how long do your zero clearance inserts last

[Robert Reece]

I make my ZCIs for my tablesaw out of gray pvc. Works great, but I find over time the slot widens slightly (not sure why really as I don't make abusive cuts where the blade would be getting wrenched around).

Do other people find this happens too?

[glenn bradley]

The widening of the slot is obviously caused by an altering blade path and the carrying of debris along the blade path. I don't think you have to be abusive to experience that. Variances in the material can contribute along with other things I can only guess at.

I use 1/2" BB ply and mine last a couple years with some widening over time. Maybe 1/32" of slop to either side is about when I call them "done". I have a 1-3/4HP saw and run thin kerf blades. I am under the impression that a higher powered saw with a slightly thicker blade would experience this less although I do not know this from personal experience. Cabinet saw users, what say Ye?

[johnny means]

I have never seen a ZCI that stays perfectly fresh for long. It usually is not a big deal, but sometimes I do like to freshen them up.

Instead of making new ZCIs I glue in a strip if matching material and bring the blade up through it again. I have also used plastic laminate on the surface of my inserts, which can be peeled and replaced when the slot gets a little sloppy.

[Tom Hammond]

I still have the same ones (two saws) that I made when I bought them... over 20 years ago.

[Tom Esh]

Completely normal. Even if the blade never rubs the insert, the dust does.

[Paul Douglass]

I have read that Corian makes a good ZCI. Anyone use it?

[Steve H Graham]

Until I forget what I'm doing and raise the blade through it at an angle!

[Trent Shirley]

I have read that Corian makes a good ZCI. Anyone use it?

I have wanted to make a ZCI out of Corian but have not been able to find a piece to work with.

My thought was to make the main plate from Corian and small inserts out of BB so just the insert can swap out. Uses a lot less material and makes replacement inserts a lot easier to make.
I had seen an article where someone made a plate out of aluminum for this purpose but figure the Corian would be a lot easier to machine.

[Tony Bilello]

I usually use MDF or Baltic Birch with plastic laminate on top. They get quite a bit of usage and last several years. Unless I see signs of edge break-out, I dont throw them away and edge breakout is generally not a problem making dados' if the blades are sharp. When using a finger joint jig, I use a backing board of 1/4" Luan scrap which sees 2 cuts before I shift to a new 'slot' behind the fingers.
ZCI's are good for what they do but are now substitute for a poor or worn out blade.

[Kevin W Johnson]

I'm going to be making myself one out of Corian soon, and the replacable inserts for it sound like a excellent idea.

I drove acroos Virginia a couple weekends ago to pick up a hefty amount of Corian scraps that Keith was gracious enough to give me. I've already made a few pens with it, and a sled for my bandsaw. I should have a table saw sled done soon too.

[Jay Allen]

I have never tried the corian thing because of the following reasoning, which is my own, comment as you wish..
To make a ZCI, you obviously have to cut through the insert with the "matching" blade. That's all fine and good, up to the point of "what blade are you doing this with?" As a general rule ZCIs are used in cross-cut applications, especially with veneered plywood. I use a Hi-ATB for that....and I absolutely refuse to run my Hi-ATB through Corian (or any other SS material). That stuff is hard and abrasive, it knocks the "sweet" off of the sharpness. Hi-ATBs have very sharply angled points which are easy to damamge. This damage, tiny though it may be, hurts the performance of the blade. I don't want to do the greatest damage to the cut quality of my blade in the first few seconds of use.
Ideally, all of the Solid Surface materials should be cut with a Triple-Chip blade. The teeth are much more robust, square alternated with 45 degree "dog eared" tips. They stand-up to the toughness of the Corian much better.
I make mine from BB ply.

[Neil Brooks]

I bought some UHMW cutting boards, to make a few ZCIs out of.

My go-to's have been from bb ply, and -- though the slots don't seem to change much -- my anti-kickback pawls DO like to dig into the ply, munching it up pretty good, over time.

[Myk Rian]

Fill the widened slot with epoxy and let it set.
Run the blade through it for a fresh slot.

[Charles Lent]

I have made ZC inserts from Corian, PVC, HDPE, MDF, UHMW. and Baltic Birch. Although Corian, UHMW, PVC, and HDPE look and feel nicer than Baltic Birch, none of them seems to last or perform significantly better than the rest for me, so I've just resorted to making them out of whichever material I have available. I do prefer one of the plastics for regular use and tend to keep a few un-cut Baltic Birch blanks available for making the occasional one-time use special angled cut or dado inserts that will likely never be used again. I always write the blade information on the bottom side of the inserts with a black marker so I can keep both the insert and the blade matched together, but eventually they all wear out and need replacement anyway.

Charley

[Noah Katz]

If the main purpose of a ZCI is to prevent tearout, it seems to me that it doesn't matter if the slot widens a bit, what you'd want is an insert with a moveable front part that could be advanced toward the blade when necessary.

One of the projects on my lengthy list is to make an aluminum throat plate with phenolic inserts that do just this.

[Todd Hyman]

If the main purpose of a ZCI is to prevent tearout, it seems to me that it doesn't matter if the slot widens a bit, what you'd want is an insert with a moveable front part that could be advanced toward the blade when necessary.

One of the projects on my lengthy list is to make an aluminum throat plate with phenolic inserts that do just this.

Interesting idea. Please post this when you finish this and also can you document how you built it?

[John Baum]

I made one years ago for the Sears 10" saw I bought 40 years ago when I bought my house. The insert recess is slightly less than 1/4" deep. I used hardened Masonite and eased the edges with the rip fence until the insert fit properly. It has lasted me for 10-20 years, but probably no longer qualifies as a zero-clearance, just a much narrower clearance insert than the steel one that came with the saw.

John

[Noah Katz]

Interesting idea. Please post this when you finish this and also can you document how you built it?

Yes, but it's been on my list for years already

[Bruce Moir]

A couple of years ago I put down some of that engineered flooring in my house. It is tough stuff and I noticed about the same thickness as my insert. I saved a few scrap pieces and cut to fit my saw. Still working great. On my new Delta TS the flooring material is a little thin so I added 4 screws to the bottom to raise to make level with table. My "engineered" inserts take the abuse, are easy to make - I cut with a jigsaw and smoothed edges on router table - and cheap to replace though I haven't replced one yet.

[Eric DeSilva]

Interesting idea. Please post this when you finish this and also can you document how you built it?

http://www.amazon.com/Betterley-Tru-Cut-Insert-System-Unisaw/dp/B0018Q6644/ref=sr_1_5?ie=UTF8&s=hi&qid=1291413041&sr=1-5

I got one of the Betterley's as a present; is that what you are thinking of doing? Got knows I'm sure you could do it cheaper than what they charge. That said, it is nice in the respect that it is dead easy to make replacement plates when they are nice and rectangular....

[Noah Katz]

I got one of the Betterley's as a present; is that what you are thinking of doing?

I was going to a modified version of a throat plate with a dovetail cutout, so to change an insert you just lift the front and slide it out.

I always thought the Betterley would be too fussy in having to deal with screws/tools.

But as you say, rectangular is easy to make and screws would be needed (or something more clever but too hard to make, a springs retainer) to do the adjustment.

Thanks for the brain jog, more thinking needed.

Actually if you made your inserts shorter with slotted holes you could do it with the Betterley.

[Cody Colston]

If the main purpose of a ZCI is to prevent tearout, it seems to me that it doesn't matter if the slot widens a bit, what you'd want is an insert with a moveable front part that could be advanced toward the blade when necessary.

One of the projects on my lengthy list is to make an aluminum throat plate with phenolic inserts that do just this.

For me, the main purpose of a ZCI is to prevent thin pieces from falling through or getting trapped between the blade and the insert. In that regard, the width of the slot is very important.

Tearout is generally not a problem with a sharp, purpose-built blade.

[Karl Brogger]

Tearout is generally not a problem with a sharp, purpose-built blade.

Exactly.

Except in Melamine. A zero clearance insert is junk in no time if you want a chip free cut. It has to be tight where the blade comes into the plate, and that doesn't last long.

[Salem Ganzhorn]

I have one in my saw now. It works pretty good. Not sure it is any better or worse than high quality ply.

The positives: slick, flat.
The negatives: doesn't tap as good as ply, harder to make a perfect non-wiggly fit (for me) because it does not compress.

[Scott Hildenbrand]

Here is what I did and it works out well. Though I'm going to make a new main insert out of wood later. The UHMW plastic has too much flex slop in it at the center.

http://photos-c.ak.fbcdn.net/hphotos-ak-snc3/hs127.snc3/17442_1311597277601_1460724611_30824281_7791629_n. jpg
http://www.sawmillcreek.org/showthread.php?t=131225

The inner ZCI slip insert is made out of some Pergo laminate flooring that I had left over. MDF core and basically plastic laminated. Really slick stuff.

Once I get the wood insert done I'll be a truly happy camper.