Abstract: An attachment for use with a tool having a cutting surface on one end of a bar consists of a collar that has an opening corresponding substantially to the cross-sectional configuration of the bar and is frictionally supported thereon in any angular or axially-orientation. The collar has a support opening which receives a cutter insert that has its inner end supported on an abutment and is releasably retained within the support opening by a recessed fastener.

Abstract: A machining tool comprising a rotatable holder, a removable, axially adjustable leading element, such as a drill bit, mounted in the holder and a throw-away cutting insert mounted in a fixed, unadjustable position on the holder to fix the position of the cutting edge on the insert axially in relation to the leading element and the holder.

Abstract: A countersinking tool comprising a holder with at least two removable cutting inserts for countersinking relatively large holes. The holder has a locating recess and a seating surface for each insert, and is cut away at various parts to facilitate the countersinking operation. The inserts may be cut away at one part to facilitate the mounting of a plurality of inserts on the holder.

Abstract: A countersinking tool comprises a disposable, flat, chip-like cutting insert mounted on a holder rotatable about its axis. The insert is readily assembled or disassembled on the holder by turning a pin which extends through holes in the insert and the holder. The insert has a flat inside surface for seating on a flat surface on the holder, and the insert has a pair of flat, peripheral side surfaces each of which engages against a respective flat surface or locating portion on the holder to locate the insert in a cutting disposition on the holder. The insert and the holder have various features which cooperate to promote the countersinking function.