Saturday, May 10, 2008

Making a chessboard pt 3

Now I need to cut the board across the strips. The problem is, I don't have a good edge to push against the tablesaw fence. The solution is the panel jig. In the simplest case this is nothing more than a straight piece of wood that serves as a fence attached to a sheet of plywood. Now, the panel jig's fence is perpendicular to the board's direction of travel through the table saw. The board has 2 good edges for that. Here's the panel jig. As you see, there's isn't much to it.

(note - I built mine upside down and reversed. That is, most of these jigs have the fence on the side closest to the operator. And usually the jig is on the left of the blade, not the right. I don't know why I made it this way now. But it has advantages and disadvantages... )

The next two pictures show the before and after of me cleaning the edge of the first square. Note the board's good edge is against the fence. That's how I know this edge will be perpendicular.


and after...

As soon as the edge is clean, I immediately write the numbers 1 through 8 on the board, on the first maple strip, such that when the new strips are cut each has a number. This will allow me to reassemble the board in the same order. It keeps the grain matching and looking good.

Now a challenging task is ahead - I need to make 8 strips - but but how wide? The problem is that the squares aren't exactly 2 1/4" like I had planned. They are about 2 3/16". I measured across the board and found it was 17 7/16" wide. I divided by 8 to get the average width of a square. This was something bizarre, of course, something like 2 23/128ths. I could approximate it to 32nds of course... Instead, I converted the fraction to decimal... 17.96.. and set my dial caliper. Now that I know how wide these strips should be, how am I going to do it? I should be able to cut these on the table saw now that I made a good edge. But that will leave a thin piece of wood stuck between the fence and the blade. In addition to being dangerous, I don't have any wood to spare if it gets chewed up.

I decide to use the panel jig instead of the tablesaw fence. I use my calipers to measure from the leftmost edge of one of the saw blade's left-set teeth to position a wooden stop:

Note the bar clamp - the stop must absolutely not move. Now I push a clean edge against the panel jig's fence, and push a clean edge against the stop. The sets the width of the strip to be cut as accurately as I know how.

There's now nothing left to do but push wood through the saw. I make sure the chessboard doesn't slip by pushing the board against the jig's fence, but I push the jig through the saw. Better jigs have a toggle clamp that pins the work to the jig. If I used mine more often I'd add one.

So I make a few cuts, measuring each one with the calipers to make sure nothing has slipped. Here I've cut 2 with the next ready. You can just see masking tape on the trailing maple edge - I has some trouble with this splitting out as the blade passed through. The tape adds enough support to prevent this.

Ok, all 8 strips are cut and laid out in order on the panel jig.

Now what? How do you get a chessboard out of that? Simple! Rotate every other strip end-for-end!

Suddenly the game board appears!

The next steps will include a light sanding of the new edges to remove any wood splinters or burrs that could prevent a good glue-up. Then back in the clamps it goes for gluing! After the cleanup I'll glue the whole board down to a sheet of plywood to strengthen it.

I'll add a border to it to protect the outside squares and hide the plywood substrate. I consider the miters at the border's corners to be the most difficult part of the project.

Then the real finish sanding will happen. This will level the board and the border and hopefully be silky smooth. Finally, I'll apply a finish. Oil gives luster and depth, polyurethane makes it tough as nails. Maybe I'll do both. I have not decided.

More to come...

1 comment:

  1. Use a fresh Diablo 10 In. x 80 Tooth Ultra Finishing Saw Blade...