Screw Auger: a Steel Blade Twisted Red-Hot, with a Worm, Two Lips and an Eye for the Cross Handle (Holtzapffel, 1846)

"The ordinary screw auger ... is forged as a parallel blade of steel ... it is twisted red-hot."

Draw a steel bar out into a flat, parallel blade, leaving a round end for the shaft. Width, thickness and length are ours: make the blade as wide as the hole you want.

Heat the blade to red, grip one end in the vice and twist the other with a wrench into an even double spiral. Twist in short heats and keep the pitch even.

File the point into a worm (a small tapered screw, as on a gimlet) that pulls the auger into the work. Shape and sharpen the two corners, or lips, to cut at the very ends and a little up the sides.

Forge the top of the shaft into a ring or eye.

He gives no hardening. Ours: harden the cutting end and temper it as for other wood-cutting edge tools, then hone the lips.

Shape a hardwood bar and drive it tightly through the eye as a transverse handle.

From Charles Holtzapffel, **Turning and Mechanical Manipulation**, vol. II (1846), pp. 540, 543 and 545-546 (checked on the archive.org scan turningmechanica02holtuoft). He also describes the single-lip auger: a half-round bar coiled into an open spiral with the flat side outwards, the end shaped like a shell auger. He gives no sizes or heat treatment: those, the tools and the handle wood are ours.