Saving a screwdown crown

[jdm]

Someone had tried on a large Sector watch at the jeweler shop. Only later the owner found that the person managed (how?!?) to snap the stem in the little time he handled it, but didn't say anything. The crown is signed and of a peculiar look, of course Sector service center said that it's not available anymore. 
Then, somehow I botched on the correct way of removing a stem broken flush on the crown, that is to cut around the top of the female threaded section about 1mm to grab it. The sliding portion left for good and the fixed one was ruined. Time to think something different, all in all it took about two years until yesterday.

All work was done an a non-watchmakers baby lathe with standard tools. An extremely useful one is the carburetor jets gauges below.  These are now discontinued or sell for a stupid price but I had secured the pair from a German metrology seller. As the usual I apologize for the rough pictures.

 

I started by drilling a blind hole in the original crown "core" to be the largest possible without touching the threads.

 

Then cut off the button from a spare screwdown crown.

 

That revealed the mistery of how the pipe, which holds the sliding portion and its spring, is attached to a screwdown crown. It's screwed in as well!

 

But, once turned to press fit size into the hole of the original crown (3mm) there was not enough material to hold a firm friction fit. That I remedied turning and pressing in a brass sleeve. I left the contact surface a little rough to improve friction on the 0.05mm interference. I don't know why but most of my mechanical repairs involve sleeving and shimming.

 

Then I turned a tube to push the above into the crown. It's sized so to be also used as a stump on the staking set.

 

It went in without issue. Compressing air in there is not ideal, but once I realized it was too late to pull it out back and cut an escape groove.

 

The finished item works fine on the case, all is left to do is to cut a new stem to size and return it to the happy jeweler.

[watchweasol]

Nice one jdm  some fine work hope the jeweler appreciates the job.