My first ZCTP

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  • My first ZCTP

    Hello Gurus,

    Now that my saw is raising and lowering I am excited to build more accessories for my saw.

    Trying to make my first ZCTP and struggling to figure out the correct cutouts. Which holes do you guys use to secure the ZCTP. Do you guys use A & C or B & D in my photos?

    Also I am trying to understand what mpc has tried saying in this post -
    https://www.sawdustzone.org/forum/di...005#post832005

    I tried making one that sits on the lower tabs (like in photo 3) following the above post and ignoring the 0.1" lip. But that doesn't seem right. The drop of 0.1" or so seems big enough for the material being cut to get obstructed on the rear side. Clearly I haven't understood that post correctly.

    May I see some photos of ZCTPs you have built.

    Thanks a bunch in advance.

    NG

  • #2
    I threaded holes A and C in your pictures. My ZCTP fits inside the opening as you show in pics 3 and 4. However, my upper ZCTP surface is even with/flush with the top of the table saw. So only the small rectangular spaces (basically at holes B and D) have "drops" in them. The vast majority of the throat area is flush with the regular tabletop; having those small areas a tad lower hasn't been a problem for me.

    If those drops do concern you though, some options are:
    1: make your ZCTP blanks longer, cutting rabbets on each end to cover holes B and D. I'd still use screws in A and C though as the ZCTP material - assuming you make your ZCTPs out of wood or MDF - would be too thin to have any strength to hold screws.

    2: an easier approach might be to make the core ZCTP piece sit inside the opening (as your 3rd and 4th pics show) and be flush with the B and D surfaces instead of being flush with the main tabletop surface... and then glue on a thin veneer layer over the entire area - B, D, and the central ZCTP blank - to bring the final ZCTP flush with the main tabletop. The veneer would thus creat the rabbet joints. This would also be a lot easier method if you don't have a dado set yet compared to making the rabbets of option 1.

    mpc

    Comment


    • #3
      I use B & D. Even with rabbeted hardwood ZCTPs it works. There doesn't need to be much material thickness for the screws as they simply hold it in place. As mpc says make sure you are flush with the top of the table. Stytooner (LeeWay Workshop, SharkGuard, etc.) made or had them made from HDPE once deciding Lexan was not the best choice. I have a variety of sawblades and consider a ZCTP a wear item. When the slot becomes a bit too wide for best results it becomes a Dado ZCTP.

      Perhaps IMHO the most important tip is to make sure the blade clears the bottom and that you hold a board over the top by mechanical means while cutting the blade slot the first time, slowly lifting the blade.

      just another brick in the wall...

      Comment


      • #4
        Either A-C works or B-D
        I seem to recall the four holes you call A-C Does not come tapped (threaded) from the factory but its easy to run a 8-24 tap through it. I just checked mine and they are tapped I probably did it at some point. They may even come with self-tapping screws.

        Whichever you use should have the plate solidly sitting on the surface with the hole.so things don't flex and distort,
        I don't tighten the screws hard at all, because it distorts the plastic throat plates - the B-D holes are very thin there. There's no real forces on the plate requiring more than just snugging them.

        The screws they give you are 8-24 x 3/4" long which is way more than needed for B-D but probably right for A=C which are set deeper.

        TO me this is the key thing. The plate must be very flush with the surface of the saw,.say between -3 mils and 0 mils. That is from about flush to 3 mils below the table. Flush means you can slide a steel rule across the top of the plate and not catch it when moving from the table to the plate. My plates from Ryobi were never quite that good (I assume manufacturing tolerances) but I simply shimmed my plates up with some metalized address label stock that was about 3 mils thick, using as many as I needed.

        Why so tight? So small pieces won't catch as you are feeding them across the blade. And so that depth of cut settings for the blade hold for big pieces and small. Also I think you need to adjust your SMT so it is level with the main table.

        Anyway, if you are making a throat pate then you need to decide whether its going to register on B-D or A-C or maybe both.
        Youre going to have to cut rabbets on a any plate of adequate thickness. wider Rabbets can be made on a BT3 with multiple parallel passes.

        The BT3 FAQ has some specific advise on cutting a zero clearance slot... if the plate is too thick it may jam against a 10" blade and destroy your expensive and hard to get belts

        My honest evaluation of your picture says you have the top of your plate set way too low. 0.1" is way more than my -0.003" I would allow!

        I will measure my Ryobi accessory plastic ZCTP blank for you.





        Loring in Katy, TX USA
        If your only tool is a hammer, you tend to treat all problems as if they were nails.
        BT3 FAQ - https://www.sawdustzone.org/forum/di...sked-questions

        Comment


        • #5
          I posted pictures and the dimensions here https://www.sawdustzone.org/forum/di...ry-option-zctp

          Click image for larger version  Name:	ZCTP Dimensions.JPG Views:	0 Size:	69.1 KB ID:	843417

          Click image for larger version  Name:	P3190297.JPG Views:	0 Size:	124.9 KB ID:	843415

          Click image for larger version

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          Attached Files
          Last edited by LCHIEN; 03-19-2021, 10:52 PM.
          Loring in Katy, TX USA
          If your only tool is a hammer, you tend to treat all problems as if they were nails.
          BT3 FAQ - https://www.sawdustzone.org/forum/di...sked-questions

          Comment


          • nicer20
            nicer20 commented
            Editing a comment
            This is super helpul and thanks a million for all the help.

            - NG

        • #6
          Thank you mpc , Black walnut & @LCHIEN: All super helpful as usual. Can't thank you all enough for all the insights.

          @LCHIEN: Your honest evaluation is very much on the money. In fact that was my primary concern for the post. When I made mine, the way I have done, I started to see the problem it being too low. I had clearly misunderstood MPC's post. Of course, entirely my problem - not his as he was referring to some other gap. (So please please this is not at all a criticism of anyone or any post).

          mpc: I am now following some of your suggestions - trying to put another layer on top of that plate. But I don't have a planer so I am trying to use some other ideas.

          BTW I have a BT3100 and it seems all the holes are already tapped - don't know if the previous owner did it or factory did it.

          And I am going to follow the BT3 FAQ suggestion to use a 7 1/4" blade to create a relief first before using the 10" blade. Can' take chances with the belts as the saw has started to become more useful after overcoming the raising/lowering mechanism problem.

          Now to the shop to make the ZCTP.

          Thanks a million again,

          NG

          Comment


          • #7
            If you make one too thin you can always add aluminum tape to the bottom to build it up until it is level.
            just another brick in the wall...

            Comment


            • #8
              This project got pushed on a back burner due to many things in personal life and other projects.

              I had initially started with a smaller plate as shared above. I followed many suggestions by mpc, LCHIEN, Black walnut above and beefed up the plate by gluing another layer on top. Then routed out rabbets and holes to get the proper fit and level.

              Finally had the joy of spinning blade emerging out.

              Thanks everyone again for invaluable inputs.

              One thing though - now there is a lot of sawdust that doesn't get sucked by the shop vac connected to the dust port. Guess more shop hacks in order.

              PS - For anyone reading this in future, Given that the material I used is MDF (fragile as compared to Hardwood) I ended up using holes A & C. On my BT3100 all these holes were pre-tapped for #10-24 screws. I used 1" long screws with countersinking.


              - NG
              Attached Files

              Comment


              • #9
                Hey, that looks good!
                Hope you made more than one!
                for various dado blades.

                Also, don't do my trick and try to tilt the blade while using this zero clearance throat plate! Done that too many times. Binds right up and is hard to tilt. Fortunately not made the mistake of starting the saw with the blade jammed which would surely break the belts.

                Has anyone made a zero clearance throat plate and then cut it for 0 degree and some bevel cut like 30 or 45 degrees so that the opening just clears a range of tilt but is minimum opening? How'd that work out?
                I would lower the blade and with it spinning first cut 0 degrees (blade vertical) and then stop, lower the blade, tilt it, start it and raise it.
                I think it would give a smaller opening than the metal one that comes with the saw but allow tilting unlike a ZCTP.
                Last edited by LCHIEN; 10-02-2021, 03:23 AM.
                Loring in Katy, TX USA
                If your only tool is a hammer, you tend to treat all problems as if they were nails.
                BT3 FAQ - https://www.sawdustzone.org/forum/di...sked-questions

                Comment


                • #10
                  Me thinks that if you lower the blade, install the uncut zctp and then tilt the blade… any angle… then raise the blade thinking you will get an angle cut? You will get a slight cut then jam the blade against the uncut area of the zctp. Just like tilting the blade on a compound sliding miter saw and using it in the chop configuration vrs the sliding configuration.

                  Comment


                  • #11
                    Originally posted by capncarl View Post
                    Me thinks that if you lower the blade, install the uncut zctp and then tilt the blade… any angle… then raise the blade thinking you will get an angle cut? You will get a slight cut then jam the blade against the uncut area of the zctp. Just like tilting the blade on a compound sliding miter saw and using it in the chop configuration vs. the sliding configuration.
                    I think If you raise a tilted blade the blade stays in exactly the same plane so if will cut a slanted slot at the tilted angle.

                    The BT3 and most saws raise the tilted blade like A, not like B I think you are describing. B would jam but A would not but simply cut the slot... since the saw raises by moving the motor in the tilted locker bracket.

                    Click image for larger version  Name:	Saw tilt - tilting arbor saw.JPG Views:	0 Size:	46.8 KB ID:	845602

                    However the center of rotation axis of the tilting locker bracket is below the table top slightly. So that the OEM throat plate has a half inch wide slot for the blade... to allow it to tilt.

                    Click image for larger version

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                    I simplified the BT3 mechanism for the above shots. the actual mechanism is more like this

                    Click image for larger version

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                    So be aware the motor, pulleys belt, arbor are all mounted to the saw guide holder and the holder as a unit slides up and down in the locker bracket. The locker bracket is hinged to allow bevels and the hinge is located near the very top of the bracket near the table top and just to the right of the blade.
                    Last edited by LCHIEN; 10-03-2021, 03:52 AM.
                    Loring in Katy, TX USA
                    If your only tool is a hammer, you tend to treat all problems as if they were nails.
                    BT3 FAQ - https://www.sawdustzone.org/forum/di...sked-questions

                    Comment


                    • #12
                      Originally posted by LCHIEN View Post
                      Hey, that looks good!
                      Hope you made more than one!
                      for various dado blades.

                      Also, don't do my trick and try to tilt the blade while using this zero clearance throat plate! Done that too many times. Binds right up and is hard to tilt. Fortunately not made the mistake of starting the saw with the blade jammed which would surely break the belts.

                      Has anyone made a zero clearance throat plate and then cut it for 0 degree and some bevel cut like 30 or 45 degrees so that the opening just clears a range of tilt but is minimum opening? How'd that work out?
                      I would lower the blade and with it spinning first cut 0 degrees (blade vertical) and then stop, lower the blade, tilt it, start it and raise it.
                      I think it would give a smaller opening than the metal one that comes with the saw but allow tilting unlike a ZCTP.
                      Thanks and No so far only made one.

                      I don't have any dado blades yet. That's next on my purchase list.

                      And I should make more for other blades like the Diablo 10=60 and DeWAlt 10-24 rip blade I already have.

                      - NG

                      Comment


                      • #13
                        Frankly I don't see a need for making a ZCTP for every blade. Especially if they are the same kerf, whats the point?

                        I don't even really see much point for making ZCTP for blades of different kerf... like .125" and .093". Because the opening only about .014" or so on each side. does that improve anything? OK, maybe tearout support.
                        To me the biggest value of a ZCTP is to keep offcuts from falling into the opening and jamming my DC and jamming the blade.
                        I'm not seriously worried about offcuts in the .015" range.
                        OTOH, supporting the blade all the way to the very edge can reduce tearout on the bottom side of the cut?

                        Tearout is not an issue for ripping cut.

                        How does anyone else feel about that?
                        Last edited by LCHIEN; 10-03-2021, 10:51 AM.
                        Loring in Katy, TX USA
                        If your only tool is a hammer, you tend to treat all problems as if they were nails.
                        BT3 FAQ - https://www.sawdustzone.org/forum/di...sked-questions

                        Comment


                        • #14
                          I have a few ZCTPs: my primary ZCTP gets used with my rip, crosscut, or combination blades when the blade is in the most common 90 degree position. It's a little worn these days so "zero clearance" doesn't exactly apply but it still works fine. I don't have tearout even with the small clearance (maybe half a millimeter each side or approx 1/64th of an inch either side?) Another ZCTP is for the Freud box joint set with a 1/4 inch wide blade opening. Parts of this ZCTP are wider to accommodate the 3/8s blade configuration. I use this blade set when making shop drawers using locking rabbet + dado joints so the ZCTP's main purpose is to keep workpieces from falling into the saw guts rather than minimizing tearout. And I have one rather chewed up ZCTP for the dado stack; it has multiple opening widths... The opening is 3/4 inches wide at the center when the blade height is fairly low (approx 1/4 inch or less which is the typical depth of rabbets/dado/grooves I make); there is a section 1/2 inch wide that was created when the blade was raised higher (to make large finger/box joints), and a section that is roughly 1/4 inch wide that jives with the blade raised to almost full cutting depth. I don't remember what I made that required such a deep dado/groove cut. The opening in that ZCTP is thus a series of stacked rectangles.

                          For bevel cuts I use the stock Ryobi throat plate. I have never tried making a ZCTP for use with bevel cuts... the Freud blades I use tend to make pretty clean cuts without the extra help offered by ZCTPs. I have screwed up a time or two and started changing the bevel angle while my primary ZCTP was installed and the blade jams quickly (saw not running) while setting the bevel. No surprise there.

                          mpc

                          Comment


                          • #15
                            Lchien, you are correct, tilting the blade into the zctp will make a much more desirable hole vrs just raising the blade….. just a typical brain fart in my post!
                            A tight fitting zctp does greatly close off your dust collection capabilities around the blade. If I am using a sled on the table saw I usually take out the throat plate completely to gain as much dust collection as possible. In our quest for better dust control I think we tend to seal the saw box too tightly. Regardless how large the dust collection line is to the saw box, if it is closed up tightly you might as well not even turn on the dust collector. When a blade tight zctp is used there is little air flow inside the saw box, thus allowing the blade to carry over sawdust and sling it out over the wood being cut. I noticed this after I sealed up the large blade angle adjustable slot in the front of the saw box with magnetic strips, and tested it with some of the strips removed. Results were noticeable.

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