6309 7040 case restoration - WordPress.com...Seiko 6309 7040 Case Restoration (missing stem/crown...
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Seiko 6309 7040 Case Restoration (missing stem/crown tube) R.K. Newton
10‐16‐13
I lucked upon a craigslist listing for an original owner 6309 7040 in good condition
for $130.00. Concurrent with the purchase I ran across this 7040 on ebay. It came up
as a buy it now for $100.00 with the listing noting the absence of the crown tube,
and suggesting the watch was all original with the exception of the crystal and bezel
insert.
Pictures from the listing
Pictures I took of the case after disassembling the watch (The threads were bad enough I could not screw on
a crown)
As I am a tinkerer and collector with an attraction to Seikos, and with a complete
watch in hand, I dove into the ebay purchase with the idea of putting together a
decent wearable watch. In retrospect, my only error in judgment was in thinking the
project would be simpler than it turned out to be.
The first order of business was to make a plan for the replacement of the
stem/crown tube. I began with a search of the web for any information on similar
projects, with no luck. I was able to find discussions regarding the issue of a
damaged stem/crown tube with most contributors suggesting that a case in this
condition should be considered a throwaway. There was some discussion about the
fairly sizeable investment in watchmaker services to rebuild the missing/damaged
tube. The negativity pushed me a little harder to make a usable watch.
Using the complete watch as a guide I took measurements. Through a couple of trial
and error purchases of taps and dyes, I was able to determine the thread pitch of
the crown and tube. It is metric, 3.5 x .35. I work for a company that has machine
tools and I have access to the machine shop after hours. We also have a lot of scrap
material in bins. I was able to scrounge up a piece of non‐magnetic, ¼” stainless
steel rod. I turned a part as close to the specs I could determine from the complete
watch, with the correct size hole for the stem. I turned the threads on the part
giving me two and a half turns of the crown to lock. I left the end of the tube to be
inserted into the case oversized so I could turn it down to match the hole in the case
once I removed what was left of the old tube.
This the new tube after the insert portion has already been turned to fit the case
I then tackled the case. As I started to create a jig for pressing out the old tube, I
realized how badly buggered the tube was inside the case. I felt like the old tube
needed to be drilled out as opposed to pressed out. I set up the mill with a drill bit in
the chuck that matched the bore of the old tube and used the drill bit to align the
case in the vise. I held the case with some wood bits so as not to mar it with the
jaws. I then drilled out the old tube stepping up in drill bit size until I had a clean
hole in which to insert the new tube.
Next I needed to make a jig to hold the tube so I could turn the case insert end down
to fit the hole in the case and to use to press the new tube into the case. I used a
piece of half inch aluminum rod. I drilled a hole to match the O.D. of the tube which
inserts into the crown, then drilled a shallow hole the correct diameter for the 3.5 x
.35 tap to match the threads on the new tube. The jig allowed me to screw the new
part into the jig and hold the jig in the chuck of the lathe.
Jig to hold the new tube New tube in the jig
I turned the new tube down and milled a portion of the tube away. The tube is
milled in this manner to accommodate the movement inside the case. I then pressed
the tube into the case.
Case drilled out and prepped to receive new tube
New tube inserted into the case
I had decided to purchase a used donor movement, new dial and hands so I could
keep the original movement, dial and hands intact. I purchased a new stem and
crown as they were not part of the ebay purchase. I spent some time cleaning up
the case and assemble the whole thing with the new components. Still need to
replace the bezel insert.