Long-Pilot High-Speed Wood Bits: A Flat Plate and a Long Square-Edged Pilot, No Screw Feed (Smith, 1951)

"It is extremely important however that these edges 15 and 16 be of exactly constant width from top to bottom, else the holes will not be bored true, and chattering and heating might develop."

Cut three 170 mm lengths of 10 mm octagonal tool steel. Heat 50 mm of one end to a bright orange in the forge and flatten it on the anvil to about 3 mm thick, centred on the bar. Hammer across it with the peen to spread it wider than the bit, about 2 mm over its size: 15, 21 and 27 mm. Draw the neck down smoothly where the blade meets the bar and keep the blade in line with it. Reheat as soon as the colour fades to red. Finally heat each one to a cherry red and let it cool slowly in the air, to soften it for filing.

Glue each outline on its blade, centred on the bar, and grind to the lines on the bench grinder, dipping the steel in water often. Grind the faces flat and parallel to 2.4 mm (3/32 inch). Grind the plate's two side edges and the pilot's two side edges square to the faces and exactly parallel; check the plate's width with the caliper at the top and the bottom, it must not change. Grind three flats on the end of the stem, 20 mm long, for the chuck's jaws.

The bit turns clockwise seen from the stem. Grind each cutting edge either side of the pilot square to the axis, with no top rake, and a clearance of 15 degrees behind it, on the face that trails. Grind the pilot's two point edges to 58 degrees included and give each a clearance of 9 degrees the same way. Leave a 1 mm flat at the tip, square to the axis.

Heat the blade and the neck evenly to a cherry red, until a magnet no longer sticks to it, and quench it straight down in water, moving it up and down. Rub the faces bright with a stone. Heat the shank gently 30 mm behind the blade and watch the colours run down; quench again as soon as a dark straw colour reaches the shoulders and the point. Do the other two.

Hone the cutting edges on the shoulders and the point with the stone, keeping their angles, and take the burr off. Chuck a bit by its flats and bore a scrap of hardwood: it should start on the point without wandering, cut two clean shavings from the shoulders and leave a round hole of its own size; check it with the caliper.

**Eston H. Smith** of Indianapolis, assignor to Benjamin B. Aufderheide, US 2,543,206, dated 27 February 1951, filed 23 July 1948. He claimed a flat plate on a stem with a flat pilot, their edge faces at ninety degrees to their faces, a pilot point of 55 to 60 degrees with 8 to 10 degree clearances, and cutting edges square to the pilot with a clearance of between 15 and 20 degrees (his text says 10 to 20). His figures are for the 3/4 inch bit; the 1/2 and 1 inch bits are ours, with his pilot and edge height. His stem is about 1/4 inch with flats; ours is octagonal tool steel with three ground flats. He gives no material or heat treatment; those are ours.