Semiautomatic Single Point Threading

Semiautomatic Single Point Threading

Semiautomatic Single Point Threading - The semiautomatic high speed threading lathes are designed to utilize carbide tools. Operating in the range of 300 sf pm and upward, they produce threads of high quality surface finish on all machinable materials including those steels which, because of alloy constituents and/or hardness, do not readily lend themselves to high speed steel tools.

The cutting action is generally analogous to a conventional screw cutting lathe in that the tool is fed into the workpiece (penetration), traversed longitudinally to produce the required thread lead (feed), withdraw from the work at the end of the thread length (recoil), and rapidly traversed to the starting point (return).

This sequence is automatically repeated at successive increments of depth until full thread depth is reached, at which time the machine automatically stops and resets itself to repeat the cycle on the next workpiece. Parts may be held by manual or air chucks, collets, between centers, or by virtually any method applicable in lathes.

The feed and return motions are obtained through a drum type cam or by a reversing lead screw, depending on the make of machine. In the former case, a drum type cam permits rapid cycling by combining the functions of a conventional lathe's lead screw, half nut, and manual return of the carriage.

An additional cam provides the penetration and recoil movements and a third cam system, whose action is superimposed on the penetration and recoil motion, provides the increments of infeed per pass which may be either equal or diminishing in nature.

Spindle speed, number of passes, and infeed increments are quickly determined and set by simple dial adjustments.

The machine design is such that virtually any thread may be cut, right or left hand, straight or taper, internal or external, single or multiple start.

Tooling costs are low compared with thread milling, grinding, and die head threading, since it is only necessary to produce the thread form (V, Acme, Whitworth, API, etc.) on a single point carbide tool bit. With suitable attachments, secondary operations such as turning, boring, and facing may be incorporated. Ease of setup, low initial tooling costs, and inherent speed and accuracy make the application of this threading method practical for both jobbing runs as well as for sustained high production.

Recommended practice is to feed the tool straight into the workpiece, i.e., perpendicular to the workpiece axis, thus providing an even, equal, and sufficient chip load on both sides of the threading tool form.

The chip formation consists of a single chip whose cross section approximates that of the thread form. Tool wear and tool life are commensurate with other single point carbide tool applications.

Operating for a Semiautomatic Single Point Threading Lathe