[su_box title=”Kerf (noun)” style=”soft” box_color=”00cccc” title_color=”#00cccc”] 1 : a slit or notch made by a saw or cutting torch. or 2 : the width of the cut made by a saw or cutting torch[/su_box]
Kerf cutting (or kerf bending or kerfing) is a technique that allows you to laugh in the face of mother nature. Let me explain. If you’ve looked at a forest, or any plant, you’ll notice that there aren’t a whole heck of a lot of straight lines and angles. On top of that, dry lumber doesn’t like to be bent. In order to get the rounded rectangle feeling that we are going for on the dash, we can manipulate the wood to do things that it normally wouldn’t do by bending wood or kerfing.
I built a very rudimentary jig for my table saw to kerf my boards evenly. (here’s a link to my better kerfing jig) Essentially, you just need to use 2 nails that have the same shank thickness as the kerf of your saw blade driven at the proper offset to accomplish even kerfing.
Once you have your jig built you need to determine the size of your panels (or whatever you’re building) and cut the front and back of the boxes. Now that you’ve got 2 even pieces you can measure around the outside of them and that will be the length of your kerfed piece. Simply cut through your workpiece leaving no more than 1/8 of the wood left. This gives the wood enough play to be pliable but leaves it stable. Depending on how long your non-curved areas are you may not have to kerf the entire board, bending wood only over a radius, as was the case with the larger panel. I do caution you though to be generous with the amount of kerfing you do.
MORE KERF CUTS = MORE PLIABLE RESULTING BOARD
Once your workpiece is kerfed you need to get ready for some bending wood. If you happen to have a steam box for bending wood, then, by all means, use it. More than likely, you don’t. So, my suggestion is you take the kerfed piece into your bathtub and pour a stock pot’s worth of scalding water over the piece. As you do this the wood will absorb the water and become pliable. This will allow bending wood around your shaped pieces extremely easy.
Take the prepped piece back and form it around your front and back pieces, then simply clamp away. Use lots of clamps, weights, friends, whatever you have handy to hold it together while the piece dries and locks into the shape you’ve forced it into. The amount of time it will take to fully cure will vary based on your workshop temperature, humidity, and mood of the wood that day. Once you’ve got your friends bending wood (and I promise, they’ll love you for it) you can then determine your method of attachment. After it has had time to cure you’ll end up with a nice bent piece of wood that conforms to the front and back.
I went with standard carpenter’s wood glue and no brads. Once the glue is laid on all the connecting points, it’s right back to clamping and bungees until the piece is fully dry and cured. After it has had time to cure you’ll end up with a nice bent piece of wood that conforms to the front and back. With some simple sanding and some fine tuning on the edges you’ll be ready to go for the application of your finish of choice.
For more details on kerfing wood for bending you can check out this article from Old House Online all about the topic