Although table saws are relatively safe for most work when used correctly, they can still be improved in terms of safety and performance with the use of additional equipment.
One such piece of equipment is the zero-clearance insert.
This insert is currently being used on table saws around the world.
It is relatively simple, safe, and increases the performance of the table saw while adding an extra layer of safety.
In this article we will cover:
- What is a Zero Clearance Table Saw Insert?
- How Do You Make a DIY Zero Clearance Table Saw Insert?
- Can you use a Riving Knife with a Zero-Clearance Table Saw Insert?
What is a Zero Clearance Table Saw Insert?
The zero-clearance insert is designed to replace the throat plate included with most table saws.
The throat plate is normally removed when you use a stacked dado blade.
Such blades are used to cut dadoes or rabbets and are too wide to allow the throat plate to stay in place.
It is not safe to use a table saw with the throat plate removed, which is why the zero-clearance insert has been created.
It can be placed in the slot left open by the removal of the throat plate.
In fact, the zero-clearance insert is pretty much like a standard throat plate in terms of its size, shape, and thickness.
The difference is that the throat plate does not have a pre-cut slot.
You can either purchase or create an insert that is wood or plastic.
Once the insert is installed when you put in a dado blade, you just turn on the saw and increase the height of the blade.
When raised, the blade will cut through the plate and not leave a gap on either side, hence the zero-clearance.
Why Use Table Saw Insert Plate (The Pros)
For most other types of blades, the throat plate is perfectly suitable.
It is designed to allow for clearance of different types of blades that operate at angles other than 90-degrees.
The zero-clearance blade is used with a specific blade or kerf in mind.
When used with the dado blade, it removes the gaps on either side which allows the sawdust or loose material to fall through.
Plus, the insert provides additional support that decreases the chance of chipping when making crosscuts.
Limitations of Using Zero-Clearance Inserts (The Cons)
The most obvious limitation is that the insert will only allow a specific type of blade to be used, namely the one that it is designed for by you or purchased from a store.
When you change blades, you will need to add in a new insert that allows it to just pass through.
Many shops will have different sizes of zero-clearance inserts to fit the different blades that they own.
Another limitation is that the insert will wear out at some point.
This is because the opening for the saw blade will widen over time which will require the insert to be replaced.
Add to that the insert is only being used for one purpose, such as one designed for a specific angle.
For example, if you are making 45-degree cuts in the wood, then only an insert designed for blades that sit at a 45-degree angle can be used.
How Do You Make a DIY Zero Clearance Table Saw Insert?
You can purchase a prefabricated insert from different sources, but you can make one on your own using existing materials.
Step 1- Choose the Materials
You will need a good piece of wood to create the insert.
You can go with several materials, but plywood is the most suitable because does not expand or shrink with the seasonal weather changes.
Birch plywood is an excellent choice because it is quite hard and durable.
You can also glue two hardboard sheets and attach a laminate on both sides to create a blank.
Laminate or phenolic sheets are also well-suited to creating inserts.
But whatever you choose, the thickness must be slightly less than the throat insert of your table saw.
This means using material that is ¼” to ½” in thickness.
The blanks you create should be of that width, but an extra inch or so in length along with being somewhat wider to properly fit within the dimensions of where the throat plate was located.
Step 2- Select Tools
You will need the following set of tools to create the insert from the material that you have selected.
- Table Saw
- Sander or Sanding Block
- Drill and Driver plus Spade Bits
- Combination Square or Calipers
- Eye & Ear Protection
- Pencil or Marking Knife
Step 3- Create Layout
Remove the throat plate from the table saw.
Now use the combination square or calipers to get the exact dimensions of the throat plate.
You will use these measurements to create your insert.
This means the width, thickness, and length will be recorded.
Next, place the throat plate over the blank or material that you have on hand and trace its outline with a pencil.
This will provide you with the outline needed to cut your insert.
Step 4- Cut to Width
Now, use the table saw to cut the width of the blank.
You can reduce the number of cuts by using one edge of the blank as one side of your insert.
Be sure the fence is properly adjusted so the cut matches the opening left behind when you removed the throat plate.
Step 5- Cut to Length
You can use a miter gauge to hold the blank in a perpendicular setting.
This will allow you to cut the blank to the proper length.
You’ll want to cut just outside the outline that you made, so you can sand the final material down to the exact size.
The miter gauge should be set to a zero-degree angle to ensure a proper cut.
Step 6- Make a Miter Cut
Create a 45-degree cut with the miter gauge by removing two of the corners from the blank.
This will leave behind a small portion of the wood that you can sand away later. You can reposition the blade to cut off the remaining corners.
Step 7- Sand
Now that the blank has the right shape, sand down the excess material until it meets the line that you traced.
You can use a sanding station or a belt-sander that is fixed in an upside-down position to do the job.
Use fine-grit sandpaper as that will work nicely. From 150 to 220 should work quite well.
You can always sand any remaining material away by hand with fine-grit sandpaper after using the station or belt sander.
Step 8- Test
Now, place the insert in the hole left by the removal of the throat plate. It should fit snugly.
If not, hand sand away any material that is keeping it from sitting properly in the hole.
Remember, do not over-sand the material or it will not work properly.
Step 9- Clamp & Cut
Now that the insert is ready, all you need is the hole for the blade.
You can do that by securing the insert in place by covering it with scrap lumber such as a 2 x 4.
Clamp the lumber down so that it does not move and keeps the insert tightly in the hole.
Now, start the blade and slowly raise it through the insert and the lumber.
Once the blade is fully raised into position, lower it and then turn off the blade.
Remove the clamps and lumber and you should have a perfectly cut insert.
Step 10- Create Finger Hole and Test
Once you locate the place for the finger hole, use a spade bit and drill it out.
Most finger holes are ¾”. Once drilled, you can smooth it out using sandpaper.
Once the finger hole is set, put in the insert and test it out with the blade by making cuts of different sizes to ensure that it works properly.
Can you use a Riving Knife with a Zero-Clearance Table Saw Insert?
While creating an insert for the blade is simple enough, making one for a riving knife does take a little more effort.
However, the principle is still the same.
You start by using the table saw insert, as supplied.
Raise the blade about an inch and fit the insert you created for the blade on top and make sure it is aligned with the factory insert.
Next, move the rip fence against the edge of the insert and lock it down.
Remove the zero-clearance insert from the blade, turn on the saw, and then place the insert next to the rip fence to add length to the slot.
This should make the two cuts align correctly.
Next, guide the insert along the rip fence until you reach the opening.
Now, turn off the saw and let the blade stop spinning before removing it from the cut.
Gluing a kerf-wide spacer into the end of the slot will ensure that the slot will not close up around the blade.
Just be sure there is still good clearance for the riving knife, and you are set to go.
A zero-clearance insert will improve the performance of your table saw by taking away the otherwise nasty edges to certain types of cuts.
It will also reduce the number of kickbacks or jams that might otherwise occur.
Hi, I am Mark Garner a professional carpenter, woodworker, and DIY painter. I live in the small city of Peoria, Arizona as a semi-retired woodworker. I have started this blog with a simple motive to help you with my wood experience in this sector. If you like to know more about what I love doing and how it all got started, you can check more about me here.