I recently needed a jig to trace lathe turnings. I tried a variety of designs but none produced the accuracy or ease of operation that I wanted.
While rummaging around my shop, I discovered an extra set of 10-in. ball bearing drawer slides (see Sources, below) left over from another project. I attached a single slide to a bracket and attached a pencil to the slide with a notched wood block and Wing Nut. The bracket fits in a dado in the jig’s base. The lathe turning is held between a couple of sharpened machine screws. The right holder is attached to a T-track with a T-bolt and knob so I can move it for different part lengths. To use the jig I move the slide in and out against the turning while I slide the bracket left or right. The pencil does the drawing and I end up with a very accurate tracing of the part.