<p>What is a "keyseater"? This simple, ingenious - and still widely-used compact machine - is intended to cut both internal and external keyways - either simple, straight-sided ones or, with the correct tooling, a variety of multiple slots of any profile desired, providing that a cutting tool can be ground to the desired shape. The machine consists of a heavy, cast-iron base holding the moor and drive mechanism with, at the top, a flat table with various kinds of T-slots and clamps to secure the work. In the case of the sophisticated Frömag type, at its centre is a tall, hollow guide column inside which runs a reciprocating cutter located at both top and bottom to ensure the most accurate cut. Some other, simpler types of keyseater from different makers, have their cutter exposed, held at the bottom but supported at the top by a simple adjustable thrust bar. With the workpiece located in position by clamps, alignment guides (and sometimes eccentric bushes) and the necessary settings made, the cutting tool, more usually a relatively inexpensive single-point type (not an expensive, difficult-to-sharpen long broach) is pulled downwards on its cutting stroke and lifted free on the upward. The work is cut in stages, each additional depth of cut usually applied automatically and, of course, adjusted in depth as necessary to cope with the particular job.</p> <p>Both mechanical and hydraulic keyseaters are made, the advantage of the latter being that the cutter pulling force can be altered, via valve settings, to suit the size of cutter, dimensions of the slot and the particular material being machined. In addition, with a maximum load set, should the cutter hit a hard spot it will automatically stop and prevent tool breakage. On mechanical machines the tool lift is often by a cam or friction mechanism, the efficiency of the latter liable to be affected by the presence of oil and cutting fluid. On hydraulic models the feed to the cutter and its lift on the return stroke is controlled hydraulically - any lubricant thus having no dilatory effect.</p> <p>With a tilting table fitted, tapered slots can be cut and, when equipped with an indexing plate (typically with 120 division) various multiple slots and splines also generated.</p>