Zero-Clearance Inserts

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Blog entry by RexInMinn posted 10-12-2010 09:54 PM 1832 reads 0 times favorited 10 comments Add to Favorites Watch

What is the advantage of a zero-clearance insert?

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10 comments so far

View David Craig's profile

David Craig

2137 posts in 3102 days

#1 posted 10-12-2010 10:01 PM

A cleaner, chip free cut. More of the workpiece is supported and there is less gap where the piece could experience tear out due to the blade.

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-- There is little that is simple when it comes to making a simple box.

View dustbunny's profile


1149 posts in 3289 days

#2 posted 10-12-2010 10:04 PM

You can cut thin strips with support of the insert.
The insert keeps small and thin cuts from falling into the saw.


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View ocwoodworker's profile


209 posts in 2998 days

#3 posted 10-12-2010 10:17 PM

Imagine cutting a bundle of straw with a sharp knife. No matter how fast you swing there are always the last bit of straw that bends back from the blunt force rather then getting cut. It is the same with wood. Most cuts are end grain cuts (like a bunch of straws packed together). Those last set of grains are unsupported from anything behind it. So they just bend backwards (and take out part of your finished wood with it). A zero clearance insert solves this problem by creating a backing support that makes the back “straws cut clean rather then tear backwards.

-- I'd like to believe Murphy's Law haunts my woodshop, because if it's Karma it would mean I had something to do with it. - K.R.

View RexInMinn's profile


17 posts in 2777 days

#4 posted 10-12-2010 10:21 PM

I greatly appreciate your responses. Gonna have to try making one sometime. Is 1/8” hardwood stock normally used?

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View RONFINCH's profile


143 posts in 2918 days

#5 posted 10-12-2010 10:24 PM

1/8” is too thin. Mine are 1/2”, your table saw may dictate something different.

View longgone's profile


5688 posts in 3302 days

#6 posted 10-12-2010 10:26 PM

I use zero clearance inserts on my saw and have one for 90 degree cuts and one for 45 degree cuts. I do not know what you mean by 1/8” hardwood stock used. The zero insert is made the same thickness as your saw’s stock insert and replaces it because it must be flush with the table saw top to keep pieces being cut flowing smoothly on the top.

View Dan's profile


3630 posts in 2874 days

#7 posted 10-12-2010 10:37 PM

I recently made my first zero clearance insert for my Delta contractor TS. After seeing so many people talk about their benefit I thought I should add one. I made mine out of 1/2 MDF. Was really easy to do, just traced the steel insert, cut it out a tad larger with the jig saw and then attached it with double sided tape to the steel bit and used router with flush trim bit to finish the cut. Came out exact size.

The insert I made was a little thin once in place so to make a quick fix of that I just added some masking and duck tape until it was flush with the table top. Its been on my saw ever since and I do find that it works better. Other then the safety and support it also helps when cutting along a pencil line because the gap in the plate is right where your blade. Just makes it a bit easier.

-- Dan - "Collector of Hand Planes"

View SPalm's profile


5320 posts in 3875 days

#8 posted 10-13-2010 12:24 AM

They also look cool and it makes people think you know what you are doing.

Seriously, I use them all the time. Reduced tear out and added safety.
Make as thick as the original insert (or as close as you can). It needs to be flush with the top of the saw.


-- -- I'm no rocket surgeon

View Gofor's profile


470 posts in 3780 days

#9 posted 10-13-2010 01:11 AM

One problem you may run into with some table saws is that the blade does not go all the way down below the thickness of your blank insert. This is particularly true on inserts that are 1/2” thickness. There are several ways to address this.

Easiest way is to make your first cut with a smaller diameter blade of the same thickness as the blade you are making the insert for (yes, you need to make an individual one for both full kerf and thin kerf if you use both, as well as for all the different widths of dado stack that you normally use). For a full kerf blade, usually one of the outside dado cutters works fine. A circular saw blade may work for your thin kerf if they are the same thickness.

Another way is to route a 1/4” deep slot on the bottom side down the blade track.

Another way, but less accurate, is to stick the insert to the top of your stock insert with double sided tape and clamp a scrap wood piece across it front to back to hold it while you run the blade up through it.

There are other ways as well, which you will see if doing a search on “making a ZCI”. Some are safe and some are downright scary. (such as dropping the insert down on a running saw blade, which was (and maybe still is) described in one manufacturers’ owners’ manual).

Second major point is that if you have a 1/2” thick insert, “1/2” ply will be about a 32nd” to thin. You can easily shim it up with one or two layers of duct tape on the bottom where it rests. Some install leveling screws. Its your choice how detailed you want to get. I go quick and simple, and when I need new ones, knock out about 18 blanks out of 1/4 sheet of cheap cabinet grade ply. (I use the method that Dcase described). Some make one basic insert of a good hard material, with a 1” wide strip dadoed into the top, and just replace the strip with 1/4” ply when changing set-up.

If you have a saw with a 1/8” thick insert, most of the above does not apply. It will when you upgrade.

The last point is to remember that with a ZCI, you cannot adjust the bevel of the blade. If beveling the blade, you must remove the ZCI first, then bevel the blade, run it all the way down, and run it up through a new blank, or go back to your stock insert for bevel cuts.

Hope this helps


-- Go

View Rick's profile


9591 posts in 3026 days

#10 posted 10-14-2010 06:35 AM

To prevent “Tear Out” (If you REALLY need to), I make a 1/8” to 1/4” deep cut on the Bottom Side of the board I’m cutting. Bring the Blade up about 1/4” to 1/2” proud of the top of the board. Run it through again finishing the cut. NO Tear Out.

IF I need “0” Clearance, I find that the Blade MUST BE Absolutely Tight to the “0” clearance piece. I’ve tried a few of the “Custom Ones” for each type of Blade or Cut. Got tired of changing whatever needed to be changed for various types of Cuts, so I went to a Sacraficial “0” clearance piece of 1/4” Hardboard or an old piece of Panelling.

Double Sided Tape on the Underside to hold it to the Table. Set the Fence to the width of cut you want. Place the Sacrifial piece tight to the Fence and down onto the Table. Start the saw. Slowly bring the Blade up and through to the Height of Cut you require.

My Table Saw Blade will go completlely Under the Surface of the Table, so I don’t have a problem there. If yours doesn’t the Sacrifical piece can still be put in place but the saw must be turned on prior to Lowering the piece onto the Table with the Blade at it’s Lowest setting. Then turn your Saw off, Secure piece all around if needed. Saw on, then bring the Blade up to Cutting Height. NO. It’s not dangerous but exercise Caution as always.

Just remembered have an Old Jig Picture of that as below.
Zero Clearance 500x300

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