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Thread: Zero Clearance Insert (ZCI) Question

  1. #1
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    Zero Clearance Insert (ZCI) Question

    I have a somewhat oddball table saw - Craftsman 21830 Jobsite Model - with a 3/32" steel insert plate. There are no aftermarket inserts available for this saw - believe me, I've checked! I have made inserts out of Baltic Birch, 1/2" MDF (lots of rabbeting edges and the support rod that runs the length of the insert opening and is really the determining factor for the thickness of the insert), and 1/4" hardboard. The plywood was pretty good but chipped badly when the saw blade came up through because some dummy had the grain running across rather than lengthwise. The MDF ones are probably the best inserts but require a lot of work to make them fit. The hardboard was easy but flexed and sagged in the middle where there is no support.

    So, I've been looking and found a source for 3/32" & 1/8" phenolic. Never having played with this stuff, I wonder if phenolic this thin will be strong enough to not sag or flex. I know that phenolic is an extremely tough material but is that compression strength, breaking strength,?????? If anyone has any experience with this stuff, perhaps you could provide some advice. Also what would be the best/strongest grade (CE (canvas), LE (linen), XX (paper), or perhaps some of the glass grades - I know I don't want to use the carbon grade!!!).

    Thanks for any advice.

    Jim

  2. #2
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    I don't hold out much hope for the phenolic at 3/32". My old C-man had thin inserts. I used 1/4" material, rabbeted as you describe and then glued hardwood ribs front-to-back on either side of the blade (underneath). I also glued a hardwood block behind the blade (underneath) to drill into to accept my MJ Splitter. These were indeed fussy to make so I would set aside some time and make a half a dozen at a shot.
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  3. #3
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    Can you modify the original steel insert so as to screw in a piece of plywood or hardboard to make it a ZCI? I would think the problem is to get anything else that thin to be sufficiently stiff. But a scrap of hardwood with a 3/32" rabbet around its edge should be pretty easy to make and attach.

  4. #4
    Can you try a piece of sheet aluminum or brass? These might be rigid enough, yet soft enough for the saw blade to cut through easily when you raise the blade through the insert.

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  5. #5
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    Quote Originally Posted by jim crockett View Post
    I have a somewhat oddball table saw - Craftsman 21830 Jobsite Model - with a 3/32" steel insert plate. There are no aftermarket inserts available for this saw - believe me, I've checked! I have made inserts out of Baltic Birch, 1/2" MDF (lots of rabbeting edges and the support rod that runs the length of the insert opening and is really the determining factor for the thickness of the insert), and 1/4" hardboard. snip

    Jim

    What if you cut a dado in the bottom of a thicker ZCI where the rod is? It would have a weaker point there, but the majority of the ZCI would be thicker and therefore more stable.
    I just recently finished a ZCI for my Ridgid saw that is 3/32" lip at the edges that came with a steel plate that thickness. I used a piece of Corian that is 1/2" thick, and routed out a place for a replaceable wooden insert for the ZCI section. I need to get something better than MDF to use for that, but the main piece looks like it will work well. Jim.
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  6. #6
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    Quote Originally Posted by Jim O'Dell View Post
    What if you cut a dado in the bottom of a thicker ZCI where the rod is? It would have a weaker point there, but the majority of the ZCI would be thicker and therefore more stable.
    I just recently finished a ZCI for my Ridgid saw that is 3/32" lip at the edges that came with a steel plate that thickness. I used a piece of Corian that is 1/2" thick, and routed out a place for a replaceable wooden insert for the ZCI section. I need to get something better than MDF to use for that, but the main piece looks like it will work well. Jim.
    Jim, that is what I have been doing - with 1/2" plywood or MDF - rabbeting around the edges and cutting a deep dado where the rod is located. It works but I'm just looking for something better and somewhat easier to make. Thought the phenolic might be strong enough but have never handled any of that thickness, so I posed the question to the forum. The consensus seems to be that it will not work, so guess I'm stuck with the way I have been doing it.

    Jim

  7. #7
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    Or as Alan suggested, can you enlarge the factory one, even wide enough for a dado head, and mill a piece of wood to fit in from underneath with a lip on the wood to overhang the metal insert? You could drill a series of holes, and bevel countersink the heads to screw in from the top, or bottom but safer from the top, to hold the wood in place. Would this be clear of the support rod? Or is it too close to the blade? Just a thought. Jim.
    Coolmeadow Setters...
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    When Irish Eyes are smiling, they're usually up to something!!
    At a minimum, I'm Pentatoxic...but most likely, I'm a Pentaholic. There seems to be no known cure. Pentatonix, winners of The Sing Off, season 3


  8. #8
    Jim, I had an old Craftsman and it has the same type plate. I used 1/2 phenolic and milled it down to the needed 3/32 with a rabbet bit on the router table. I used it for over a year before I sold the saw.

    I really like using phenolic, it last for ever and is nice and smooth. Some people say you need to change ZCI more often then we do but I can see needing to change it if it opens up but with the phenolic they never seem to. the one on the old Craftsman was still singing when I sold the saw.

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