ZCI material

[JPG]

OK so thee rabbeted it.

[stihlsawer]

I like the extra strength in the middle. Nicely thought out!

[SteveMaryland]

I am looking at the CAD model of this ZCI. Buckeye Dennis, are you using CNC to fab this ZCI?

I think Shopsmith sells a plastic ZCI, but a well-designed and precisely cut wooden ZCI, made of oak or birch (or maple), would be very good to have.

I could never make such ZCI's on a Shopsmith and have any two of them come out geometrically identical.

[BuckeyeDennis]

I‘ve only made the one of them so far. I cut out a rectangular blank on my 520, and roughed the outside radius profile on the SS bandsaw. I cut the perimeter to final shape on my SS router table. For that, I used a factory insert as a template, bolted it to the blank through the mounting-screw holes, and made the cut with a pattern bit. For the perimeter rabbeting, I used a rabbeting bit in the undertable router. And IIRC, I used the OPR with a fence to extend the rabbeted area further into the interior, where required. The slot was also cut using the OPR and a fence.

That was all before I had a CNC. Nowadays, I could batch these things out quickly, easily, and very accurately, with about the only labor required being to mount the material and change router bits. If, that is, you don’t count the many months of learning curves on the CAM software and the CNC!

[edflorence]

I could never make such ZCI's on a Shopsmith and have any two of them come out geometrically identical.

Steve;

I think Buckeye Dennis has pointed out the key to making a batch of identical zci's, which is to use the factory insert as a template. First, use the factory insert as a pattern when laying out the shape on your zci material, then cut out that shape to within an 1/8 or less of the line using whatever works. I like the bandsaw. For the next step I vary a bit from what Dennis does. Instead of using a router to get to the final shape (which, don't get me wrong, is a great way to go) I made the pattern sanding setup that is shown in the sanding chapter of PTWFE and used that and a sanding drum, with the SS in drill press mode. After the blanks are cut to rough shape, I attach the factory insert to the blank with double sided tape and sand away that final 1/8 inch. Drill and countersink the mounting holes while in drill press mode, then go back to table saw mode, insert a blank zci, tilt the table if for an angled zci, and slowly raise the blade through the blank. I then write the angle on the zci for future reference. The result is that you can wind up with as many "geometrically identical" blank zci's as you want.

[SteveMaryland]

Thank you edflorence. Stacking and batch-cutting the raw blank material using double-sided tape would get the perimeter cut uniformly. As for the rabbet, the setup as illustrated in PTWFE Fig 18-14, page 229, would work but quite a lot of sanding.

Probably I would fab a router template to both hold the blank and edge-guide a router to cut the rabbet (I have no setup for routing directly with the Shopsmith).

In any case, the desired end-product would be a very rigid and well-fitting ZCI (or any other custom cutout) that can be replicated in quantity and also be disposable.

[BuckeyeDennis]

It's probably worth noting that using a ZCI on a Shopsmith is a little trickier than it is on a conventional table saw, due to all the adjustments available on a Shopsmith. You can't just switch over to table saw configuration, drop in the ZCI, and expect it to remain zero-clearance.

Here's the ZCI-installation procedure that I finally settled on:

• Before moving the table into position, remove the table insert. I do this even if the ZCI is already installed, because otherwise, when lowering the table it's dang hard to see when the blade is aligned with the slot.

• Unlock the quill, allowing it to fully retract.

• Move the table into position, with the blade slightly left of center in the opening, and tighten both the carriage and the table-height locks. For square cuts, best practice is to tie the main table to the extension table at this point.

• Drop the ZCI slot over the saw blade.

• Extend the quill enough for the insert to fit into the table cutout, and lightly lock the quill.

• Install the ZCI mounting screws.

• Unlock the quill, and fine-tune the quill extension while rotating the blade by hand. When the teeth just barely kiss the sides of the ZCI slot, tighten the quill lock.

After doing it a few times, this process becomes second nature, and requires very little extra setup time. There are other ways to skin that cat, of course. But if you don't fine-tune the blade position to the ZCI slot one way or another, you're likely to be making a LOT of ZCI's!

[edma194]

Ok, 12 mm. I rabbet around the bottom perimeter so that the top surface is flush with the table. The extra material remaining in the middle keeps it nice and stiff.

The slot fits either the blade guard or the non-through riving knife.

I like this approach. I want a ZCI for my Sawsmith 2000. Unfortunately the inserts are about 1/8" thick steel that is a flush fit all around the edges of the opening. There is a space in the center though and maybe I could mill something that is only 1/8" on the sides and sturdier in the middle.

[MrPerfect]

I haven’t seen it mentioned in this thread yet but here’s a YouTube video showing how to make them https://youtu.be/0SfNNlc6a_E

[stihlsawer]

Thank you for the link. Mike is extremely knowledgeable and one of many Shopsmith experts.