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Thread: ZCI for Dado: How to keep the ZCI secure to table?

  1. #1

    ZCI for Dado: How to keep the ZCI secure to table?

    I'm doing the ubiquitous ww project: ZCI's for my dado stack. Made out of MDF, pretty proud that I got it to fit exactly in the throat and level with table. Nothing a belt sander and a defective drum sander couldn't fix....

    Since I expected this to happen, threw the switch real quick and of course the dado lifted the insert. Had I not done this test, and been standing behind it and flipped on full power, I'd have a MDF ZCI embedded in my face. Delta 36-725, the stock insert has some sort of clippy thingy in the back to prevent this very thing. Even considering how a ZCI is supposed to work, my healthy respect of the default safety features on the saw result in me not using a ZCI unless I have some way of securing it. Had a extremely violent kickback once many years ago on another saw. That was, and will be, the last safety incident I have with a TS.

    Looking for a low precision, doesn't matter what it looks like as long as it's cheap and easy to cobble together. I'm not that canadian guy that makes router lifts out of wood. I know there are folks out there that can carve/turn/route some complicated retainer thingamajiggers, I am not among that group of craftsmen.

    This seems like a pretty common problem, surely some WW has cornered this market and is selling 5$ clip doo-hickeys for ZCI's? What's his phone#?

  2. #2
    Join Date
    Mar 2008
    Gilford NH
    My Delta saw has a bump on the end to keep it from lifting, I use a piece of #12 wire drilled in the back end away from the the fence rail.

  3. #3
    Join Date
    Apr 2008
    River Falls WI
    On my previous saw a 113 C-Man, I made them with a small Pin in the front of the insert. I have also seen somewhere where some one had like a concentric washer that could be turned under the edge of the insert hole. I use the Infinity Aluminum Insert now with my Sawstop PCS. The only thing is it does not have the lock down lever. Dan

  4. #4
    Join Date
    Mar 2006
    A snipped off nail, a roll pin, I even shaped a beaver tail on some of mine to accomplish this.

    "The Danish government believes that if we train 5,000 designers, and produce
    one Hans Wegner, the money is very well spent." - Ole Gjerlov-Knudsen

  5. #5
    Join Date
    Oct 2008
    Columbus, OH
    Are you trying to cut the slot in the insert, or have you already done that?

    "Any intelligent fool can make things bigger or more takes a touch of genius and a lot of courage to move in the opposite direction." - E.F. Schumacher

  6. #6
    Strap a 2 X 4 across ZCI before raising dado blade. Clamp 2 X 4 in place, front and rear. K.I.S.S. principle.

  7. #7
    What Bruce said. It if still moves after the opening is cut, try the other things. DO NOT hold the backer board by hand. Messed that part up earlier this year and have the scar to prove it.

  8. #8
    I like the beaver tail idea. I just made one from some scrap steel stock, seems to work just like the factory insert, thanks!

  9. #9
    Join Date
    Dec 2014
    Hmm, now you all have me worried. I just made mine out of some very thin plywood I had sitting around. I believe it was 3/16". I don't have anything to clip it into place. I just made it fit snug, put my fence on one side, a sacrificial piece of ply on the other (clamped), then raised the blade full height. I raised the blade up and down a few times, just to make sure everything was cut well. I used it for 3 hours the other day with no ill effect?

  10. #10
    TO clarify, the question is not related to the initial blade raise/cut, it's related to: Ok now I've been using it for 2 weeks, a thunderstorm rolls in, humidity causes the wood to expand, I throw the switch for the saw on, and I get a face full of ZCI. Which is exactly what happened in my "experiment"...sort of. Didn't move far, but made me realize an unsecure ZCI could get caught by the blade and launch. I made a metal 'beaver tail' which seems to work perfectly.

  11. #11
    Join Date
    Apr 2010
    Nashville, TN
    I make mine 1/2 thick and put a small finish nail in the back of them that slides under the cast iron top when its installed.

    There are also set screws that are installed to raise it up flush with the top surface. The set screws contact 4 tabs in the throat opening.

  12. #12
    Join Date
    Sep 2016
    Modesto, CA, USA
    The one on my saw has no holding provision other then gravity. It is cast iron and weigh. 6.8 pounds. I will have to think how to secure it better. I have been thinking about how to make a ZCI for that saw. Problem is the insert only goes the left of blade. The right is just the tabletop with 1/8" gap and no width to put i nmush of anything. maybe glue on a piece of wood.
    Bil lD.
    Last edited by Bill Dufour; 10-26-2020 at 12:48 AM.

  13. #13
    I usually use 1/2" Baltic birch for making ZCIs. Four set screws with a little glue holds them. For retention I use a small round screw, again with a little white glue to prevent loosening through vibration.


  14. #14
    Join Date
    Jan 2010
    Tampa Bay, FL
    Quote Originally Posted by Bruce Wrenn View Post
    Strap a 2 X 4 across ZCI before raising dado blade. Clamp 2 X 4 in place, front and rear. K.I.S.S. principle.
    That's what I do. With my sawstop, once the insert was made, it doesn't lift up.

    Of course, a few years ago, I managed to fire the cartridge on my dado blade making an insert. That was a $265 mistake.
    - I have enough frequent flyer miles to orbit the sun. Sigh...
    - After I ask a stranger if I can pet their dog and they say yes, I like to respond, "I'll keep that in mind" and walk off.
    - When you earnestly believe you can compensate for lack of skill by doubling your effort, there's no end to what you can't do

  15. #15
    Join Date
    Dec 2016
    Houston, TX
    For my PM, I use small cup magnets attached with small screws. These also work as the height adjustment for the ZIC to make the ZIC flush with the table.

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