When it’s okay to screw up your wood

When it’s okay to screw up your wood

Anybody who collects antiques knows of the myriad of applications that old world woodworkers found for threaded dowels (see “Best Applications” on page 69). The large, coarse threads offer remarkable holding power and an astonishing degree of torque. And now, with the Wood Threading Kit—which offers precision cutters—you can make short work of cutting both inside and outside threads, though a few precautions are in order.

THE KIT: The kit includes a threadbox for threading the dowel and a tap to thread holes for the threaded dowel. The hard maple threadbox has a cast and machined aluminum guide and a V-shaped steel cutter held in place by a brass cutter lock. The matching tap comes with a steel T-bar handle that provides torque while threading the pilot hole.

THreading SETUP: For external threading, choose perfectly round and straight-grained hardwood dowels for best results. I took the threadbox to the lumberyard to check that the dowels I bought were a good fit—not too loose or tight. Use the hole in the rectangular hardwood block screwed to the bottom of the threadbox as a guide. The dowel should fit into this hole without any slop.

Following the instructions, I sanded a 1/8" chamfer on the dowel end to be threaded by rotating it against a belt sander at about 45° as shown in Photo A. Then I clamped the dowel vertically in a bench vise with wooden jaws, and applied a light coating of linseed oil as a lubricant during threading. (The oil can be reduced later on with mineral spirits, if a different finish will be applied, and tung oil works, too. See the Tip Alert.) More lubricant usually means a smoother cut, but a bigger mess.

THE TEST: Next, I placed the threadbox on the dowel end, applied a little downward pressure during the first turn, and then kept turning in a clockwise direction as shown in the above photo. Once you start, do not back up more than a quarter turn or you could mess up your threads. If the cutter is sharp (and ours came from the factory that way), the whole operation will go very smoothly. I achieved excellent results on the very first try.

THE Tapping SETUP: To make matching internal threads, I found that the tap is even easier to use. First drill an appropriately sized hole (1/8" smaller in diameter than the dowel) in the workpiece as shown in Photo B. If drilling a through hole, back the workpiece with scrap to avoid tear-out on the bottom face.

THE TEST: Now, secure the workpiece in a wood vise or elsewhere, slip the T-handle in the tap, and turn the tap clockwise into the hole as shown in Photo C. It’s important that the tap is vertical to begin with. Unlike the threadbox, reverse the cutting motion constantly to clear chips. A little oil goes a long way here. Bottoming taps, sold separately, are available for cutting threads all the way down to the bottom of a blind hole.

BEST APPLICATIONS: The Wood Threading Kit proves ideal for making antique planes, handscrews, bar clamps, vises, and veneer presses. In the world of home furnishings, you’ll see threaded parts used in adjustable candle and music stands, novelty boxes (having wooden nuts and bolts), tabletop nutcrackers, knockdown furniture, and toys.

TESTER’S TAKE: Though the kit is remarkably easy to use, the cutter will require sharpening with extensive use. I found it fun to use contrasting species such as walnut dowels on maple projects. Two things to keep in mind when threading dowels are to oil the threads before screwing the dowel into the hole (or it will never come out!), and also to thread a long dowel and then cut it off close to the threadbox, so that you don’t have to reverse the cutter along the part that you want to keep.