How I make Wooden Screws
Some tools and methods
A freshly cut wooden screw of Hard Maple.
This screw was cut in steps to demonstrate how threads are cut in multiple passes. Eleven passes through the die would be needed to fully thread a screw like this one. It is 1-5/8″ in diameter with a pitch of 3 threads per inch. (3 tpi)
Screw cutting Dies for external threads
Here a screw is being threaded in my die set-up. To use, an unthreaded blank is fastened to the master screw using a short length of radiator hose and clamps. It is then driven through the die by hand power, using the bit brace visible at far right. The master screw feeds the screw at the correct pitch through a specially built die that matches the diameter and pitch of the screw. Before each pass the die cutter is advanced by about 1/80th of an inch and thinned raw linseed oil is brushed on to soften and lubricate the wood fibers so they can be cleanly cut. An unthreaded screw blank is visible in the foreground.
Another view of the die. The screw blank has been fully threaded and is ready to remove for final shaping on the lathe.
Taps for cutting internal threads
This is a tap which which is used to scrape a helical thread inside a hole bored through the side of a press. The threaded jaw of a press is clamped to the front (at the left here) with the steel shaft of the tap passing through a hole of the same diameter. The cutter is advanced incrementally and many passes are needed to fully thread the hole. This tool is powered by hand using a bit brace which engages the bolt head on the end of the shaft. This is slow but has the advantage of allowing the fit of the screw and jaw to be made ‘just right’. The cutter scrapes rather than slices through the wood and is used ‘dry’ with no linseed oil lubricant.The white plastic tool is a gauge for adjusting the cutter. A close view of cutter and tightening method below. Switching out the master screw and tap shaft allow for this tap to be used for different sizes and pitches.
A 5 tpi bottoming Tap
This is the bottoming tap and shaft connector. To use this tap a 5 thread per inch (5 tpi) master screw would be attached at the other end of the shaft connector and the assembly installed in the tapping frame (along with a master ‘nut’). The tapping frame for this tap is different than the one pictured above.
The tap won’t reach ALL the way to the bottom of a blind hole, but comes very close.
A cutter for the tap made from HSS drill rod.