In the midst of finishing up the four chest frames, I decided to take a detour to the bottom. I started with 3″ wide boards 3/4″ thick, and did a simple shiplap using the dado blade on the tablesaw. However, I didn’t like the overly plain look, even if it was the bottom, and would rarely be seen. What I really wanted was a beaded edge detail to dress things up just a bit. However, I didn’t own a beading bit for the router. What to do?
I had recently seen a Fine Woodworking video of Garrett Hack making and using a scratch stock, and decided to give it a try. My first stop was at the box store for a long thumbscrew and a thread tap and drill bit set to match. Then, I got to work.
I cut a small piece of white oak to a size that was comfortable in the hand. I laid the thumbscrew on top, and marked a line around the block just up from the end of the screw.
I used the tap’s pilot bit to drill a hole into the end of the block stopping after I passed the line. This would allow the tap to cut threads all the way to the slot-to-be. I then took the tap, and carefully cut threads all the way to the end of the hole. This long column of threads gives the screw more support, with less chance of the metal screw stripping out the wooden threads. Marc Spagnuolo has a great video of this process available on The Wood Whisperer’s website.
After tapping the screw hole, a saw kerf provides a slot for the scratch stock blade.
I rounded the edges and corners slightly for comfort, waxed the screw, and ran it into the hole. With that, the blade holder was finished.
To make the blade, I took a small square of old saw blade and dressed the edges smooth and square. Then, using the appropriate size of file, I cut a semicircular profile into the blade, and then smoothed the concave surface with sharpening slip.
Actual sharpening is done by honing the surfaces of the blade to a mirror finish, much like flattening the back of a chisel or plane iron. I’m a diamond hone fan, but any sharpening system will work. Repeating this process will usually restore the blade to cutting shape without having to touch the profile itself.
I mounted the blade in the holder so that the inside curve ends just at the surface of the wood. If you were to move it outwards a bit, you would have a flat step on the outside edge – certainly an option if that is what you want. A twist of the thumbscrew locks it in place. I apologize for the blurry pictures, but it took five tries to get one this good. You get the idea.
To use the stock, simply move it back and forth along the edge of the board being shaped. Often, it will cut better in one direction than another. In the picture above, the cut is being made towards me (away from you). Notice that I’ve got the scratch stock angled slightly – it’s important that the cutting edge trails somewhat until the last gentle pass or two. Think about the way you use a card scraper, and you’ll get the general idea. The rest is a matter of feel and patience – don’t try to cut too fast.
These are the completed bottom boards, and you can see how the beads really dress up the otherwise plain shiplapped edges. When I attach them to the bottom of the blanket chest, I’ll use a couple of finish nails or brads to space them so that the actual gap is the same as the groove beside the beads. Not only will this give a good look, but will allow for expansion and contraction.
The scratch stock is an amazingly simple tool, and cost me all of $1.40 for the thumbscrew. The thread tap and drill bit were about $4.00, and will surely come in handy adding screw threads to other projects. The saw blade was just laying around in the way. While it’s certainly not as fast as a router, it allows you to duplicate existing profiles easily, especially for smaller projects or restorations.
And, it won’t break the bank like a collection of router bits. For the price, it can’t be beat. Give it a try.
Little Good Pieces 