Friday, 31 August 2012

Longines Stem Repair

This is a Longines 9782 gents dress watch belonging to my uncle. The stem appears to have been over torqued, and the the crown has broken off with part of the stem still inside. The problem here is that there is insufficient stem protruding from the crown to remove it easily.

As with many other posts on this blog, you'll have to forgive the poor macro-photography on the part of my camera. Here's the offending crown:

I've decided to chuck the stem, turn down a very small portion of the crown thread. This will expose the broken piece of stem, which I will then be able to extract. Unfortunately, I was unable to chuck the crown successfully as the crown kept wobbling off centre. To remedy this, I'll turn a small carrier which will hold the  crown true, allow it to be turned down. The crown is 2.94mm in diameter, so the carrier is turned down to around 2.93-2.95mm (the measurement differs slightly due to wear on the crown knurling).

A test fit:

Finished carrier:

The crown and carrier chucked ready to be turned down slightly.

Finished crown with my thumb for size comparison. The female part of the crown thread is about 0.8mm shorter than it was originally.

A test fit on the new stem:

Final photos of the movement cased will follow...

My Current Workspace

My lathe tooling has consumed a vast quantity of space (and money), so I've thrown together this super cheap and hopefully temporary watchmaker's bench. I've designated this as my 'clean' space for disassembly/assembly.

Now for the 'dirty' space, my super strong, bomb-proof bench which weights as much as a neutron star:

The big draw contains my milling column, large tap/die set, socket set and my Seiko 6309/7xxx parts boxes:

The middle draws contain the medium-sized lathe tools: milling vise, dog plate, chucks (3-jaw, jacobs), steady rest, a couple of stock off-cuts, and really and many other useful tools.

And finally the small draw, which as you can probably guess, contains small tools/parts: files, bits, centres, mills, centre drills, micro tap/dies, dividers and so forth