Copy Machining on the Lathe

What is copy machining?

Copy machining is a method of duplicating a physical profile or shape using a lathe equipped with a mechanical or electronic copying attachment. In this process, the toolpath of the cutting tool is guided by a template or master, enabling the lathe to replicate complex contours and geometries that would be difficult or time-consuming to program manually, especially on manual or semi-automatic lathes.

What is copying lathe?

Copy lathes (also known as duplicator lathes, or copy turning) are most commonly found as wood lathes, and are used to repeatably produce the same part over and over. This is often useful on projects like bannister railings where many identical parts are required. Copy turning is more suited for wood turning because the need for precision is low, and shapes can be more easily copied with simple wood turning chisels, than in metal lathes where often different cutters are needed to copy different shapes due to the higher demands of cutting metal. Copy machining in metal lathes has largely been superseded by CNC machines, which can reliably repeat the same cuts but have fewer limitations and less need for an operator to be involved.

Can you copy machine on a metal lathe?

Copy machining on metal lathes is still possible, as seen in this video from Bizzi Bee Workshop, using a spring loaded slide fitted with a bearing as a stylus to follow a template, and using an indexable carbide profiling tool for cutting:

In traditional mechanical copy lathes, a stylus or tracer physically follows the surface of a pattern (often a hardened steel template or an existing workpiece). The motion of this stylus is mechanically linked—via levers or hydraulics—to the cutting tool, which moves in concert with the stylus across the workpiece. This allows operators to replicate ornamental shapes, curves, or tapers with precision and consistency, commonly used for furniture spindles, gunstocks, or custom automotive parts.

In more modern implementations, electronic copy systems use linear scales, servo motors, or CNC retrofits to achieve similar outcomes with higher repeatability and less operator input. However, the fundamental idea remains: rather than programming or manually controlling the toolpath for each individual feature, copy machining leverages an existing shape as a guide.

While CNC machining has largely superseded mechanical copy lathes for most industrial applications, copy machining still finds use in low-volume production, repair work, and artisanal manufacturing where creating a digital model may not be cost-effective.