Red tool bit is fixed to an end of blue bar and pink tracer to the other end. Pink tracer moves in groove of yellow cam template. Blue tool bar, two pink bars create a parallelogram mechanism that eases the tool bar motion when the pressure angle in the cam is big (compared to cam sliding follower). Tool bar moves along the axis of rotation of orange workpiece thanks to green slider and orange screw.
Use violet screw of the lower runway to withdraw tool bit from workpiece a little in return stroke.
Attention: profile of the workpiece is a little different from the one of the template because the tool bit has three cutting edges (not a point).