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What is a Tool Post?

Paul Scott
Paul Scott

A tool post is the part on a lathe that holds the cutting tool securely during machining operations. The post then bolts onto the compound rest via a conventional hex or Allen head bolt or a quick release locking mechanism. There are many different designs of this device which cater to various cutting bits and machining operations. A tool post may accommodate a single cutting tool or have locking facilities for several different tools. Most are static, although rotary posts are available for cutting spherical shapes.

The tool post on a lathe is the part of the machine which holds the tool tip during cutting. It generally consists of a tool steel base or column featuring a single or multiple slots or holes to accommodate tool tip shanks. These tool slots are shaped to accept a specific profile of shank and may be square, dovetailed, or round. The tool bit is held securely in place in the tool post slot by two or more locking bolts.

Man with a drill
Man with a drill

In the case of slots intended for square shank bits, tool slots are usually cut into the side faces of the tool post. These slots are often of a dovetail profile to ensure a secure fit. Holes intended for round shank bits are generally drilled through the body of the post. The locking bolts for square shank tools pass through the upper edge of the slot. Those for round shanks are passed through the top or side of the post body.

Some tool post designs feature several dovetail protrusions which accept similarly slotted, removable tool clamps. The use of multiple tool clamps allows for a comprehensive range of tool bits to be used without having to remove the post. Tool bit clamps are held securely on the post dovetail by means of a bolt or a wedge. The clamps feature appropriate tool bit slots and locking bolts to secure the tool bit.

Tool posts are typically bolted onto the lathe's compound rest with a conventional bolt or a quick release mechanism. Generally the post is held static while the compound rest, cross slide, and saddle allow for axial, perpendicular, or diagonal tool movement. The tool bit may also be moved forward or backward in the post to allow for fine adjustment. Rotary tool posts used to cut spherical shapes pivot on a center pin and move the tool tip around in an arc to cut a round profile. Those which accommodate several tool bits often only require release and turning to present a different tool tip during machining.

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      Man with a drill