....have any of you made a insert for your saws, for dado blades?
I have about six homemade inserts (1 for TK, 1 for full kerf, three for different sized dadoes and one for a moulding head. ) I also have 10 more squared blanks awaiting bandsaw time to round out the ends and then drill the screw hole.
I start with "1/2" ply (15/32) and cut it to 3 23/32w x 14 3/8 long. I then cut a 1/2"w x 1/4" deep rabbet across one end to allow for a 3/4" wide tongue in the back. (Actual dimensions of the insert without the tongue are 3 23/32 x 13 7/8". I then trace the curves from the original and bandsaw them. I finish up with 4-in-hand rasp to get a good fit. I use the original or one of my others to locate the hole for the #10 screw and countersink it.
If you have a template bit for your router, you can use the original as template. Just don't cut into the tongue of the original if you use a top bearing bit.
I adjust the height with about 3 layers of duct tape on the ends, which brings it up flush with the table top.
For ZCIs for a full 10" blade, you will either need to cut a 1/4" deep slot in the bottom over the blade (the 10" blade only drops 1/4" below the table top and the insert is 1/2" thick) or start the cut with a smaller (i.e. circular saw) blade. This is not a problem with 6 or 8" dado sets. I install the insert and put the fence over the right third when running the blade up through it the first time.
My full kerf ZCI I made from a piece of HDPE (Plastic) and it works really well, and some have used corian scraps. The rest are Lowe's Arauco ply which works fine. You can cut the curves with a jigsaw or hand coping saw if you don't have access to a bandsaw (I didn't have a bandsaw when I made my first ones so used a jigsaw).
I would suggest making several at a time. The way lumber dimensions are changing, (I have seen "3/4" ply ranging from 19/32 to full 3/4) and the brittleness of some causing tearout, its nice to have a spare to quickly make one for the exact width of dado.
Go
PS: The above dimensions are for the Ridgid TS3650.