Truncated cone Brass Bolt & Nut Set small without Washers 7/16 inch (11.1mm)

BLACKBURN

In the late 19th century, Disston and other manufacturers assembled their saws using screws best described as truncated cone screws. These screws, while impressive-looking, quickly fell out of favor as they protruded significantly from the handle. Today, it’s difficult to find replacement parts for these saws. 150 years later, Blackburn Tools offers a slightly more modern version in various sizes. For those making new handles, these screw sets are a simple, clean, and forgiving solution, as the heads do not need to be countersunk and the holes don’t need to be as precise as with other screw sets. No special screwdriver is required. The screw has a square shank behind the thread, which, when driven into the handle, expands the round hole into a square, preventing unwanted rotation.

The thread is an 8-32 UNC (American coarse thread). The screws fit handle thicknesses from 9/16 inch (14.3 mm) to 11/16 inch (27 mm). It’s relatively easy to shorten the screw to the desired length. Instructions below.

Dimensions of the large screws: The nut has a slot 0.050 inch (1.3 mm) wide and 2 mm deep, and no special tool is needed. However, a suitable screwdriver should be used to avoid damaging the head. The maximum diameter of the screw head and the nut is 0.530 inches (13.5 mm), and the head height is 0.205 inches (5.2 mm). The square shank has a side length of approximately 0.160 inches (4.1 mm).

Dimensions of the small screws: The nut has a slot 0.032 inches (0.8 mm) wide and 1.4 mm deep, and no special tool is needed. However, a suitable screwdriver should be used to avoid damaging the head. With this narrow slot, a matching screwdriver might not be readily available. In such cases, the tip of a screwdriver should be ground down slightly narrower. The maximum diameter of the screw head and the nut is 0.430 inches (10.9 mm), and the head height is 0.125 inches (3.2 mm). The square shank has a side length of approximately 3/16 inches (4.8 mm). That’s right, in the small model, the shank is thicker than in the large model!

Installation note: Measure the handle thickness (including any washers or lock washers you may have planned under the screw head and nut) and subtract about 1 mm from the end to determine the cut length of the screw. The screw can then be shortened using a metal saw or a file. The cut edges should be cleaned with the file to allow the nut to turn more easily.