When a customer ordered some new saw bolts for a saw he was restoring, he asked if there was anything that could be done about the medallion. I agreed to take a look at it and see if I could salvage it.
A quick glance confirmed that it would indeed need a new shank. The threads were long gone, and what was left behind was bent. With little to lose, I cut the existing shaft off and started anew.
The shank was turned from 360 brass. The squared portion of the shank was filed by hand, and was made larger than the original so that it would fit in the existing mortise, even if damaged.
The back of the medallion needed some work as well. The first step was to true up the mating surface. To provide more surface area for the solder, and to make it easier to align while soldering, I milled a shallow recess in the back of the medallion.
With the medallion ready, the shank could be finished. After turning the shoulder, I milled the end of the shank with a slight concave profile. This was done so that it would mate with the convex surface left by the end mill at the bottom of the recess.
The actual soldering was the easiest part of the job, taking about fifteen seconds. I used silver bearing solder, which, while not as strong as brazing or silver solder (which has a higher percentage of silver in it), is sufficiently strong for this purpose.
After removing the excess solder and lightly cleaning the surface of the medallion, it is ready to go back on the saw for the next hundred years.