Auto-Scribes

Shop-made center finding

Make these handy, time-saving tools in your shop for a few dollars! Click image to enlarge

By Tom Hintz   

Locating the center of a piece of wood is a common task in woodworking. While finding the center of a wide piece of wood is easily done with a tape measure, centering tape or ruler, the same task on a narrow piece is much more difficult to do accurately. The Auto-Scribes came from my frustration with finding an easy, fast way of handling this task.

   The Auto-Scribes Custom Plan Set provides full-size templates for laying out Auto-Scribes with 6 1/2", 4 1/2", 2 1/2" and 1 1/2" maximum capacities. Material wider than this can be handled with a centering tape measure.

(Top) The key to these scribes is three equidistant points with the tip of a screw at the center. (Bottom) I used a hex-head sheet metal screw to make fine adjustments easy. Click images to enlarge

   The crux of this tools design is accurately positioning three equidistant points, in a straight line. The outer two points are drilled for ¼-inch hardwood dowels, and the center point to accept a small screw through the scribe's body. The full-sized templates included in the Auto-Scribes Plan Set makes this critical step easy and very accurate.

   I built the set of Auto-Scribes pictured here from 1 ½"-wide by ¾"-thick poplar. Virtually any kind of wood can be used but I strongly suggest poplar or a hardwood.

   Before final assembly, I shaped edges on the router table with a 3/8-inch roundover bit. This step is primarily for looks and comfort.

   To use the scribes, choose one that fits easily over your board. Place a dowel on each side of the board, rotate so they are in firm contact with the boards edges and slide it along, letting the screw tip make a fine scratch down the center of the board.

   That's it. Fast, accurate and essentially mistake-proof.
   The only adjustment to the Auto-Scribes is setting the screw for the depth of scratch desired. Remember, you need only be able to see the scratch. It is also important to remember that in some situations we will have to sand the scratch out before finishing.

   I keep the screw tips in my Auto-Scribes adjusted so they make a very light scratch that is easy to see, and just as easy to sand out during preparation for finishing.