is a contributing editor to AW. He teaches furniture making at the University of Rio Grande, Ohio.
These Hard-Working Traditional Clamps Are Easy and Inexpensive to Make by Mike Dunbar
When I started working wood professionally more than two decades ago, I bought many of my tools secondhand, including a number of wooden hand-screw clamps (commonly called handscrews). I soon grew to appreciate the usefulness of these simple tools. (See photo, above.) Unlike commercially available, steel-thread handscrews» wooden ones can't be adjusted to a wide range of angles. But all-wood handscrews are much less prone to slippage, thanks to wood's resilience. When you tighten the rear screw, it bows slightly, creating a spring effect. If the clamped workpiece shifts slightly, the bow compensates to maintain pressure.
Today, antique wooden handscrews are coveted by woodworkers and tool collectors, and they cost more than I'm willing to pay. But with a little wood and a tap-and-dic set, you can duplicate these classic clamps in your own shop.
Matched tap-and-die sets come in several sizes for cutting threads in different diameters. I got mine from Conovcr
Woodcraft (Box 418, 7785 Mentor Ave., Mentor, OH 44060, 800-433-5221). The tap cuts threads in a prcdrilled hole. The die, or threadbox> cuts threads in wooden rods or dowels. The two tools will cost you around $60, but the set pays for itself if you make several clamps.
An all-wood handscrew consists of only four parts: two jaws and two screws. (Sec drawing, opposite.) Make the jaws of a diffuse-porous wood such as maple, birch, or cherry. For the screws, use a strong, rcsilcnt, ring-porous wood such as hickory, ash, or oak.
I find that handscrews with 11 -in.-long jaws and l6-in.-Iong screws are suitable for most jobs, but you can make these clamps in different sizes to suit your needs. The throat depth should be about half of the jaw's length. To determine the screw length, add to your desired opening capacity one handle's length plus the total thickness of both jaws. Refer to the chart on the facing page to match screw diameter and spacing with jaw size.
Wood holding wood. These shop-made clamps have no steel jaws to mar the work; they can be used for a variety of clamping assignments.
1 like to make handscrews in batches rather than one at a time. Cut your turning blanks for the screws from straight-grained stock. The handle diameter determines the thickness of your turning blanks. (See chart).
Note that the front and rear screw blanks, or rods, are turned differently. On the rear rod, the end opposite the handle has a smaller diameter than the screw thread. This nipple fits in a blind hole in the upper jaw. On the front rod, the handle should have a square shoulder where it meets the jaw. (Sec drawing.)
Turn your screw rods accurately: Too small a diameter and the screw will slop around in the jaw; too big, and the die simply won't fit on it. Before you begin threading the rods, coat each one liberally with a 50/50 mixture of boiled linseed oil and mineral spirits. This lubrication makes for easier cutting action and also prevents excessive wear on the die's cutting edge.
Clamp the rod in a vise, set the die on the rod and turn it clockwise while pushing down. When you feel the tool
Threading the rod. Once the thread is startedDunbar removes the screw handle from the vise and completes the thread by turning the die.
Tapping the jaw. Holding the tap verticalDunbar starts the thread with firm downward pressure.
start to track easily, you can remove the rod from the vise to complete the threading. (See top photo, above.)
Cut the jaws from straight-grained stock and lay out the hole centers on each jaw. Both holes in the lower jaw require threading. To determine the "root" diameter for these holes, refer to the directions provided with your tap.
After drilling the holes, brush some oil into each hole to be threaded. Dip the tap into the oil and insert the tap's pilot, or unthreaded lead, into the hole. Holding the tap vertically, turn it clockwise with a firm downward pressure to start the thread. (See bottom photo, left.) After a few turns, the tap will bccomc cloggcd with chips. Back it out.
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