External Thread Cutting on Lathe

External Thread Cutting on Lathe

External Thread Cutting on Lathe - Lathes provided the first method for cutting threads by machine. Although the vast majority of threads now are produced by other methods, lathes still provide the most versatile and fundamentally simple method. Consequently, they are used frequently for cutting threads on special workpieces where the configuration or nonstandard size does not permit them to be machined by less costly methods.

There are two basic requirements for cutting a thread on a lathe. The first is an accurately shaped and mounted tool, because thread cutting is a form cutting operation, and the resulting thread profile is determined by the shape of the tool and its position relative to the workpiece.

The second requirement is that the tool must move longitudinally in a specific relationship to the rotation of the workpiece, because this determines the lead of the thread. This requirement is met through the use of the lead screw and the split nut, which provide positive motion of the carriage assembly.

An external thread can be cut with the work mounted either between centers, or held in a cluck. For internal threads, the work must be held in a chuck. The cutting tool should be checked for shape and be properly aligned relative to the workpiece, using a thread template as indicated.