Zero Clearance Inserts, are they any good?

  • Advertise with us

« back to Power Tools, Hardware and Accessories forum

Forum topic by MrRon posted 10-06-2012 07:39 PM 1404 views 0 times favorited 19 replies Add to Favorites Watch
View MrRon's profile


4718 posts in 3209 days

10-06-2012 07:39 PM

If you have ever used a zero clearance insert (ZCI), I’m sure you have noticed, after using a few times, the kerf cut in the ZCI has grown wider. This happens because there is runout at the arbor and magnified 5x at the tip of the blade; this is unavoidable. The blade, due to runout, “wobbles” and makes the kerf in the ZCI wider than the blade tip. This is compounded when thin kerf blades are used as they can deviate easier. A dull blade will compound the problem even more. That being the case, I can’t see where ZCI’s are effective. I used to make ZCI’s for my saw, but after a few uses, I couldn’t see them giving me a better cut, so I don’t bother with them anymore.

19 replies so far

View Fred Hargis's profile

Fred Hargis

4954 posts in 2459 days

#1 posted 10-06-2012 07:44 PM

Ron, I don’t use one for a cleaner cut. Rather, it’s to keep small cut off pieces from getting trapped between the blade and the insert, or to keep them from disappearing altogether, which is what usually happens to me if that small piece is the one I need to keep. That said, my ZCI has replaceable wear strips made of 1/4” plywood or hardboard. That’s only a slight improvement over replacing the whole thing. But your point is taken: if you have for a cleaner cut, it needs frequent replacing.

-- Our village hasn't lost it's idiot, he was elected to congress.

View teejk's profile


1215 posts in 2650 days

#2 posted 10-06-2012 07:54 PM

they come into play when doing fine-tuning on a board where the cut-off piece wants to drop into the outboard side of the blade. tendency is for the piece to drop down (as opposed to becoming air borne) but it can be scary because it does flop around and make a lot of noise and some people might try to grab the piece…that would be bad…

View Tedstor's profile


1643 posts in 2598 days

#3 posted 10-06-2012 07:59 PM

Yep. I replaced my stock insert with a Leecraft. Being adjustable, it fits into the table better. The stock insert also had a GIGANTIC slot. Maybe 3/8-1/2”. Workpieces would occasionally get hung up in the slot. ZCI has eliminated that problem.

View OggieOglethorpe's profile


1276 posts in 2076 days

#4 posted 10-06-2012 08:03 PM

I count on my sled floors to create the zero clearance support for crosscuts. If the kerf wears, which takes quite a while on my current saw, as well as my previous cabinet saw, I drop an MDF subfloor in, and/or clamp an MDF “liner” to the fence. Both items can be slid back and forth for many fresh edges before they need to be tossed.

I do use zero clearance inserts for dados and rabbets when I’m using the rip fence, and with dual blade tenon setups, and find they last a long time. I designed them to be reversable, each insert works with two sizes.

One of the big benefits I see is help aligning the cut.

View toolie's profile


2120 posts in 2594 days

#5 posted 10-06-2012 08:07 PM

if you’ve got enough runout to widen the kerf in a ZCI to the point where it’s evident, i’d think there was a problem with the saw’s arbor.

-- there's a solution to every just have to be willing to find it.

View Bill White's profile

Bill White

4903 posts in 3926 days

#6 posted 10-06-2012 08:09 PM

ZCI all the time except miter angles or dado cuts. Just the way I do it, and I still have all my digits (so far).


View Howie's profile


2656 posts in 2889 days

#7 posted 10-06-2012 08:11 PM

I think Toolie nailed it.

-- Life is good.

View MrRon's profile


4718 posts in 3209 days

#8 posted 10-06-2012 08:16 PM

I do use a ZCI, but I don’t bother replacing it when it gets worn. Like you, I use it only to keep small pieces from getting lost. The purpose of my post was to inform that a ZCI shouldn’t be relied upon to guarantee a clean cut. I should have mentioned it’s real value was to keep small cutoffs from disappearing.

The real thought I was trying to convey was: there are several companies who make and sell ZCIs, some quite expensive. I just don’t want people to think, they must have a ZCI when it doesn’t do what it is touted to do, and besides they are so easy to make, any WW’er worth his salt can make one. Even the ones you buy still need to be cut and fitted by the user. So save that $30 and buy something you really need.

View Tedstor's profile


1643 posts in 2598 days

#9 posted 10-06-2012 08:25 PM

I dunno. I’m sure I could make a ZCI if I wanted to, but I doubt it’d be as good as the two Leecraft ZCIs I have. I paid less than $20 for mine. I dont think my time would have been better spent trying to make one of the same quality.

View MrRon's profile


4718 posts in 3209 days

#10 posted 10-06-2012 08:27 PM

That’s what I said in my original post. Runout, no matter how small, gets magnified at the blades tip. Some saw have a small amount of runout, some have a large amount of runout. There isn’t much one can do about runout, but a ZCI won’t help. As an example; a runout of ±.001” at the arbor will give a runout of ±.005 at the tip of the blade. A blade with a .125” wide tip, will leave a kerf that is .135” wide. Not much in woodworking terms, but this just serves to illustrate the effectiveness of ZCIs. It will keep small cutoffs from disappearing, but it won’t guarantee a clean cut.

View JarodMorris's profile


167 posts in 2341 days

#11 posted 10-06-2012 09:19 PM

If you want to get a clean cut, especially on plywood, use a cross-cut sled, start with the piece past the blade and the saw blade only going in 1/32” or so. Pull the sled back towards you and you’ll have an extremely clean cut on the bottom side of the plywood. Now, with the piece on what is usually the starting side, raise the blade to cut the entire piece and make the cut. No issue with tear out on the bottom of the plywood. I saw a video of this on Matthias Wandel’s youtube channel. I’d never heard of it before and it works great.


-- Dad: Someone was supposed to pick up his toys! Son: My name isn't "Someone".

View Charlie's profile


1100 posts in 2252 days

#12 posted 10-06-2012 09:34 PM

This reminds me I need to make a new ZCI. I aligned my saw and now the ZCI isn’t quite right. It’s ok….. but I like the look of a new one :)

View GarageWoodworks's profile


531 posts in 2122 days

#13 posted 10-06-2012 10:00 PM

Your zero clearance insert kerf getting larger probably has less to do with runout and more to do with you not returning your blade to 90.0 degrees after angle changed (assuming u use a different insert for angled cuts). The old slap a square against the blade isn’t good enough and the small angle errors (from 90) will result in your kerf getting larger.

-- Subscribe on YouTube:

View NiteWalker's profile


2736 posts in 2543 days

#14 posted 10-07-2012 01:41 AM

I’ve had the same zci in my tablesaw for MONTHS now, and it’s no worse for wear. Yes, the kerf opened up a tiny bit, but I still get no tearout on plywood or splinter prone woods. As already mentioned, I would be checking alignment of your saw; something’s not right.

FWIW, I also use the leecraft ZCI’s. Making my own I’d use baltic birch plywood.

-- He who dies with the most tools... dies with the emptiest wallet.

View gfadvm's profile


14940 posts in 2656 days

#15 posted 10-07-2012 03:04 AM

I’m convinced that even my well worn ZCI results in cleaner cuts and definately keeps those cutoffs from getting trapped between the blade and the insert. I use it for all through cuts except miters.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

showing 1 through 15 of 19 replies

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics