ZCI Interchangeable Inserts.

Boys and Girls,

ZCI is an acronym for Zero Clearance Insert, however, consider yourself pardoned when I say "ZCI Insert" and you accuse me of stuttering.

While toying with some comments on ZCI, Marpel enticed me with this titillating comment, "… rather than replace the full zci, the hardboard strip could be slid out and a new one inserted… ", … to me it was an,

an open invitation into action..

Took up the gauntlet and the inevitable happened,

which eventually rolled off the production line,


Using my dowel alignment lamination technique







created a "2 part" ZCI (compared to my standard ZCI),


The slit in the bottom layer,

was cut out so that the ZCI could be placed in the tablesaws throat to "fit over" the saw blade at its lowest point.

Cleaned it up (more later), locked it in and raised the blade…. Oh crap… the raised blade split the back of the insert letting it flop loosely,

Tried to salvage the ZCI by extending the insert slot and doctoring a new insert so it could be extended past the back exit point (leaving a gap at the front),

Unacceptable… and this version was quickly red crossed.

Back to the drawing board and extended the insert so that there was some substance at the end and the exercise was repeated,
Let's discuss some of the details in the build.

I made two versions,

1. To accept standard blades ranging from 1.7mm to ¼",
   
2. To accept dado stacks (up to 7/8") and standard angled blades,
   

Along with the above two plates, I made several inserts for each.


The dado width allowance had to be curtailed due to the position of the front anchor. After assembly, I concluded that drilling through the insert should not be a problem, so the next version (if required) will accommodate wider dados.

The ZCI plate was anchored at the back by the use of a fender washer,



and the standard countersunk bolt anchor at the front,

You may notice the finger hole and the don't drop that bloody screw "mushroom" plug,

to prevent this,

it's not a big hole, but a bloody small screw…

Because extra inserts need to be made and I didn't want to use the ZCI as the vehicle to feed it through the drum sander (as for the initial thicknessing), I made this jig up






that is the same thickness as the ZCI plate… and trust me, it renders the correct height for a new insert to get slipped in and be flush with the tabletop.

The jig was also used to give a better reference for flush cutting the alignment dowels and a larger level sanding surface,

I had to mark the down side of the jig,

as wrong orientation through the sander thins out the slider part of the insert. After stuffing up twice, writing "down" was easier than making new jigs.
The jig was also used to buff the top face of the inserts,


The parts were tunged and then buffed to a smooth top finish,

The large kerfed one was clamped down, though clear of the blade, and the blade raised,

and after removal of the "clamps", the MJ Splitter inserted on the insert,


Though still experimental and not tested for durability, I 3D printed some MJ Splitter look alikes for 1.7mm kerfed blades,






I was happy to wrap up this exercise, however, the tear out from raising the blade, though minimal, annoyed the crap out of me.
After a restless nights sleep and hesitation to sacrificing a board, I came up with a jig to hold a ZCI for the ZCI while raising the blade and not waste usable timber (albeit pine).
The jig held down another smaller insert,



and held "flipside" to the tabletop using mag-switches,




The blade came up throught the ZCI insert and the jig without any tear out,


a completely successful exercise.

Unfortunately, having fuctional pre-existing ZCIs, these new versions were deposited in my archive store house,

to be resurrected as soon as I stuff up the current 5 year old one… hmmm?

Again I splurted through another couple of animal nightie video.
Due to complaints by viewers that kept running out of beer, I have split the video into Part 1 and Part 2. They were followed up by an extra (Part 3) about the ZCI for the ZCI Interchangeable Insert.

The hero of this project is the concept and not the laser. If you're alread guilty of making your own ZCIs, this should be doable with conventional tools in case you happen to have misplaced your laser ot CNC.

Keep safe, jocks... and your jocks, safe!

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Next post day after thought.

A dovetail sliding insert could be a viable option if making with conventional tools out of solids.

However, in MDF, I believe my two piece laminated insert is more cost effective (time is money) when I consider accurate router setup vs. glue up…

I can imagine issues if the dovetails are too lose or too tight.

Proof is in the pudding, however, I do not plan to visit the kitchen soon… except for eating… and casko-vino replenishment.