Rotary Broaching, although in use for over 100 years, is a rare sight in the small workshop. And yet, "drilling" square and hexagonal holes in virtually any material has never been so easy! The Compact Rotary Broach can be held in lathe's tailstock or the miller's chuck and will effortlessly transform a pilot hole into an accurately cut hex, square or spline up to a major diameter of 8mm (5/16") and a depth of 7mm (1/4").
Although the process resembles black-magic, it's based on sound geometry. Also known as a "Wobble Broach", the hardened tool sits within the spindle of the broach holder and is free to rotate. The clever bit is that the holder's spindle is set at 1° to the axis of the lathe or mill so that with each rotation of the spindle, a slither is cut by each corner of the broach. With moderate pressure, the broach will progress pretty much as fast as a drill, leaving a crisp sided pattern identical to the head of the broach.
This allows infinite possibilities for the production of custom fasteners, miniature sockets, clock and valve keys, carb jets, tapping collets, double keyways, etc... Female broaches (made with the help of a male broach!) even allow square and hex heads to be accurately generated on shafts without labouriously indexing them under the mill. The Compact Rotary Broach stands out just 45mm and can be held in a Ø10mm collet or an accurate drill chuck.
The kit includes the spindle bearings, radial (2) and thrust, together with all necessary materials to complete the holder and your first 3 broaches. The drawings are detailed in both imperial and metric units and the construction notes show every step. Incidentally, all of the milling required is completed with a perpendicular spindle; and the angles are generated with the aid of feeler gauges.