Introduction: Light Thicknessing With a Radial Arm Saw
Frequently I need to make something small an exact thickness. Here the piece of oak needs to be reduced in thickness to fit into the saw kerfs on the corners of this child's toy. It is easy with a sanding drum on a radial arm saw and an auxiliary table.
Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.
Step 1: First, Cut the Kerfs
The toy is a wooden frame with a swinging yellow door in it. A child threw a tantrum and then threw this. The joints were end grain glued, and several broke. Just to get started, I glued the pieces back together just as they had been. I decided to make kerfs and add glued splines for strength. The jig is from a previous Instructable on accurate miters with a radial arm saw. I have set the motor so the shaft is vertical. The jig slides from right to left against the fence. Each corner has two kerfs, so after cutting one set, I turned the toy over and cut the second set. This is about as close to the blade as I care to get my fingers without using pusher sticks.
Step 2: The Setup
I made this auxiliary table for jobs such as this. It is about four inches high and a little more than a foot long. Clamp it to the saw table. Remove the saw blade and guard. Turn the motor to the 'in rip' position and put the sanding drum on the 1/2 x 20 threads on the backside of the motor (opposite the side for the saw blade). Crank the arm down until the sanding drum just touches the top of the piece to be thicknessed.
Step 3: Push the Work Through
Push the piece to be thicknessed against the rotation of the sanding drum. If you were looking at the end of the sanding drum, its rotation would be counter-clockwise. Push the work from the bottom right of the photo toward its upper left. Keep the work moving so no cupping forms in the surface of the work. Make several passes until the drum hardly cuts at all. The amount of cut should be very light to avoid burning. I like to turn the work over periodically and sand a bit on both sides. This takes irregularities out of both surfaces.
The crank on this Sears Craftsman radial arm saw raises or lowers the arm 1/8 of an inch per full turn of the crank (not visible, but located under the table). I made each new cut only about a 15 degree change in the rotation of the crank.
With a little practice you can become smooth at the transition from pushing the work from one side to pulling it from the other when the end nears the sanding drum and your fingers cannot follow the work under the sanding drum.
Step 4: The Fit
Here you see the same piece of wood shown in the Introduction photo, but it has now been reduced in thickness so it slides easily into the kerfs. The fit should not be too loose, but should also allow a little room for glue.
Step 5: Mark and Cut Triangle Splines
I used a speed square to mark the newly thicknessed piece so I could cut it into triangles on my bandsaw.
Step 6: Spread the Glue
I want the triangle pieces to be glued in the kerfs very well. I used a toothpick to spread the glue inside each kerf. Then I smeared some glue on both sides of each triangle, but only as I was ready for each joint.
Step 7: Insert the Triangles in the Kerfs
Here you see the triangluar pieces glued and placed into the kerfs. After the glue is dry, trim the edges of the triangular pieces and sand them smooth.
Step 8: Finished
The edges have been sanded. Apply a little shellac or varnish, and the toy pieces are ready for play. These will never break again.
I have thicknessed all sorts of things this way over the years, and it is always a very handy way to do the job.