Video of jig in use
Step 1: Corner Rounding Jig for a Disk Sander
I made this jig so I could round perfect corners on small pieces of wood with a disc sander. It's made it out of scrap wood, an old beat up plastic speed square, a scrap piece of 16GA steel plate and a drawer slide.
I wanted it to be simple to set up, quick to use and be able to adjust for the radius of corner to be rounded off.
Step 2: Base
I built this jig in two sections.
The base (¾" plywood) with the slider dadoed into it and the rectangular piece of 16GA steel plate to be attached to the slider.
The top (3/8" plywood) with the plastic speed square as a sliding fence.
I cut the base to the same size as the sanders work table, cut a strip of wood for the miter slot on the sanders work table and attacked it to the plywood base square to the disc. With the plywood base on the work table I made two marks on the base in relation to the centre and the left side of the sanding disc. Then I drew a line between the two marks.
I cut a shallow dado the width & depth of the slider centred on this line.
Step 3: Slider
At this point I'm attaching a corner of the steel plate to the end of the slider with a flat head Machine bolt & nut and a brass grommet. I temporally fit the slider in the dado and rounded corner off the steel plate.
I made a thumb screw out of a wing nut, machine bolt & nut to use as a lock on the slider.
Step 4: Making the Top
The top is 3/8in plywood 7"x 7½" with a 1/4in slot routed out for a carriage bolt for the fence.
I notched the top left hand corner with a ½" forstner bit, to access the machine bolt when the top is attached to the metal plate.
Step 5: Fence
I used a cheap plastic speed square for the fence. Used a transfer punch to mark a hole for the carriage bolt. Attached a scrap of 3/4in melamine to the square for a thicker face to the fence. I also added a scrape piece of angle aluminum to the end of the square as a stop block to keep the top from swinging into the sanding disk.
Step 6: Putting It All Togeather
I removed the plate, from the slider and applied double sided tape to attach the plate to the 3/8in plywood top.
Added sand paper to the top and the face of the fence as to grip work pieces.
Reattached the top to the slider and the fence to the top.
Step 7: How to Use
With top swung away (as in the 1st and 2nd pic) you adjust the sider to the radius of the corner you want to make and lock the slider.
Swing the top so the fence is parallel to the sanding disc and slide fence against the work piece and sanding disc(pic 3).
With the fence set, swing the top back so the fence is 90º to the sanding disc (pic 5) and slide the work piece against sanding disc, turn on sander. While holding the wood tightly against the fence rotate the top 90º to sand corner.