* An original DeWalt DWE7491RS table saw insert to use for a pattern.
* Board, the same thickness as the zero clearance insert above.
* Small piece of scrapwood to serve as a cam. This will be the cam that holds the plate down. The exact size doesn't matter, but maybe 3/4 x 3/4 x 4 inches long, something like that. It must be wider than the T-nut below, and also thicker than the length of the T-nut. The T-nut should not protrude from the scrapwood cam.
* Small bolt. This will be used to rotate the cam in place.
* 1/4 #20 T-nut. Like this: https://www.rockler.com/tee-nuts-select-size
* Flat head screw, 1/4 (#20)
* Set screws. I use M6x8 set screws, but any set screws will work.
* Blue or masking tape
* Glue - Nearly any kind will do. Wood glue, CA (super) glue, epoxy, or even white glue. I do NOT recommend polyurethane (Gorilla) for this use.
* Sharpie marker pen
* Sharp point (nail) for marking.
* Jigsaw, bandsaw, scrollsaw, table saw or any other cutting to make the rough shape.
* Router pattern bit
* Thin double-stick tape for router pattern matching
* Small hand saw or a file or a Dremel tool or other small cutter/sander/grinder to shape tabs.
* Handheld drill or drill press.
* Socket wrench or driver, plus socket to turn bolt.
* Hammer to tap in the T-nut.
... and several drill bits, see below. Consider buying a brad point bit set or sets, metric and/or imperial. A forstener bit set is also nice to have. IMPORTANT NOTE: The drill numbers below are for identification only, not size:
* Drill 1 to match the finger hole.
* Drill 2 for the set screws. I found that a 5 mm drill bit works for M6x8 set screws. Test the drill bit on scrap to make sure that the set screws will thread snugly in the holes.
* Drill 3 large enough to leave clearance around the bolt head to turn it with fingers or a socket. A flat bit would be best, such as a forstener, brad point, or spade bit, but you can use a regular twist drill if you must.
* Drill 4 one size larger than bolt shank threads. The bolt should slip through this hole.
* Drill 5 to match bolt shank threads, so the threads engage lightly. Test the drill bit on scrap to make sure that the bolt threads easily. You will not need a "tap" for this.
* Drill 6 for the 1/4 (#20) screw, one size larger than the screw threads, so the screw threads do not engage.
* Drill 7 for the T-nut. It could be the same as the Drill 6 above.
* Drill 8 - to use as a countersink for the 1/4 (#20) screw. Make sure it is wider than the screw head. This could be a simple twist drill bit.
* Read all instructions first, to make sure you understand what you are going to do.
* I suggested a 1/4 (#20) screw size because it is common and will work fine. Use what you want that fits.
* I suggested M6x8 set screws, but any set screws will work.
0. Lower the table saw blade fully, and unplug the saw.
1. Cut the rough shape out with a jigsaw, bandsaw, or whatever.
2. Flip the original insert over and tape it to your board.
3. Mark the finger hole for later drilling.
4. Use the router and pattern bit to copy the shape of the original insert. Be sure to include the tabs at the end!
5. (Drill 1) Remove the original insert and drill the finger hole in your insert where you marked it.
6. Use a small handsaw, a file, a Dremel tool, a grinder, or whatever to shape the tabs for a snug fit. Keep testing the board until it is perfect. (You may have to adjust it later after you add the set screws.)
7. Tape the paper to the original insert and mark the locations of the set screws and the cam lock.
8. Move the paper to your insert. Use the nail or pencil to transfer the locations of the set screw holes and the lock cam to your insert.
9. (Drill 2) Drill the set screw holes now. You can insert the set screws if you wish, but keep them inside the insert plate. Don't let them protrude yet.
10. (Drill 3) Use the flat bottom bit to make a stopped
(partial) hole at the back of the cam area. The hole should be slightly deeper than the thickness of the bolt head, deep enough to clear the bolt head plus a small additional gap, approximately 1/16 inch. The remaining wood can be pretty thin. Be sure that this hole is far enough in front of the blade kerf that it will not interfere with the blade or saw mechanism, on the blade side where the back of the locking cam would normally be. Flip the bolt upside-down in the hole to test the head, ensuring that it is below the surface of the insert with extra clearance.
11. (Drill 4) Drill a hole all the way through the center of the flat hole you just made. Test the bolt to make sure it slips easily through the new hole, with the head resting on the bottom below the surface of the plate with room to spare.
12. (Drill 5, kinda) Hold Drill 5 next to the bolt protruding from the bottom of the plate. Wrap tape around the drill bit to mark the depth to match the bolt protrusion.
13. (Drill 5) Use the "bolt size" drill bit to drill a stopped hole near one end of the scrapwood piece. Stop at the tape.
14. Thread the bolt through the insert, and gently tighten it in the hole in the scrapwood (cam). Check the following:
15. CHECK: Verify that the bolt doesn't bottom out in the hole with the scrapwood too loose against the bottom of the insert plate. If so, (DRILL 5) drill the hole slightly deeper and check again.
16. CHECK: Verify that the scrapwood "cam" rotates easily when you turn the bolt head. If not, loosen the bolt very slightly until it does.
17. CHECK: Verify that the bolt head does not protrude above the top of the insert. If it does, go back to step 10 and drill the flat bottom hole slightly deeper (Drill 3).
18. Put a very light coat of glue down in the hole. You want to avoid "squeeze out". Thread the bolt through the insert and into the hole. Tighten the bolt in the hole. Do the following checks again:
19. CHECK: Verify that the scrapwood "cam" rotates easily.
20. CHECK: Verify that the bolt head will never protrude above the top of the insert. (IMPORTANT: If this check fails. STOP NOW and quickly remove the bolt before the glue cures. Go back to step 10 and drill the flat bottom hole slightly deeper (Drill 3). You may need a new bolt and you may have to e-make the scrapwood cam, too.)
21. Allow time for the glue to cure.
22. Turn the board over and rotate the cam so that it extends beyond the front of the insert. Tape the cam down to the insert so it doesn't move.
23. (Drill 7, kinda) Hold Drill 7 next to the scrapwood cam. Wrap tape around the drill bit to mark the depth to match the scrapwood cam.
24. (Drill 7) Drill a hole through the "bottom" of the scrapwood cam for the T-nut. Stop drilling when you reach the bottom of the insert, at the tape marker. If you drill slightly into the bottom of the insert, don't worry about it. Be sure the hole goes through the scrapwood cam.
25. Swing the scrapwood cam out of the way and look for the drill hole mark on the bottom of the insert. If there is no drill hole mark (really!), make sure the scrapwood cam is pointed forward and use the hammer and nail through the hole to make the mark.
26. Use the hammer to tap the T-nut in the bottom of the scrapwood cam.
27. (Drill 6) Swing the scrapwood cam out of the way and drill a hole through the bottom of the insert for the 1/4(#20) screw.
28. (Drill 8) Gently drill a countersink in the top of the insert for the 1/4(#20) flathead screw. The head must rest below the surface, but it must also rise up high enough to pinch and remove when you unscrew it. Drill a little bit at a time and test it. Swing the scrapwood cam out of the way and poke the bottom of screw with your finger to test it.
29. Remove the 1/4(#20) screw.
30. Rotate the scrapwood cam so that it is underneath the screw hole. Insert the 1/4(#20) screw. Wiggle the scrapwood cam to line up the T-nut and tighten the screw. Perform the following checks:
31. CHECK: Verify that the screw head is below the surface of the insert.
32. CHECK: Verify that the bolt head is below the surface of the insert.
33. Use the Sharpie marker to draw an arrow on the top of the bolt, pointing to the front of the insert plate. This will help you align the cam when you can't see it.
34. Remove the 1/4(#20) screw.
35. Swing the cam out of the way and drop the insert into the saw. Adjust the set screws until the edges of the insert match the top of the table saw.
36. Verify that the scrapwood cam will swing under the front of the table. Use your fingers or a socket to rotate the bolt until the arrow points to the front of the insert. If necessary, trim or sand the scrapwood cam to fit.
37. Insert the 1/4(#20) screw and tighten it to lock down the table saw insert.
39. VERY IMOPORTANT CHECK: Use the finger hole to test that the insert is truly snug. It should not move at all. If it moves, don't use it; fix it until it doesn't. You may want to add a shim to the top of the scrapwood cam or check the set screws again.
38. Don proper safety gear. Make sure the blade is fully lowered. Stand off to one side and turn on the table saw. Wait for the blade to come up to full speed. Slowly and carefully raise the blade to create the zero clearance slot.