1. Wood ZCI Building Steps
2. Finish for Wood ZCI
The nice thing about making a zero clearance insert out of wood is that you can use a thickness planer to mill the wood down to the exact thickness required. For my table saw, the distance between the table saw tabletop and the four tabs (which the bottom side of the ZCI rests on) is 18/32”. No such animal (regarding wood thickness) is available at your local big-box store that I am aware of. Therefore, I need to mill the wood to be used for making the ZCI down to 18/32” thickness.
A shot of the table saw tabletop and three of the four tabs referenced above are shown below (Photo 1).
For wood, I used maple, and the board I used was 3/4” x 7” x 37”. That will easily give me enough material for two ZCIs. Try to use quartersawn wood with the grain lines running as shown in Sketch 1 below or at least as close to quartersawn as possible (in order to avoid warpage issues).
1. Wood ZCI Building Steps
Step 1—Using your thickness planer, reduce the thickness of your wood (quartersawn) down to the thickness required for your ZCI. For my table saw the required thickness for the ZCI is 18/32”. (The maple board I started with was 3/4” x 7” x 37”.)
Step 2—Now rip your board to obtain a board width approximately 3/4” wider than the width of your ZCI throat opening thru the table saw tabletop. Since the throat opening width on my table saw is 3-25/32”, I ripped my board down to a 4-1/2” width.
Step 3—Next, I cut the board I’m working with down to a length that is at least 3/4” longer than the length of the ZCI throat opening. Since my board is 37” long, I just cut it in half, so I ended up with two boards approximately 18-1/2” in length. My ZCI throat opening is 13-3/8” in length, so my 18-1/2” board length is way more than sufficient.
Step 4—Penciling the outline of the new wood ZCI (trace an outline for the thumb hole at this time also) is next on our agenda. Use your existing ZCI to trace the outline for your new wood ZCI as shown in Photos 2 & 3.
Step 5—To cut the outline out of your ZCI use a band saw (or jig saw) and stay proud of your penciled outline by approximately 1/16”. And then use your combination
belt/disc sander sand as required to tweak your ZCI to fit snugly inside your table saw throat opening.
Step 6—To find the center point for a 3/4” diameter thumb hole–I used a circle template, 6” metal rule, and awl. These are shown below in Photo 4.
Use a 3/4” diameter Forstner bit to drill the thumb hole. I drilled from the top side of the ZCI but I didn’t drill all the way thru the ZCI. When I got close to the bottom side of the ZCI, I stopped and used the awl (shown in Photo 4) to puncture thru the bottom side. Next, I drilled thru the ZCI from the bottom side. Drilling from the top and bottom side of ZCI kept any blow out from taking place on the drilled thumb hole.
Step 7—For cutting the blade slot on your blank ZCI, you need to remove your
10”-diameter table saw blade and install an 8”-diameter dado blade. If you try to install the ZCI blank with your 10” diameter blade installed, the 10” blade will not allow the ZCI blank bottom side to rest against the four tabs below the tabletop throat opening. However, the use of an 8” diameter dado blade will allow the ZCI blank to rest flat against the four tabs below the tabletop throat opening.
With the 8” diameter dado blade installed, raise the blade all the way up. Next, use a triangle as shown below (Photo 5) to measure say about a 1/4” proud of the 8” dado blade, and pencil this location on the table saw rip fence. (The two penciled lines are labeled on Photo 5.)
Now lower the 8” diameter dado blade down all the way and install the blank ZCI. To hold the ZCI blank in place while raising the powered up 8” dado blade thru the ZCI blank, position two magnetic featherboards as shown in Photo 6.
Note that the two magnetic featherboards are positioned such that they don’t cross the two red lines shown in Photo 6. The two red lines represent the edge of the orange triangle shown in Photo 5, as it is placed on both sides of the blade slot which will be cut. Bottom line, don’t cross the red lines regarding placement of the magnetic featherboards, and your magnetic featherboards will not get cut when you raise the 8” dado blade up thru your blank ZCI.
With the two magnetic featherboards properly positioned and locked in place, raise the 8” diameter dado blade up thru the blank ZCI to cut the blade slot.
Step 8—Remove the 8” diameter dado blade and install your 10” diameter table saw blade. Raise the 10” blade all the way up. Next, use a triangle as shown below (Photo 7) to measure say about a 1/4” proud of the 10” blade, and pencil this location on the table saw rip fence. (The two penciled lines are labeled on Photo 7.)
Now lower the 10” diameter table saw blade down all the way and install the ZCI (that had the 8” dado blade raised up thru it in Step 7). To hold the ZCI in place while raising the powered-up 10” table saw blade thru the ZCI, position the two magnetic featherboards as shown in Photo 8.
Note the placement of the two magnetic featherboards along with how they are positioned relative to the pencil lines (labeled in Photo 8). The red lines across the tabletop are drawn perpendicular to the table saw rip fence. The area between the two red lines indicates the area where you want to ensure that your magnetic featherboards steer clear of: to keep your magnetic featherboards from being cut by your 10” table saw blade when fully raised.
With the two magnetic featherboards properly positioned and locked in place, raise the 10” diameter table saw blade up thru the ZCI to complete the cutting of the blade slot.
Step 9—Next, clamp your existing ZCI to your new ZCI. With pencil, transfer the location of the existing ZCI hold-down pin to new ZCI. The existing hold-down pin is shown in Photo 9 below.
After transferring the location of the hold-down pin from the existing ZCI to your new ZCI, drill a 3/32” dia. hole (3/4” deep) and with hammer tap in an 8d finishing nail, as shown in Photo 10.
I used the “squaring-up jig” shown in Photo 10 to square the 3/32” drill bit with the ZCI surface being drilled. The jig consists of two scrap pieces of 1x material brad nailed together as shown.
Next order of business is to cut the 8d finishing nail length to match the length of the hold-down pin on your existing ZCI. To matchup with my existing ZCI hold-down pin length, I used 5/32” for the new hold-down pin length. I used a Dremel rotary tool and cutoff disc to cut the 8d nail to length, and then I used a fine file to remove the burrs left by the cutoff wheel.
2. Finish for Wood ZCI
For finishing, I applied one coat of polyurethane (poly). I used one part poly to one part mineral spirits.
I used a brush to apply the poly. And after the poly dried, I then went over the ZCI with 0000 steel wool, and called it a day.
Photo 11 below shows the completed ZCI after the poly finish was applied.
Making a ZCI is a relatively easy process. The build process shown above consists of nine steps and application of a finish.
The following power tools were used for this build:
(1) thickness planer
(2) band saw (or use a jig saw)
(3) belt/disc sander
(4) table saw
(5) drill press
(6) battery-powered drill
(7) Dremel rotary tool
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