How do I cut the slot in a zero clearance insert?

Years ago I made a zero clearance insert and it's been useful ever since. Today I find I need one for the blade at a slight angle and the other one won't work. I was going to use the metal one that came with the saw, but the cast light metal disintegrated when I put it in! I cut out a new blank, shimmed it up and sanded it until it fit perfectly. But I forget how I cut the slot in the other one. I can't crank my 10" blade low enough to clear the 1/2" plywood of the insert. I'm pretty sure I didn't own a smaller blade the last time I did this, so how did I do it? I own a smaller blade now (for my skilsaw), but I'll have to check if the arbor will fit.
What obvious thing am I missing?
Thanks.
- Owen -
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The only place you ned 0 tolerance is the top of the insert. So, create a channel (with a router) on what will be the bottom of the insert, deep enough to clear the saw blade when fully lowered and wide enough for wiggle room to fit the blade width. Screw the insert in, start the saw and very slowly raise it and cut through the insert.
FoggyTown
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The smaller diameter blade is the answer. If you don't have a regular blade consider using one blade from a stacked dado blade package. A 6 or 7 1/4 inch blade should give you the clearance you need to fit your zero clearance insert. Then you can set the blade angle and just raise it up through the insert to make that angled zero clearance cut. Your 10 inch blade may rub a bit the first time that you use it, so be careful on the first start to be sure it doesn't jam.
Charley

forget
enough
smaller
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Okay, I used my 7-1/4" blade. The only problem is that it's a thin kerf blade, and for my immediate needs that turned out not to be any problem at all. I just made all my cuts using that exact blade.
Now that I've made a slot, I know where to chase it with my router to widen the underside a bit. This particular insert is not destined to be a zero clearance insert anyway, now that I think about it. It's just a replacement for the metal one that shattered, which had a gap to accommodate small angles.
I think when I made my first one I must have clamped it to the surface of the table saw, over the original insert. It was okay to do that because it was just a perpendicular cut.
Thanks for the suggestions.
- Owen -

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"Owen Lawrence" wrote

replacement
For angled cuts that's the way it should to be ... much safer. Too easy to forget and bend a blade, or have the blade push upon the insert on start up and throw is back at you should you raise the blade a bit too high and don't have a hold down pin installed.
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Last update: 11/4/07
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I do have a hold down hook at the back.
- Owen -
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Damn.. I just recovered from a senior moment, Swing.. thanks..
I made 2 inserts, a zero clearance and a dodo.. I use the dado insert of angles... DUHHH
mac
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Owen... I did the same thing once and didn't bother with the router, though if you're skilled with one it might be easier for you.. I just used the wife's dremel and a round burr to widen the bottom 2/3 of the slot cut by the circular saw blade, then put it back on the TS and cut the rest of the way through..

mac
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On Sat, 10 Nov 2007 08:40:37 -0500, "Owen Lawrence"

There are a lot of ways you can do it, probably the easiest is placing the new insert in position over the old one, holding it down with clamps and a caul, then raising the bit into it so that you cut out enough material so it can be installed and cut the rest of the way.
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Brian Henderson wrote:

This won't work for an angle cut. When the partially sawn insert is dropped down into the table the location will be different. It would work for a vertical cut.
--
Gerald Ross
Cochran, GA
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wrote:

No, it won't work for an angled cut but then again, raising a blade into an insert at an angle isn't the best idea to begin with. If I had to make an insert for angled cuts, I'd start out with the normal vertical cut, then pare out the excess with a chisel.
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I just went through this, Owen... Since I didn't own a 9" blade, I used my old crapsman wobble dado blade... I set it at about 5/16" and raised the blade until I was about 1/2 way through, then swapped blades to my normal 10" one that I use most often and cut the rest of the way through... Since you're talking an angle, a wider beginning cut might be better.. The 2 inserts that I bought the first time had starter cuts on the bottoms..
mac
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You put the fence on the edge of the current plate. Lower the new insert onto the running blade...with the old one still in place. Just a little at the time.
That's how I did this one:
http://i123.photobucket.com/albums/o290/Robatoy/Zeroclearance.jpg
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That looks good. Now try to make an angled one, and when you get out of the hospital let me know how it turned out.
- Owen -
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You just have to think this through. If you angle your blade, using your standard insert, you then cut a section of 1/2" MDF and clamp it into place. (Don't finish the cut) THAT becomes your zero clearance for the few cuts you need to make. (If you don't 'get it', don't 'do' it.
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Sorry, I don't get it. Do you mean clamp it into place recessed into the table in its final destination, or on top of another insert? If I've got a 10" blade then I can't clamp it into the recess because I can't lower the blade far enough. If I clamp it on top of another insert then the slot will end up in the wrong position because of the angled blade. Remember, my "standard insert" went kablooey so I have one less option, too.
- Owen -
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This Quick and dirty method comes to mind:
Set the blade at 90, in the lowest position. Set the back if the insert into the recess and gently pivot the front down onto the spinning blade. It's a little dicey, but not that tough; just stay out of the throw zone. Secure your insert in place, then crank your bevel over with the saw running, then raise you blade.
Although, if I where doing a batch of inserts, I would probably take the time to set up the router to plunge a stopped dado in the bottom if the blanks.
While you're at it, make a half dozen blanks. I ZCI's for: 90, bevels at 45 and 7, 1/2" dado 3.4" dado, 1/4"double-blade tennon cutting and 3/8" double blade tennon cutting.
Bad things can happen when an offcut is too narrow to be supported by an insert, The offcut can jam by the blade and/or get kicked back. IME it takes about twice as long to make 6 ZCI blanks as it does one, so it makes sense to have them to the vast majority of your cutting scenarios.
Steve
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