Making a zero clearance insert?

[Duncan Potter]

I'm trying to make a zero clearance TS insert from some UHMW material.

My 10" blade comes within about 1/8" (or less) of the top surface of the saw table when fully lowered. I'm not able to lower it enough to "plunge" cut up through the new insert blank. Anyone know of any trick methods? I tried ripping a slot in the underside of the blank but if I ripped it deep enough I'd just about cut the thing in two!

I don't have any smaller blades except my Dado, and that seems like it would defeat the purpose.

Thanks.

[Mark Engel]

I taped the new insert to the top of the original insert with carpet tape, then raised the blade until the teeth just started to poke through. Just make sure to align the inserts as accurately as you can.

To insure that the taped insert stayed in place I put a long piece of scrap over the top and clamped it to the front and back of the saw table.

[Paul Zonneveld]

The way I did it was exactly as you indicated. I use one of the outer dado blades (good for regular kerf blades). I will then clamp a scrap peice of plywood over the blade and insert (some clamp to one side both sides etc. The idea is to keep in insert in place while the cut is being made. With the plywood in place start the plunge cut. I then change out the blades make sure the 10" blade is not seriously hung up on anything on the insert and at its lowest height adjustment. I then clamp the same piece of plywood over the top of the insert and table top from front to back. This will prevent the insert from being shot out if the blade grabs a little when you first start up the saw. Fire it up and then slowwwwwwly raise the blade up through the insert and plywood. I usually go until the bade is about 80% raised and stop. I have a few inserts that go to 100% but I dont extend the blade to full height so its not really necessary to raise it all the way.

[Bas Pluim]

Do you have a circular saw? That blade would work. I've used Mark's method as well, works great. Proper alignment is important, but your ZCI will still be quite "Zero" even if it's off by 1/32".

[Roger Lance]

Duncan...sounds like you might have a Delta Uni...the blade does not go lower than about 1/8" below surface...anyway, use your outside blade of your dado set...of course, you must hold the ZCI down and take all precautions when slowly raising your blade through the ZCI...once cut, replace your 10" blade and then raise it using same precautions and you should be good.

[Duncan Potter]

Thanks to all! I do have a Delta.

I used Marks method because he posted first and it saved me from having to switch blades. Seems to have worked fine.

Time will tell as I use the new insert.

[Greg Hines, MD]

Another approach would be to rout a dado on the underside of the insert, about halfway down, in the middle of it, then you can put the insert in place normally and your blade will have clearance. The dado does not have to be very long to accommodate the blade on most saws.

Doc