The jury is in on ZCI material

[Alan Schaffter]

Nobody is currently producing the WoodDynamics design- I believe it is available to anyone- I did an internet search and couldn't find any existing patents on it.

The Betterly Tru-Cut Insert system seems well built and if you use ZCI's regularly will pay for itself sooner than later. If there are any complaints against it they might be: you need to remove six screws to change inserts, if you can get phenolic or another rigid material it might be a bit harder to make your own inserts, there is an issue with certain types of splitters (MJ) and blade clearance (can't raise the blade full height), it doesn't fit all saws, and cost is $80 for the frame and $30 for a 4-pack of replacement inserts.

[Rob Young]

How will it open up if you are using the same blade all the time. Now I am not a contractor, just a hobbyist so that may make big difference.

Blade flutter is one way.

If you adjusted for an angle (using a different ZCI), then thought you came back to 90 but were just a smidge off.

You may think that ZCI isn't moving about in the slot but it is, just a little bit.

Getting a blade sharpened and re-using its old ZCI.

[Rob Young]

Some final thoughts:

I flip the insert over and get a second life from each one. Just wax the back side and tweak the levelers.

Never had much problem with the set screws in plywood. As mentioned above, a drop or two of CA down the hole and you can cut nice threads.

To start the slot for the blade I switch to one of the outside blades of my dado set but DON'T drive it all the way through. it only needs to come up about 1/2 way through the insert (just a couple turns of the crank) to cut sufficient clearance for my full 10" blades. YMMV

One way around the blade height versus bottom of insert problem is to just pass the insert over a straight bit on the router table and cut a groove. However this makes it harder to flip the insert later because now you have a groove on the top that can catch stuff. Fill it I suppose but now we are making a lot of extra work out of this ZCI.

[glenn bradley]

I've settled on 1/2 BB ply, 1/4-20 setscrews threaded into an under-size hole in the ply, flip for dual use, MJ Spliters, no failures. ZCI's are wear parts to me. They last till I do something that makes the offset inaccurate like re-align the saw, change things for a repeated operation, etc. I think I am on my 3rd set (one or two for each blade/operation) in this shop.

[Bill Huber]

Blade flutter is one way.

If you adjusted for an angle (using a different ZCI), then thought you came back to 90 but were just a smidge off.

You may think that ZCI isn't moving about in the slot but it is, just a little bit.

Getting a blade sharpened and re-using its old ZCI.

I guess the question is what is Zero clearance.

I just went out and checked mine, I put this one on in Oct. 2008 and you are right, it is not zero clearness any more. I can put a .009 feeler gauge between it and the blade on both sides.

But is .009 to much, will that really make a difference in the way my cuts come out?

In the 2 years I have been using this one I have gone back and forth from the rip to the the general blade and my plywood blade many times. I have cut a lot of angles and have had my general blade resharpened.

So I guess the bottom like is what is zero clearance to you.

[Alan Schaffter]

Some points to ponder-

• To reduce/prevent chip-out the only place you need zero clearance is at/around the (carbide) tips of the blade where they go down and re-enter the table.

• The clearance everywhere else doesn't need to be so tight since the only function there is to prevent big chips or slivers from wedging against the blade.

• A ZCI works against dust collection. Standard throat plates are only slightly better.

• If you have an enlarged, sloppy opening on your ZCI and it is made from a material that glue, epoxy, plastic adhesive, etc. will bond to (wood, phenolic, etc.) you can renew and return it to zero clearance quickly and easily. True up (and widen) the slot on your router table, then just glue in a strip of similar material closing the slot completely. Install the insert. Turn on the saw, and raise the blade to recut a new zero clearance slot. This can be done many times.

[Jim O'Dell]

I had been thinking about using corian myself but when I got a scrap piece it seems incredibly hard. Is it safe to machine in a planer to get the right thickness?

I have yet to find a source for scrap parts to make my inserts with. Just found the one small piece someone had laying around.

Trent, no need to plane it down. Just route a rabbit on the underside edge to the proper thickness. This will actually leave a little more meat to the ZCI to help keep it from breaking.
I used Corian to make a ZCI for my Ridgid contractor saw that has the replaceable inserts. It was a lot of trial and error getting it close to right. It works, but it's not perfect. And it is brittle. I've broken out the outfeed screw part of the Corian because it was too close to the outside edge. DSCN2735.jpg DSCN2736.jpg Still works though.
I tried the dovetail inserts like the the original unit used, but never could get the tolerance right. When I saw the Tru Cut unit (also sold at Infinity Tools, and we get a 10% discount there!!) I changed the design to match.
Of course now I have the new TS, and need to do something for it. Nothing available for it commercially (except for the Grizzly blanks at 30 bucks each!!) so I will need to make one for it. And I'm out of Corian!!! Jim.

[Alan Schaffter]

When I saw the Tru Cut unit (also sold at Infinity Tools, and we get a 10% discount there!!) I changed the design to match.
Of course now I have the new TS, and need to do something for it. Nothing available for it commercially (except for the Grizzly blanks at 30 bucks each!!) so I will need to make one for it. And I'm out of Corian!!! Jim.

Jim,

Something to try:

With a pin or lip on the outfeed end to prevent it from lifting, couldn't you use rare earth magnets rather than screws to secure replaceable inserts like used by Tru Cut? That would make it incredibly easy and lightning fast to change inserts- just pop it out and pop a new one in!! (Boy, sometimes my brain is firing on 10 out of 8 cylinders! )

You would only need a simple template to crank out additional inserts. If the main insert was ferrous, you could drill and glue or use cup mounts to attach the magnets in the replaceable insert. If you still use Corian for the main insert you could mount the magnets and flathead screws for the other half the pair in either part of the assembly. It may have been a cost issue, but I'm surprised Tru-Cut didn't do something like that.

[Jim O'Dell]

Jim,

Something to try:

With a pin or lip on the outfeed end to prevent it from lifting, couldn't you use rare earth magnets rather than screws to secure replaceable inserts like used by Tru Cut? That would make it incredibly easy and lightning fast to change inserts- just pop it out and pop a new one in!! (Boy, sometimes my brain is firing on 10 out of 8 cylinders! )

You would only need a simple template to crank out additional inserts. If the main insert was ferrous, you could drill and glue or use cup mounts to attach the magnets in the replaceable insert. If you still use Corian for the main insert you could mount the magnets and flathead screws for the other half the pair in either part of the assembly. It may have been a cost issue, but I'm surprised Tru-Cut didn't do something like that.

Good ideas Alan. On the Ridgid, the factory outfeed tie down is a piece of spring steel that just slips under the lip at the back. Easy to make at the factory, harder to reproduce by an amateur. So I drilled a hole in the saw's back ledge and tapped it for a screw. The Grizz saw will be easier to do.
The only problem I have with the ZCI I built is that the inserts aren't a perfect fit. Good enough to work, but not the same quality fit as you would expect in a store bought unit. A CNC router system would make it more professional looking. Easy to reproduce extra inserts with a template bit on the router table. I ended up using 1/4" MDF with laminate glued to it. Came up to the perfect height I routed my recess at. And slicker that the MDF would have been alone. It would be nice to have a screw holding the insert down at the side, but just not enough meat left in the Corian at that side to do it. I made mine where the inserts will do both regular blades and dados, thus the weird shape. Jim.

[Alan Schaffter]

A CNC router system would make it more professional looking. Jim.

I sent a query to my brother to ask him about making a Tru-Cut like throat plate from steel to hold rectangular inserts I will make (from plastic, Corian, phenolic, etc.) that are held in place with rare earth magnets.

He just got done refurbishing and converting a huge old Bridgeport mill to full CNC. While he mostly does aluminum, I think he can do steel, though it will be much slower. The experiment is worth his, er my time.

[Jim O'Dell]

Heck, I'd go ahead and use the aluminum! Jim.

[Alan Schaffter]

Heck, I'd go ahead and use the aluminum! Jim.

I really dislike woodworking stuff made from aluminum- it just doesn't hold up. I have scratches on my Unifence fence and rail. I have scratches and dings in the aluminum anodizing on my Woodpeckers router plate from the steel insert ring wrench hitting it. They wouldn't be there in steel. Wood doesn't slide on aluminum nearly as nicely as it does on steel.

[Glen Butler]

I am going to resurrect this old thread to say that you can tap MDF. What you need to do just before and after tapping is wick thin CA into the hole. Tap again. I usually wick CA twice and tap twice to get a good clean thread. I however do not like MDF for ZCI's; it's just too flimsy.