Re: ZCI levelling (screws?)
There are several previous threads on this subject that can be found using the "search" function. In them you will find some good techniques and tips
1. Get some stock material that is close to the thickness of your existing insert. Depending on your saw, this could be 1/8" to more than 1/2". If it is too thick, it will have to be planed down, so a little less is better. Materials used are cabinet grade ply, corian counter top scraps, plastic, laminate flooring, MDF, etc.
2. Using the stock insert as a template, you trace out a blank insert on the material. Then rough cut it to dimension using the table saw, jig saw, band saw, etc. Then you finish the edges. A common practice is to use 2-sided tape (the carpet tape sold at Lowe's, HD, etc works well) to stick the existing insert to the material, and then use a router, with a bearing bit (pattern bit for a hand-held or trim bit for a table router). However, you can use a rasp, spindle sander, etc to final trim the curved edges.
3. At this point, You can rasp down the tab (if it had one), or just install a finish nail in the end to act as one, and also countersink a screw hole in for fastening. Some ignore this and just use the ZCI dropped into the recess. For ease of removal, you may want to drill a 3/4" hole through it in an area that the new blade/dado will not come through. I don't.
4. Then you need to get the insert level with the table top. At this point, you will probably have to remove the blade from the saw as most do not drop far enough below the table top. Some install set screws. I use layers of duct tape.
5. Now that it sets into the recess, and is flat with the table top, it is time to make it into a ZCI. That means running the blade/dado up through it.
For a dado set-up, stack the blades to the desired thickness, lower the cutters fully, insert the new blank, lock the fence over the blank far enough to the right so the dado will not hit it, (If you did not install screws/tabs, you may want to clamp a 2 x 4 across the top instead of using the fence), turn on the saw, and SLOWLY raise it up through the blank until it it higher than the cut you intend to make.
For a full-sized saw blade, its a bit trickier if the blade does not drop down far enough to install the insert. All else being the same as the dado, I do the first cut with a 7 1/4" circular saw blade (same kerf as the blade I am making the ZCI for). If it is full kerf (1/8") you can use one of the outside cutters from the dado set (the dado will be smaller than the 10"). After the initial cut having been run all the way up, then install the 10" blade and do it again. This is the technique for making one for a bevel cut as well as just for vertical. Some cut a dado half-way through the bottom of the insert blank where the blade comes up with a router, etc to eliminate having to use this 2-step approach.
As you can see, there are many techniques and materials, all of which work. If you do most of your cross cuts using a sled, the ZCI is not needed except for ripping thin strips. For dados, I, too, write the chipper/shim combo on the bottom, especially for the common off-thickness "1/2" (7/16 or 15/32) and "3/4" (21/32 to 23/32) ply
I usually make up a batch at a time (I have a TS3650 with a 1/2" thick insert, so I can make 18 out of one quarter sheet (2' x 4') of cabinet grade birch ply. That way I always have a blank on hand when I need a new one. Others have spent some time making a good quality insert into which they can screw a 1/4" thick 1 1/2" x 12" strip that becomes the new ZCI without removing the basic insert and eliminates the 2 blade step in cutting through it. That is on my "to-do" list when I get around to it
Guess this wasn't so short. Hope this helps, Hawk
Last edited by Gofor; 01-07-2010 at 12:28 AM.
Practicing at practical wood working