Light Thicknessing With a Radial Arm Saw




About: I miss the days when magazines like Popular Mechanics had all sorts of DIY projects for making and repairing just about everything. I am enjoying posting things I have learned and done since I got my first ...

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.

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. 



    • Tape Contest

      Tape Contest
    • Trash to Treasure

      Trash to Treasure
    • Gardening Contest

      Gardening Contest

    11 Discussions

     A very good ible Phil, even though personally I would be scared of the exposed blade (I know you take every precaution) I guess is just the picture. I would have gone with the more traditional method for this - vertical cut on the table saw with a spline miter jig to cut the joints. The sanding method is perfect.
    Thanks for sharing  

    2 replies

    A table saw with the right jig would have been ideal for making the kerfs, unfortunately, I do not have a table saw.  One thing in my favor was that the movement of the jig and the work piece were from right to left, not toward the blade.  Another was that I purposely held the work piece with only a little downward pressure from my fingertips.  If anything had pulled the work piece from my hand, my hand would not have been pulled toward the saw.  I probably could have used two pusher sticks: one to hold the corner of the work piece in the jig and a second to push the jig across the blade.  Compare step 4 in this Instructable.   

    Thank you for your comment.  I enjoy your Instructables.

     Oh! I see now, I thought you had a table saw.
    Yes I understand completely how and why you do it now.
    I would then recommend an instructable to you,  by Phil B "A precise table saw from an electric hand saw" he might teach you a thing or two. So no excuses not to have one now hehehe


    9 years ago on Introduction

    Shortly after you published it, I received a lot of boxes that suffered from age and transportation, so I remembered your ible. I don't have such a disc saw, but you inspired me for a similar solution, using a cordless drill, and diagonal tenons.

    Thank you my friend for this great ible. For this you'll get a patch.

    1 reply
    Phil Blaxap

    Reply 9 years ago on Introduction

    The great thing about Instructables is that we sometimes adapt someone's idea to use it in a new way he never considered.  I am glad I could be of help.  Thanks.


    9 years ago on Introduction

    The position of the saw in picture is very dangerous. Half of the blade is exposed.  If the blade grabs the wood you are cutting, your hand could hit the blade. I know you can do this 100 times without a problem but watch on the 101th.

    3 replies
    Phil Bfoxwoodfarm

    Reply 9 years ago on Introduction

    There are some things I cannot show in the photo because my other hand is holding the camera rather than assisting in making this cut.  Please notice how my left hand is positioned.  If it were possible for the saw to pull the wood into the blade, my hand is positioned so that the wood can be pulled away from my hand without pulling my hand toward the blade.  I appreciate your concern.  I considered all of the things you mention before I commenced and made my kerfs very safely, although also very, very cautiously.  If I let the 101st time completely dominate my thoughts, I would never turn the saw "on."

    Phil Blaxap

    Reply 9 years ago on Introduction

    I remember viewing your Instructable quite some weeks back.  Although I have not triedd it, I fear my teeth would not hold the camera steady enough.  I would probably be more inclined to set the camera on a tripod and use the self-timer.  Thank you.

    Phil Bmerijnvw

    Reply 9 years ago on Introduction

    Thank you.  And, it is unbelievably useful.  In addition, passing work between a sanding drum and a flat guide tends to straighten the work.  See my related Instructable on jointing boards with a sanding drum and a fence on a radial arm saw, or on any other sanding drum setup.  That is really useful!