the marks you just made to draw a line on the base. This line is parallel to the sander plate and will be used as a reference line for positioning the the table (photo).
3. Now draw two lines perpendicular to the belt line one at the front and one at the back of the table.
   1. My table is 16.5" my base is 20" so I split the difference to more or less center the table and made these lines 1.75" from each end of the base (photo).
      1. Because the table has a slight tilt, the footprint on the base will be slightly less than 16.5" and if you want to calculate that difference you may but it's not that significant and can be adjusted for later.
4. .Cut the front and back table braces.
   1. I used the 2D/3D CAD program, SketchUp to mock up the sander and table so I could determine the height of the braces and the angle of the table (photos).
   2. I set my circular saw to cut a 12.5 degree angle and ripped my 1" x 6" to the heights determined by SketchUp. The front brace in SketchUP was 1 25/64" close enough to 1 3/8"; the back brace was 5 19/64" close enough to 5 5/16".
5. Position the braces along the perpendicular lines drawn earlier (photo).
   
   1. Remember, the short brace goes to the front of the table - I have it reversed in the photo.
6. Set the table on top of the braces and check the height of the table at the front and back rollers (photos)
7. Make necessary adjustments to get the top of the table at the front roller at or slightly below the bottom of the roller and between 1 and 1.5" from the top of the back roller.
   1. My table was 1/4" too high at the front so I slid the entire table toward the back of the base until the table top at the front was at the bottom of the front roller (photo).
8. Attach the table to the braces.
   1. Make sure the table is flush with the braces all along the front and back edges.
   2. Drill pilot holes and countersink these screws so they do not protrude above the surface of the table top.
9. Make sure the top of the table is still at the correct height against the sander's rollers.
10. Use a long clamp and your long L-square to attach the table and its braces to the sander plate (photo).
    1. The L-square will make a small gap between the table and the sander (about 1/16") while also keeping the table parallel to the sander..
11. Trace the position of the braces on the base.
12. Remove the table and braces and drill 3 pilot holes in each outline.
    1. Pilot holes should be one inch from each end of the braces and one in the middle of each brace centered in the outline of the brace.
13. Flip the base over (or just stand it up if you don't want to remove the sander again) and use your countersink or large drill bit to countersink all the pilot holes.
14. Re-clamp the table and braces to the sander using the long L-square as a spacer (as in 10 above) and drive 1" screws from the bottom of the base into the braces to secure the table (photo).
    1. Make sure none of the screws protrude beyond the bottom surface of the base.
15. Check that your table is perpendicular to the sander plate (photo).
    1. If the table is not perpendicular make whatever adjustments are necessary using the tilt adjuster.

Now we are ready to take it out for a test drive!!

I had a piece of scrap plywood that was not even close to being square I thought would make a good test subject (photo).

I set up a temporary fence parallel to the sander belt and ran the piece of scrape through (photo). I moved the fence a little closer and ran the piece through a second time.

The finished product after three passes through the fence (two passes in the last position) (photo).

I'm pretty happy with the results. I think I could have gotten it completely square with another couple of fence adjustments but this was good enough as a proof of concept.

I suppose I should say, this is a non-standard use of a drill and you should proceed with this approach at your own risk. OK, with that out of the way....

I wanted to put some simple knobs on the top to make it easier to secure the sander clamp. I cut these out of a piece of scrap ply that was about 3/4" thick using a 2 1/8" hole saw.

1. First cut about half way through the wood with the hole saw (photo).
2. Using your 1" spade bit drill down about 1/8" for the T-nut (photo).
3. Flip the wood over and compete the cut from the other side, this will keep the ply from blowing out.
4. Run a 1/4" bolt two or three inches long through the knob and tighten the knob to the bolt using a washer and nut (photo).
5. Use the 1/4" bolt to attach the knob to the drill.
6. Use a rasp, resting the base of the rasp on a secure surface hold the rasp at an angle over the knob and engage the drill.
   1. IMPORTANT!! - be sure the drill is spinning the knob so that the top half of the knob is spinning AWAY from the top of the rasp. In this set-up this required the drill to run in reverse.
7. Bring the rasp down gently against the knob and move it from side to side against the surface of the knob.
   1. Be sure to go over the edges to round them off.
8. Switch to a file and repeat the above procedure until you've reached the shape you want.
9. Finish it off by holding a piece of 150 grit sandpaper against the knob for a few seconds.
   1. You can continue using finer grit sandpaper if you want a smoother surface.
10. The knob fresh from the phoney lathe (photo).
11. Apply a little wood glue or better yet, epoxy if you have it to the edge where the T-nut will rest (photo).
12. Use a hammer to secure the T-nut in place.

Finished knob (photo)! Make two.

Here are a few pictures of the completed table prior to finishing, I'm thinking of painting all of the surfaces except the top of the table which I'll finish with oil but I might just oil the whole thing.