I rely on my table saw for everything from ripping and crosscutting boards to cutting dadoes, grooves, and rabbets. Whatever the operation, a clean cut is always the goal.
But even with a well-tuned saw and a sharp blade, you can still end up with chipped or splintered edges.
One of the simplest solutions is a zero-clearance table saw insert.
Unlike a standard insert with a large opening around the blade, a zero-clearance insert has a slot that closely matches the blade kerf. The insert supports the workpiece right next to the blade, helping prevent the wood fibers from breaking away along the cut.
Why Make Your Own Zero-Clearance Inserts?
You can buy zero-clearance inserts for many table saws, but making your own has one big advantage: it's inexpensive enough to make several.
And you'll probably want more than one.
A zero-clearance insert is matched to a particular cutting setup. Switch from a standard blade to a thin-kerf blade, for example, and the opening no longer provides the same close support. Different dado widths can also require different inserts.
So instead of making them one at a time, I usually make several insert blanks at once. Then I can dedicate them to different blades and cutting setups as needed.
Start with an MDF Blank
I use 1⁄2" MDF for the insert. It's inexpensive, flat, stable, and easy to shape.
Start by ripping the blank to width. You're looking for an easy slip fit in the table saw opening without noticeable side-to-side play.
Leave the blank slightly long at first.
Once the width is correct, place your saw's factory insert on top and attach it with double-sided tape. The factory insert now becomes a convenient template for shaping the blank.
WOODSMITH TIP: Make Several Blanks at Once. Once you've established the correct width for your saw, rip enough MDF for several inserts. Shape them all during the same shop session and you'll have spare blanks ready whenever you change blades or dado setups.
Rough-Cut the Rounded Ends
Most table saw inserts have rounded ends, and duplicating them is a simple two-step process.
With the factory insert still attached, take the blank to the band saw and remove most of the waste around the ends.
Stay slightly outside the factory insert. There's no need to cut precisely to the line because the router will take care of the final shaping.
Flush-Trim the Insert
Next, head to the router table.
Use a flush-trim or pattern bit to bring the MDF blank flush with the factory insert.
Your factory insert may have features that you don't want the router bit to follow, such as a retaining pin or a notch for the blade guard. Simply skip those areas during routing.
After removing the factory insert, sand away the remaining bumps and fine-tune the fit by hand. You're looking for a smooth slip fit without unnecessary movement.
Add a Finger Hole & Blade Guard Clearance
With the overall shape established, you can add the smaller details.
Start by drilling a 3⁄4"-diameter finger hole. This makes it much easier to lift the insert from the table saw.
You can also cut a notch for the blade guard as needed for the setup shown here.
Not every insert requires the same clearance. For example, an insert dedicated to dado work may be configured differently. That's another reason it's useful to make several blanks at the same time.
Add a Retainer
The insert needs to stay securely seated while the saw is running.
Use the factory insert as a guide for adding a retainer to your shop-made version.
The exact design can depend on your saw, but the goal is the same: prevent the insert from lifting out of its opening during use.
Make the Insert Flush with the Saw Table
A good zero-clearance insert should fit flush with the surrounding table saw surface. This isn't just about appearance.
If the insert sits proud, the leading edge can catch a workpiece as you feed it through the saw. If it sits too low, the workpiece can dip into the opening or catch on the back edge. A recessed insert can also affect the consistency of dadoes, grooves, and rabbets.
Fortunately, either problem is easy to correct.
If the Insert Sits Too High
If the insert sits proud of the table, rout a shallow rabbet around the underside where it rests on the saw's support ledge.
Make the rabbet in a couple of passes and check the fit frequently. The goal is to sneak up on a surface that's flush with the saw table.
If the Insert Sits Too Low
If the insert sits below the table surface, install a small set screw near each corner.
The screws become adjustable leveling points. Turn them in or out until the insert sits flush with the surrounding saw table.
Provide Clearance Under the Insert
There's one more issue you may encounter before cutting the final blade slot.
On some table saws, the blade doesn't retract far enough for an uncut insert to sit fully in place.
The solution is to cut a wider relief kerf in the underside of the insert.
This provides the initial clearance needed to install the blank over the lowered blade.
Cut the Zero-Clearance Blade Kerf
Now you're ready for the step that turns the blank into a true zero-clearance insert.
Install the insert and make sure it's properly seated and secured.
Then clamp a sturdy board across the saw table over the insert to hold it firmly in place.
With the blade fully lowered beneath the insert, turn on the saw and slowly raise the blade through the insert.
The blade creates its own perfectly matched opening.
Once the kerf is established, shut off the saw and allow the blade to come to a complete stop before removing the hold-down board.
WOODSMITH TIP: Label Your Inserts. If you make inserts for several blades or dado widths, label the underside of each one. A quick note identifying the blade or setup makes it easy to grab the right insert later.
A Simple Upgrade for Cleaner Table Saw Cuts
After a few coats of finish, your shop-made insert is ready for use.
It's a remarkably simple upgrade, but it can make a noticeable difference. By supporting the workpiece immediately alongside the blade, a zero-clearance insert helps reduce chipout and produce cleaner, smoother table saw cuts.
And because homemade inserts cost very little, there's no reason to stop at one. Make several blanks while you're set up, and you'll have zero-clearance inserts ready for your favorite blades and dado configurations.
Put Your Zero-Clearance Insert to Work
A zero-clearance insert is just one part of getting a furniture-ready crosscut. Learn how the right blade, blade height, workpiece orientation, and feed rate work together to produce smooth, accurate cuts with less splintering.
GET CLEANER TABLE SAW CROSSCUTS → Get Smoother Table Saw Crosscuts
