Present type of ground formed gear cutter, invented by J R Brown, pat. 1864

In this type of gear-tooth cutter, which was originally patented in 1864 by J. R. Brown, the teeth are formed and backed off in such a manner that when ground on a line radial to the centre, or in some cases a line forming a tangent to a circle about the centre, the cutter shape is not changed, whilst the backing off permits the cutting edge to be presented to the work with the correct rake and clearance angle.

Because of this method of formation the cutter may be repeatedly resharpened until the cutting teeth are reduced to a thickness too fragile to withstand the cutting pressure, thus ensuring maximum economy in cutter usage. All tooth and profile forming cutters at the present time are made on this system.