Introduction: DIY Zero Clearance Table Saw Insert

Picture of DIY Zero Clearance Table Saw Insert

Making thin cuts on your table saw requires a zero clearance insert so that the stock doesn't get pulled into the table saw after cutting.

Most table saws have an insert that's good for a most applications: it can accommodate the blade at full height, at any angle, and has space around the blade that allows sawdust to be pulled down from either side of the blade. A zero clearance insert has no clearance around the blade, and should only be used when the blade is perpendicular to the table. Making your own zero clearance insert is easy, and we can even use the table saw to make it! Having one on hand is great for the few times you need the right tool for the job. To make this zero clearance insert I used

Because there is zero clearance between the blade and the insert there is no space for sawdust to be pulled away from your cut, however this is an easy compromise since without a zero clearance insert you would not be able to make thin cuts.

Ready? Let's make!

Step 1: Take Measurements of Insert

Picture of Take Measurements of Insert

Remove your table saw insert and take the overall measurements: length, height, and depth.

To get accurate readings I used digital calipers. Make sure your saw insert housing is clear of sawdust so you can get the best readings. Most saws have height adjustment screws so you can level out the insert after if your readings are a little off, but it's better to get accurate measurements before starting.

Step 2: Trace

Picture of Trace

The scrap plywood I sourced was roughly the same thickness as the existing insert, about ⅛". There are height adjustment screws in the insert housing that allow the insert to be raised and leveled a little, so as long as your scrap plywood is within this threshold you should be fine.

Place the stock insert face-down on the plywood and trace the outline with a pencil. There's no need to trace the blade slot, since we'll be cutting that out later.

Step 3: Set Fence + Rip Cut to Width

Picture of Set Fence + Rip Cut to Width

Set your fence to the width of the insert, raise the blade only slightly higher than the plywood stock you're using, and then rip the plywood with the overall width.

Setting a table saw fence accurately before you cut is critical to get accurate and consistent results on your table saw. Setting the fence is a topic covered in the free Table Saw Class - Meet Your Table Saw, check it out if you're unsure about your fence accuracy.

Step 4: Mitre Cut to Length

Picture of Mitre Cut to Length

Once you have the plywood ripped to the right width it can be cut down to the right length.

Cutting long pieces on the table saw requires a mitre cut. Mitre cuts are made with the mitre gauge and need to have the fence moved away so it doesn't interfere while cutting.

Set the mitre gauge to 0° and place the ripped stock against the back of the mitre gauge, lining the traced outline of the insert edge with the blade. The mitre cut doesn't need to be right on your trace line, since we'll be refining the cut by sanding in a later step. This mitre cut is just to trim down the length into something more manageable.

Use the mitre gauge to cut both ends of the plywood to trim up the outline.

Step 5: Angled Mitre

Picture of Angled Mitre

To make the sanding process easier, material was removed from the corners of the plywood by making angled cuts on the mitre gauge - follow the link to learn how to make accurate angled mitre cuts.

The mitre gauge was set to 45° and the traced plywood was placed in the mitre gauge with the end to be cut trailing the mitre gauge. Corners were cut, and the mitre gauge was moved between the two mitre tracks so that every cut was trailing the mitre gauge and not leading it.

Step 6: Sanding

Picture of Sanding

To round off the corners of the plywood a powered sander was used. Almost any type of sander can work for this application. Since I don't have a stationary sander I made do by inverting my belt sander and clamping it to the workbench.

With the belt sander secured to the bench the trigger can be locked on and allow sanding with both hands without holding on the sander.

The corners of the plywood were sanded down right to the traced outline of the insert. Since the trace was alightly larger than the insert I knew I could sand very close.

After power sanding I cleaned up any rough spots by hand sanding with fine grit sandpaper.

Step 7: Test Fit

Picture of Test Fit

Before packing away the sanding equipment see if the sanded insert fits in the table saw housing.

Some table saws have irregularities inside the insert housing, you can see if this applies to you by turning over your stock insert and seeing if there's any special clips or cutouts. If there are any, see if you can mimic them on the underside of your zero clearance insert to make a snug fit.

Since this style of insert is very minimal it's unlikely that there will be any interference from the housing you need to worry about. With the sanded insert in the housing check to ensure a good snug fit, sand away any areas as needed to get the fit you want.

Step 8: Clamp Insert in Place

Picture of Clamp Insert in Place

Fully retract the blade and place the insert into the housing. Lay a sacrificial board over the saw table and directly over the insert, and then clamp in place.

Start the saw and slowly raise the blade fully, cutting through the insert and the sacrificial board.

The board will keep the insert in place while the zero clearance kerf is being cut. While the saw is still on, lower the blade completely and then turn the saw off. Remove the sacrificial board and check out the cut in your insert.

Step 9: Drilled Opening

Picture of Drilled Opening

To make the zero clearance insert easier to install and remove a finger hole can be drilled. Using the stock insert as a guide for placement, I drilled a ¾" hole in the plywood insert.

To reduce tearout I drilled the hole with a sacrificial board underneath the plywood insert.

After drilling the opening the edges were smoothed out with sandpaper.

Step 10: Install

Picture of Install

The zero clearance insert is ready to be installed and rip thin stock without fear of thin strips of wood being sucked into the saw.

Even though the zero clearance insert doesn't allow for sawdust to be extracted I still use the vacuum on my table saw as the suction pulls the zero clearance insert down into the saw and keeps the insert firmly in place. My stock insert has a clip on the underside that helps hold it in place, but this zero clearance insert doesn't require it when the vacuum is on.

To keep the zero clearance insert operating as it should make sure the blade is of the saw perpendicular to the table, this will keep the clearance as minimal as possible and prevent any thin stock from being pulled into the saw.


have you made your own zero clearance insert from this Instructable? I want to see it!

Share a picture of your version in the comments below and get a free Pro Membership!

Comments

bmcnabb made it! (author)2017-04-16

My saw insert isn't as nice of a shape but, I did make a replacement for it and I can't recommend doing this enough. Makes a HUGE difference when trying to cut small pieces. Thanks!

FN64 made it! (author)2017-03-30

I fashioned mine from a scrap of laminate flooring. I cut it out with a router and a flush trim bit. It was too thick, as is, so I routed the sides down and kept testing till it was flush with the table. It fits snugly in the cutout and works like a charm.

mikeasaurus (author)FN642017-03-30

That insert looks extra stylish, since it's from flooring :)

Thanks for sharing, enjoy the Pro Membership!

FN64 (author)mikeasaurus2017-04-02

Thank you kind sir.. It's very much appreciated..

..FN..

seamster made it! (author)2017-03-27

Made from a really nice piece of scrap hardwood! :)

mikeasaurus (author)seamster2017-03-27

Wow, very nice scrap :) Thanks for sharing your insert, Sam!

myvoy made it! (author)2017-03-21

i make mine very similar but finish on router table. i make them in two parts because my inserts are very thin to give it more heft. thanks for sharing

mikeasaurus (author)myvoy2017-03-21

The extra heft and support is a great idea! Thanks for sharing pictures; enjoy the Pro Membership!

JGDean made it! (author)2017-03-12

Very good Instructable, but I think you missed a couple things. One of the advantages of a zero clearance insert is decreased tearout, especially when cutting plywood. You also have to remove the riving knife before you can cut the slot in the insert or use it. (It took me a minute to figure out why the insert was being pushed up by the blade - a blonde moment ) I also had to do some routing on the underside of the insert because my Kobalt saw only has 0.98" between the table surface and the adjusting screws and the thinnest stock I could find was 1/8" melamine board. (see second picture). It works fine, but I think I'll add some tabs to secure it before I use it very much.

mikeasaurus (author)JGDean2017-03-21

Thanks for sharing pictures of your build. Enjoy the Pro Membership!

FrancescoK2 (author)2017-03-12

Isn't it dangerous now without the anti-kickback protection?

Depends if the anti-kickback device is American or European in design. European riving knives are designed as part of the blade arbor mechanism, so they curve around the blade with approximately 1/4" clearance and move up and down with the blade height adjustments. American style riving knives are fixed in place, and therefore have to be removed in order to make any cut that doesn't go all the way through the stock. Plus, that makes them a fixed distance from the blade which is usually far enough back to create other problems. This is why many people end up taking them off entirely. Add to that, the "anti-kickback" pawls that are often part of the blade guard are, IMO, more dangerous than not using them. All the safety mechanism in the world are a poor substitute for proper technique. That said, I strongly advocate for well-designed safety equipment, the most important of which are proper technique and a clear head.

underground carpenter (author)2017-03-14

Warning: 1/8" stock, whether plywood, melamine, or tempered hardboard, has way too much flex in
it to be safe as an insert. You'll note that the factory made insert is made
out of steel. They didn't do that because it was the most economical
material to use. Even manufactured table saw inserts made out of
aluminum are usually at least 1/4-3/8" thick.

rsfluffy (author)2017-03-12

I know I'm missing something here but "zero tolerance"? That doesn't make sense to me. Are they just called that even though it's impossible?

What they mean by "zero clearance" is that the slot for the blade is just the width of the blade compared to the stock inserts that usually are about 3/8" to 1/2" wide to allow for the blade to be tilted. Obviously the blades are not exactly "zero clearance" since just the vibration of the motor (even in the best saws) causes run-out of the blade by a few thousands of an inch. I've been making these for almost 20 years, since my first shop saw was one that no one made inserts for. Now I even have inserts for my stacked dado blade in 1/8 inch increments as that gives me cleaner dados.

JamesB765 (author)rsfluffy2017-03-12

It's zero clearance, not zero tolerance. Those words mean two different things. A zero clearance insert is a term used in woodworking for one where you only have a minuscule gap between the side of the blade and the kerf on the insert. When you don't have the normal gap there, it gives more support on things like plywood, where the blade would normally chip the edges as it pushes the teeth down through the material.

stepinfech (author)2017-03-12

Very nicely Done. I have made these before but I always use a piece of aluminum & and a carbide tip blade to cut the slot. Nor sure if most people are aware but carbide tip blades with a table saw is a great way to cut this stuff. I have cut up to 1 1-2" this way

joe.lyddon.7 (author)2017-03-12

Have you tried using the Router with a flush-trim bit to cut the New insert from a rough-sized work piece and using the Original Plate as a guide taped to the Blank?

It's much easier than doing it this way... I think...

Chuck666 (author)2017-03-12

an easy way to make these inserts is using 3/8" Baltic birch plywood for the insert. Sabre saw/jigsaw the blank 1/8" larger and then use double face tape to fasten the original to the blank. Use a pattern router bit to finish it to a perfect fit. Because Baltic. Birch is so dense you can tap the set screw holes for adjustment screws. Fine tune as necessary.

gwlinn123 (author)2017-03-12

Thanks for sharing your incredibly detailed method of making zero clearance inserts. It seems hard to find the specific blank for a particular saw and they aren't very cheap. I only have one that I purchased and I could use about 6.

After seeing your article, I'm wondering if I can't make them with my 3D printer. It should also be possible to add the "hold down" clip. I will probably use Nylon as the print material for strength.

Also, my blade does not retract much below the surface of the insert. When I cut the slot in my "store-bought" insert, I had to dangerously hand-lower the insert to get the slot started. Then, I could use the board and clamp method you show. I think I could work around this problem, if necessary, with a 3D printed version by simply making the insert a little thinner near where the slot will be.

dumbau (author)gwlinn1232017-03-12

For the situation where the blade will not retract below of the insert before cutting, sumply use a smaller blades make the initial cut, like a 7-1/2" circular saw blade or one of your dado set blades for example. Then replace the blade you plan to use and finish raising the blade. If the circular saw blade is too narrow, you may need to mount 2 of them to make the initial cut. You just have the initial cut to be high enough so you can safely mount the full sized blade.

mikeed14 (author)gwlinn1232017-03-12

or you could use a router to make the area near the blade thinner.

gwlinn123 (author)mikeed142017-03-12

You are correct. Although I am still a "newbee" with respect to 3D printing, one idea is to make the part without much additional work. Since all 3D printers are not the same, I have found that dimensions are not always as specified. For example, hole diameters are often (for me, anyway) a little smaller than I specified. So, I often print a "test" piece where I do not commit to the whole part, just to some feature that I'm interested in to test the results.

With respect to "thinning" an area, that seems pretty easy to specify once you have somewhat mastered the CAD program used to generate the part. My first trial will be basically just the "outline" of the inset. That way, I can find out if my measurements are close enough. There's always the "is it English or Metric" question. For 3D work, I work in metric. But, older things, like my 30 year old Sears table saw, are probably English.

With 3D printing, as it seems to be the case with woodworking, the more you do, the better results you get. (So, can I live forever?)

bumbula (author)2017-03-12

I used a piece of plexiglass. To cut the zero clearance slot I reversed the blade. This reduced the amount of debris flying all over. I used a straight cut router to cut the rough shape and then sanded it down using fine sand paper for metal finishing.

gm280 (author)2017-03-10

I have made lots of them basically using the same technique. You can also use a router with a ball bearing and use the steel plate as a pattern. And you can use a lot of different materials as well. Plexiglas can be used as well.

Neowizard (author)gm2802017-03-12

Cutting the zero clearance slot in a Plexiglas with a table saw would likely shatter the Plexiglass.
Maybe if you use a Melamine blade. I don't think general purpose blades will be delicate enough.

gm280 (author)Neowizard2017-03-12

I actually cut Plexiglas on my table saw. While it does send Plexiglas particles all over the shop, It cuts surprisingly easy and smooth as well. I also cut Plexiglas on my 12" DeWalt chop saw as well. It too sends particles everywhere, no no worst then cutting wood. Just make sure you have eye protection on as you should cutting anything.

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