Winding stem for calendar watch

I have an old Agon calendar wrist watch from my father that is missing a winding stem.  It looks like the winding stem snapped off at a critical point.  So, I set out to fabricate a replacement.  I've made four replacements thus far, and all but the last ended in failure -- breakage of the part -- but each got a little closer to success.  The replacements #2 and #3 were able to wind the watch, but not set the hands.  Replacement #4 appears to work.

Here's the original; the break is just to the left of center.

From the original, I took careful measurements for plans.  (Beware transcription errors -- I accidentally swapped two digits, which did in replacement attempt #2.)

Here is the original (bottom), the first attempt (top, and the second attempt (middle).

The orange blob on the left of the second attempt is a bit of binding wire.  I thought I had steel binding wire, but it was actually solder-coated copper.  So when I heated it for hardening, the copper melted and welded itself onto the (then already broken) part.

The pictures below chronicle the making of replacement #3.  Before going any further, I'll note that replacement #3 ended up breaking.  It also didn't have the right sized hub behind the flats, so it couldn't set the hands reliably.  I fixed that for replacement #4, but didn't take pictures.

I started by turning a 1/8" steel rod to size: 0.051" diameter, and then trimmed it to size.  After that, I turned the pivot: 0.019" diameter.

Then came the rather delicate task of trying to file the flats.  Since I don't have a filing rest (maybe I should...), I did this by hand with the absolutely finest files I have.  They're not very fine, in the end, but appear to be sufficient to get me started. Below shows a trial fit in the frame.

I finished the filing on an oilstone so that it fit the crown wheel...

Next comes the fairly delicate job of cutting the slot for the portion that grips the handsetting mechanism.  Here it is in progress...

... and here it is finished, with the original next to it.

I had a lot of trouble reaching the graver into the slot to make a smooth slot.  And, as it happens, the hub on the pivot side is too narrow to grip the handsetting mechanism.  So in replacement #4, I cut the slot deeper, with a sharper (more right-angled) slot.

At this point, I parted it off...

And hardened it in water.  (Perhaps should have used oil?)  Here it is bound in steel wire.

Anyhow, this was a lesson learned from replacement #2 -- I left it in its original (not hardened) state for trial fitting and broke it.  And replacement #3 broke after being fully hard... so for replacement #4, I polished and then carefully blued it, so hopefully it can take some stress.

Here's the part at this point...  just before final polishing.  And at least occasionally it can pull the crown wheel back for handsetting.

It's just about the right length, too.

But, I wanted to remove it to inspect the hub, and it jammed and then snapped!  So I had to try again... Replacement #4 seems like it is just about right...

Start-to-finish it took about 3 hours to make replacement #3 and 2 hours to make replacement #4.