I needed to put a small bead on the edge of a curved skirt for the hunt board I'm building. Because of the curve, my side bead plane wouldn't work, so I decided to make up a little scratch stock for the job. Several people have posted questions about scratch stocks recently, so I took the opportunity to turn yesterday's project into a photo essay for those who haven't used scratch stocks before. As you'll see, they're simple, easy to make and very effective tools.
All you need is a block of wood, a bolt of some sort and a blade. I started with a piece of 8/4 hard maple, a 5/16" machine screw with a knurled head and an old card scraper.
Cut the block to a convenient size and chamfer the edges for comfort. Then drill a hole for the bolt. The bolt engages the cutter and keeps it locked in place, so where you drill the hole depends on the size of your stock and the placement of the cutter.
Then saw a kerf in the block to house the cutter:
Tap the hole for the machine screw:
Next, prepare the cutter. I made mine from an old card scraper, scoring it with a Dremel tool and snapping it off. Clean up the edges with a file and cut the profile. You can cut just about any reasonable profile you need for your work. Mine is a simple quirk and bead - a little over 1/8". I used a 1/8" chainsaw file:
Hone the edges of the profile dead flat and sharp. I took mine through the Arkansas grits up to surgical black. I don't have a stone small enough to hone the inside edges of the bead. I tried wrapping a piece of fine wet-or-dry sandpaper around a screwdriver shank, but it dubbed over the edge and ruined it. I recut the profile and just honed the flats. It worked fine:
I found that my saw kerf was too wide for the cutter. I was afraid I'd get chatter, so I made a shim out of brass shim stock. The non-business end of my cutter extends past the edge of the block so I bent the shim around the edge of the cutter to protect my hand:
Here's the assembled scratch stock:
To use, set the cutter so the profile extends beyond the edge of the block and lock it down with the screw. Reference the cut by keeping the edge of the block in contact with the workpiece and pull or push the stock along the edge. Start with light pressure and adjust the angle of the stock to get a clean cut. A well sharpened cutter will actually give you shavings instead of sawdust. Look closely at the image below and you can see the shavings curling away from the cutter:
Keep repeating until you cut the full profile. Be aware of the grain direction. If the cutter begins to tear out or chatter, change the angle and/or the direction of the cut. After you get the cut started, you can increase the pressure on the stock, but you really don't need to muscle it. Just keep a nice steady pressure and repeat the cut until you get there:
Easy peasy. You'll be surprised at how easy this is and the quality of the cut you can get with a well prepared cutter. Mine required almost no sanding.
Hope you found this useful.