I have a 
Question for you, or anyone else who knows the answer. 
Dear Jake: I have a Question for you, or anyone else who knows the answer.
Posted By: Dave Murphy
Date: Wednesday, 6 August 2008, at 2:18 p.m.
A few questions for you:
1. On the Invicta photo from yesterday, what is the piece just north-northeast of the bezel insert? Is that the click?
2. Does that piece have any role in holding the crystal?
3. Assuming answer 2 is "no", was it intended by the designer of this watch that the nylon gasket is the only method used here for both fastening and waterproofing the crystal?
4. Assuming that answer 3 was "yes", do you know of a source that supplies crystals and plastic gaskets for use in repairing generic watches of this construction?
You see what I'm getting at here? You (in your role as a watchmaker) could easily source a mineral crystal for 2 or 3 dollars, but how would you hold it in?
I have searched and searched. I find crystals. I don't find the plastic gaskets. But I find glue.
Dave
Messages In This Thread
I have a Question for you, or anyone else who knows the answer. (views: 1)1) That piece is indeed the click, and is what makes the bezel unidirectional. It is not unlike that used on the Seiko 
s
2) It plays no role in the retension of the xtal
3)Yes, the nylon gasket is the only (and ineffective) method used here for both fastening and waterproofing the crystal
4)Yes, I
do know of a source quite close to us in proximity, and although the
gasket used for the Invicta is not a tight fit, and is a very thin and
wussy gasket, once again, this is not unlike the system used on the
modern basic Seiko s ie: the Monster and 007...See what I'M gettin' at, good buddy? 
Where there's a parts supply house, there's 
parts by the millions, and where.... ..you dig?
So the next question becomes:
1. Will you tell me the name of the supply house that you mentioned, that has plastic gaskets mated to crystals?
Yes sir, on my 
case, I notice a black gasket surrounding the crystal. So, it seems that this is a popular way to fasten cases to watches.
So, moving forward, it occurs to me that I have a machine shop here, and I could design a watch case.
I'm looking into different ways of holding the crystal on. But I need to know how to design the counterbore that would hold the crystal and gasket. So far, I'm coming up with two ideas:
1.) Design for a plastic gasket system just like mentioned above. This sounds good to me because of it's simplicity, and effectiveness. If Seiko can use this system and achieve 200m WR, then it sounds good to me.
2.) Another approach is to hold the crystal on mechanically. I recently changed the crystal on my 
,
and I like the idea of holding the crystal against an O-ring. So you
design 2 parts to do 2 different jobs. You get a seal that seals, and a
bezel that retains the crystal. If I recall correctly, this is how the
older Seiko divers work, there is a little retaining ring that is
hidden by the rotating bezel.
One big disadvantage to this method is that a step is needed on the crystal, driving up the price. I'm a cheap bastard, and I would rather buy 3 dollar crystals, rather than thirty.
In the G-S catalog, they depict a deep edge chamfer on the thick glass crystals. Perhaps I could turn a retainer that engages that chamfer. Then press the retainer upon the watch case, which would have the o-ring seal.
The idea of using a mechanical retainer is appealing to me because it seems to me that one could build a very robust case, with more WR than the usual dive watches. Multiple seals could be used.
Ideas?
Thanks,
Dave
..Nelly. Yer gettin' serious here...
} So, moving forward, it occurs
} to me that I have a machine
} shop here, and I could
} design a watch case.
That way lies Madness! 
} I'm looking into different ways of
} holding the crystal on.. So far,
} I'm coming up with two ideas:
}
} 1.) Design for a plastic gasket system..
}
} 2.) Another approach is to hold the
} crystal on mechanically.
Far be it from me to give advice to a Journeyman Machinist.. But take it from someone who's been there. Start simple.
F'rinstance, I spent more time perfecting the screwdown caseback on 2 units of my own 
cases than I did machining all the rest of the 25 piece production run! 
I will say this - it's a worthy project! Go for 2,000 Meter WR! ! 
BTW.. there are ways you could incorporate a flat crystal using O-rings. All it'd require is a screw-on front bezel, similar to my
-Ricky
>>>>I spent more time perfecting the screwdown caseback on 2 units
What problems did you come up against, that you needed to perfect? From your pics, it looks like you helically interpolated about 2 turns of thread. I will be turning these features, rather than milling.
>>>>>screw-on front bezel
Are you sure that Seiko bezel screws on? It might just press on. Anyway, if it screws on, how would you ensure that those 6 "wrench lugs" will properly line up when screwed down tight?
I think if I go this route, I will want to conceal that piece with a rotating bezel.
Oh, and by the way, in your bill of materials, you mention no crystal gasket or retainer. How do you hold them in and seal them?
DAve
>>>} What problems did you come up against,
} that you needed to perfect?
A
fixturing problem. I chose to turn the outside face of the caseback,
then pocket & threadmill the interior on the CNC milling machine. I
went this route mainly 'cause A} it insured I would have the same exact
threadform on both the ID and OD thread and B} the exterior of the
caseback would look more 'finished' if turned. Also milled the wrench
nothches on the lathe.. 
Anyway, this left me very little contact area for the milling fixture to grab. I scrapped 2 pieces 'fore I got my first acceptable caseback. 
} From your pics, it looks like you
} helically interpolated about 2 turns
} of thread.
Spot on!
} I will be turning these features,
} rather than milling.
Your biggest challenge, then, will be getting the thread smack dab all the way to the shoulder. As I'm sure you're aware..
} Are you sure that Seiko bezel screws
} on? It might just press on.
Not 100% sure, no. But it's not like to include ersatz mechanical details for decorative purposes.
} how would you ensure that those 6
} "wrench lugs" will properly line
} up when screwed down tight?
Yeah, could be a problem.. unless you used quite a pliable o-ring, one tolerant of over-torquing.
} I think if I go this route, I will
} want to conceal that piece with a
} rotating bezel.
That could work very, very well. Your case would end up quite massive, I think.. Hmmmmmm. 'Dreadnought' is already taken. I 
for 'Juggernaut'!
} Oh, and by the way, in your bill of
} materials, you mention no crystal
} gasket or retainer.
Correct you are!
} How do you hold them
} in and seal them?
UV-activated watch crystal cement ;
'long as you take a little care in applying the bead, I suspect this stuff is quite water-resistant. K.I.S.S. , right? And, remember, I was paying homage to a watch, not a !
-Ricky
Please 
privately, and I can direct you the right way.
Yes, the second system you describe is exactly what is used for the 6309 ,
and IMO it's a better method which is still used by many companies to
achieve greater water resistance. The retaining ring fits on like a
bezel on some, while on others it's threaded and screws in like a
caseback. In any case, it holds the xtal FIRMLY against an O-ring, and
in the case of the 6309, the ring is in fact shaped like an L so that
the xtal sits in it, and the gasket wraps around the underside of the
xtal edge. As you said, this requires a more difficult and costly
manufacturing process which uses more parts and steps...Doubtlessly,
this is why
abandonned this in favor of the friction method. However, when done
right the friction method can obviously work quite well. I believe that
a 007 has (unlike the 8926 I tested that failed at a measly 6
ATM..sorry 
defender in the thread below) been tested by a fellow WIS to somewhere around 40 ATM.
sir! What do you think of these... double-seal o-rings? They have two little sealing surfaces in the space of a standard o-ring.
I'll bet that they would work well, one for the crystal, another at the back.
...and went northwest instead of northeast.
This that you reference wire is exactly the same bezel retention system as the vostok, and many others.
Just got to Berlin (Germany). Guess now I'll need a beer to get my bearings straight again!
Cheers
Matt
looking for short-lug
watches... (long)
Posted By: Dave Murphy
Date: Wednesday, 11
June 2008, at 3:10 a.m.
Hey, guys.
I have been thinking about a project. It has long been an ambition of mine to attempt to make a watch case.
The more I think about how to dimension a case, the more I realize one fact. I thought I knew what a watch case looks like. The more I investigate, the more I realize that I do not. The aesthetics of case shape are very complex, and when you actually put pencil to paper, some surprises come out. Like how much material is really required.
On to the problem of the day. Here is shown a couple pounds of 316L Stainless that I procured for use in this project. It is 2 inches diameter, or about 50mm, plenty for a watch case, right? Well, not really. In order to get a decently large case size, I need to choose some smaller lugs.
I have traced out a vostok amphibia case to illustrate. This case will just barely fit! It has short lugs, an 18mm lug width, and the case diameter is just under 40mm, not including the crown.
.Get the picture? I have a hunk of stainless, a CNC lathe, and a Bridgeport mill. I will bore and turn all the round features of the case using the lathe, then I will mill away some material at the edges, to form the usual watch-like shape of the lugs and case width.
So, I started a survey of watches that I have, to study the lugs. THe watches with long lugs require lots of material. Take the rolex datejust, for instance. That watch will barely fit within the 2" circle, but the case width is only 36mm.
But for maximizing case width, this Citizen seems to be the champ. The lugs fit within the 2"circle, and yet, the case is 41mm wide. How do they do it? Well, they cheat a bit by milling an angle in the back of the case. This works great, because the strap fits close, and interacts with the case at an angle.
So, I'm looking for a couple more examples of watches whose diagonal lug measurement is 50mm OR LESS.
If you have calipers, I'm looking for other watches that have larger case widths, and short lugs. Or, just eyeball it on a ruler. Could you tell me:
1.)The diagonal distance of the outside of the lugs, but ONLY FOR watches less than 2 inches or 50mm.
2.)The case width of that watch
3.)the lug width of that watch
4.)a pic of the watch.
What was surprising to me was that I had a very hard time finding large watches that can be made within the 2" circle.
Thanks for your help. I started thinking about doing this in order to try to learn something. What I've learned so far is that the amount of metal used in your watch case is more than you think.
And I would like to see some of the other tricks that case designers use to maximise case size within a certain size of raw material.
Dave
Messages In This Thread
looking for short-lug
watches... (long) (views: 137)
>> (views: 23)First, I find it interesting that, even though our main design criteria for the watch case are almost diametrically opposed, we ran into the same problem.
I say diametrically
opposed because you seem to be after an original (albeit somewhat "traditional")
design which is the largest that can physically fit into your raw material
envelope. I, OTOH, was aiming for a specific look - one based on the classic
Marx XI
Navigator.
} ..a
couple pounds of 316L Stainless
} that I procured..is 2 inches diameter,
} or about 50mm, plenty for a watch case,
} right? Well, not really.
I started with 2" diameter material, too...
} In order to get a decently large
} case
size, I need to choose some
} smaller lugs.
Short lugs were not an option for me, as the Mark XI which I sought to emulate has extra-long lugs. My final design measures 55.68mm diagonally across the lugs, even though the basic case diameter is only 36mm. My solution was to saw the bar into 62mm long slugs, then split those slugs lengthwise on the wire EDM machine..
..and flip the workpiece 90
degrees.
I've scaled my CAD model up, and that picture depicts a case with a base circle of 42mm, 62.5mm diagonally across the lugs (and using a 20mm strap). You'll note that it fits easily inside the 2" stock...
This way, of course, the cut
length of the slug, not the diameter, becomes the limiting factor. Furthermore,
by splitting the slugs I was able to get two cases from each.
} ..a CNC
lathe, and a Bridgeport mill.
} I will bore and turn all the round
}
features of the case using the lathe,
} then I will mill away some material
} at the edges, to form the usual watch-
} like shape of the lugs and
case width.
If you orient the workpiece inside the material envelope as I suggest, you'll need a 4-jaw chuck to make this work. Or a CNC milling machine...
} ..they cheat a bit by milling an
} angle in
the back of the case.
A viable alternative, for sure. I've got a couple of watches that sport such a relief angle, and it works very well.
} What was
surprising to me was
} that I had a very hard time
} finding large
watches that
} can be made within the 2" circle.
Get rid of the circle entirely and all your problems are solved.
Here's another view...
Remember, that's a 42mm case. A quick check tells me that you can easily produce a 45mm diameter case using this workpiece & material orientation. Depending on the bezel treatment you could concievably push that to 47mm.
Good luck.. and please keep us posted on your progress!
-Ricky
>>have a wire EDM at my disposal, or a CNC mill. Being a screw-machine shop, Things are very turning oriented here. That's why we have CNC turning but no CNC mill.
I'll look into re-orienting the case within the material, but for now, I think I'm going in the direction of a slightly smaller field watch, or a cushion style case. The four-jaw is out of the question, because I don't even have a three-jaw for the CNC lathes. Again, we are set up for screw-machine work, so workholding will be in 5C collets and step chucks.
By the way, did you ever consider going this route:
On your watch, if you had started out with the 2.25" dia material, you could have turned most of it on the lathe, then cut the lugs using the EDM? Or would the wire leave too rough of a finish?
Dave
I was afraid of that.
But you do have a manual
lathe, right? I'm thinking back to your impromptu "watch winder".
I mean, the turned profile required on a watch case doesn't demand CNC. It'd be nice, sure. But still not too difficult on a manual...
} By the
way, did you ever consider
} going this route:
}
} On your watch, if
you had started
} out with the 2.25" dia material, you
} could have
turned most of it on the
} lathe, then cut the lugs using the EDM?
No. But only because I didn't have any 2-1/4" (or larger) raw
material handy.
} Or would the wire leave
} too rough of a
finish?
A wire EDM leaves a very nice finish. Sort of a smooth matte.. very similar to a beadblasted finish, actually. If I'd had larger diameter material available, cutting the entire planform profile on the wire would've been a pretty good option.
-Ricky
(views:
12) (views:
12)} Don't you just love "Government work"?
Oh aye. I've done some G-jobs that you wouldn't believe.
And I especially love it when your BOSS needs some Gubmint Work...
-Ricky
(views: 6)
(views: 50)
(views: 22)
(views:
6) (views: 9) Sir! (views: 7) 6139 has
similar> (views: 10) That's what I'm
looking for>> (views: 24)>>the case hints at the classic lug shape, but utilizes some space underneath to get enough space to attach the strap.
Any idea on dimensions?
(views: 32)
This is exactly
the kind of data I'm looking for. Thanks! With a >>
(views: 21)lug length of 45mm, it's hard to say whether it would fit diagonally in 50mm.
But I could tone it down a bit so that it fits.
As far as complexity, the chattery wedge cuts just north and south of those crowns add to the complexity.
But the rest is simple enough. The front leading up under the bezel is just a turned taper. The sides are mill cut straight up and down, contouring in only 2 axes. But when you put those two simple toolpaths together, you come up with a 3 dimensional shape that looks visually complex.
This is what fascinates me about case shapes. If you look at all of your watches from a manufacturing point of view, it is interesting to see the choices that designers make.
If I may make a generalization, Rolex cases are quite complex, geometrically. Seiko cases are quite simple from a geometric point of view, and always look more complex than they really are.
Fascinating.I'd be interested to see your project as it progresses, and I'm sure others would. So post a foe pictures if you get the chance. Once upon a time long ago I worked in a couple of machine shops and have used a few machine tools so a project like yours is personally fascinating.
I'm curious about one term. What is a chattery wedge cut.
(views: 24)
(views: 61)
>>because it will max the case size without using much material for the lugs.
Unfortunately, the milling department here consists of a Bridgeport mill that came in the door in 1974. So I will not be able to do much fancy contouring on the sides of the case.
s, it's late here. I'll
catch up in the AM. 
(views: 16)
(views: 22)..but yes, of
course I'll follow up once I'm on the clock.
You know it's a
project near and dear to my heart...
-Ricky
} The bezel
looks too smooth
} to have been milled.
I used a carbide endmill with a 30 degree (included) tip angle, and
the toolpath was simple circular interpolation. A walk in the park.
Mind you, it'd wouldn't be quite so easy on a manual mill...
-Ricky
(views:
9) Ezra! (views: 11)>>first off, 2" is the max size that any of my big screw machines will take. Really, anything over 1-1/16 inch is a challenge for me, for this kind of project. This material is a B1+ch to work with, but somehow, I'll manage.
More importantly, I have a couple of feet of material leftover from a previous project. IIRC, I spent $175.00 on 3 feet of the stuff. It is not cheap! And this is the POOR man's watch forum, after all.
Most guys here just steal their
employer's time by posting during work hours. Well, I steal that bastard's time,
AND MATERIAL!
..you oughta try some 13-8
or 18-8 stainless. Or for sheer
bang-head-against-wall frustration, try some 465C!
Seriously, while I'm most familiar with 17-4 PH stainless, we machine quite a bit of 316, too. It's really no tougher than 17-4.. and cuts like butter in comparison to 465!
The biggest problem with 316 is it's tendency to work-harden, as I'm sure you're aware. Stick with climb-milling toolpaths exclusively and, provided your machine and workholding device can hack it, you'll pretty much avoid that problem.
} IIRC,
I spent $175.00 on 3
} feet of the stuff.
Sounds about right...
} It is not cheap!
Indeed it's not. Not sure what the price is currently, but last fall I was told that a 5" x 6" x 1" rectangular blank of 17-4 PH that we use to make a certain part was running $65.
-Ricky
I steal that bastard's time, AND MATERIAL! (views: 15)
market s,
Dave.. (views: 35)
, and it's a
44mm cushion case.
seems pretty
beefy..
(views: 58)
(views: 16) (views: 14) (views: 13) (views:
14)Hidden lugs is one way to go.
Also from Vostok, they do have a case design with semi-hidden lugs. They beveled the case between the lugs at a 45 degree angle to allow a strap to fit. It actually works well with 1-piece nylon straps because of that 45 degree bevel.
The Vostok 2-o'clock crowns like that really has the same case width as the more typical cases, but lug-end to lug-end distance is reduced a bit.
That's what I'm
talking about>> (views: 26)>>on the 2-crown, from the top, the lug looks short, but from the bottom, there is more room because of the 45 degree cut.
Chris.
