Prototype Diver. 4 Things I don't understand fully.
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  1. #1
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    Prototype Diver. 4 Things I don't understand fully.

    Hi all,

    Let me preface by saying that, yes, I'm building a watch, but it's a learning exercise/labour of love, I have no intention of building an empire... With that in mind, I'll hope that you understand that I'm just an enthusiastic 'noob' with no aspirations of grandeur. I've looked at plenty of drawings, watched plenty of videos and when necessary asked questions to people who know what they're talking about. In this case, I'm just about ready to physically 'make something happen', but there's a couple of details I can't completely get my head around.

    ...I've done my CAD, everything looks good on paper; I'm now about to build a printed resin prototype, to check if my work is going to fit together.

    1/ At some point I'm going to have to talk to a mould maker or CNC engineer about screw threads. I'm not worried about the screw-down crown and case-tube, I'm going to buy those parts in. However, the screw down case back has left me a bit mystified. Let's say the thread is 35mm with a 0.5mm pitch (standard Swiss ISO). Which radius is represented by the 35mm; is it the apex of the thread, the pit or in the middle?
    2/ Securing the crown tube. As this is intended to be a Diver (CIRCA 20ATM) I'm assuming I'll have to do more than simply 'hammer in' the crown tube (as higher pressures will inevitably cause it to move). I've heard of people using solder to secure this part, but to me anyway, it sounds a bit brutal. I've not managed to find any content on drawings or build-logs that really talk about this process. What's the best way to secure the case tube?
    3/ This is the question that's going to expose me (most) as a noob!!! Can someone point me in the direction (of detailed files that show the best method for securing a movement holder to the case... Most drawings just show it 'sat' on an inner lip, but obviously some mechanism needs to be in place to prevent rotation. I've seen indentations on the rings, with (potentially) corresponding screw holes/drilled holes?? in the case, and I'm pretty sure that 'clamps' have a lot to do with this, I've just not found a resource yet, that clearly illustrates how this fits together. In fairness, I'm pretty clueless on the whole 'how to prevent' rotation 'problem', including the movement itself. - I kinda understand how to stop the dial from moving. I have a 'male' extrusion on the underside and a corresponding 'female' on the case (I intend to secure with cement), but this whole science is a little alien to me (fixing the movement in the ring, and the ring in the case), so if there's a video or some reading material out there, that will help me with this, I'd be glad to hear about it.
    4/ OK, last one. When looking at drawings of Diver watches, I consistently notice there's a weird double radii gasket between the bezel and the case (image attached). I'm pretty sure this isn't two gaskets (as they'd be a nightmare to fit), but I could be wrong. Equally, I can't find a part anywhere that resembles this. Any help here would be greatly appreciated.

    Thanks in advance

    Dom

  2. #2
    Member MechaMind's Avatar
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    Re: Prototype Diver. 4 Things I don't understand fully.

    Lets start at the crown tube.
    THe way you fix it or set it depends on your construction. There are different solutions

    Some solder it - this is a solution is often done at cases which are someway done from sheet metal ( e.g. Sterling Silver as you can use the precious metal as a soldering alloy)

    Others just press the tube in the hole in the case … the hole has to be calibrated for the pressfit and the tube is pressed in .. sometimes/ someway sealed with a industrial adhesive against ingress. this - done with a slow curing composite - leaves you some time to adjust the axial position of your treat so the crown is not affecting the thread in winding rest, but when pressed to axial position. ( usually there are used spring loaded crowns for threaded tubes

    Third would be to have a "cap over crown" so Cartier does.

    Regarding the thread … those big thread diameters are usually done on a lathe not with the cutter. The called diametric dimension of a thread is approximately when you use the caliper and measure the diameter of the tread on the screw. ( its not that exact as the peaks of the profile are normally rounded by the forming process but roughly…) … you alternatively could set axial screws and have smaller screw diameter where you can by treading tools for, but dependent on the size the tools are rather sensitive against load changes and break when used in the wrong way

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    Re: Prototype Diver. 4 Things I don't understand fully.

    FWIW, Rolex crown tubes are screwed into a threaded hole ... IIRC, the tap size is M3 x .35mm. The tube has an internal spline that allows it to be tightened; on the couple of occasions I have had to tap a case for one of these tubes, I’ve used a thread locker on the tube threads.

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    Re: Prototype Diver. 4 Things I don't understand fully.

    I don't think he's building a Rolex. But, thank you for the information, it's always nice to know some Rolex oddity.
    Now back to the previously scheduled levity...
    Damn, that's a lot of pieces.
    We don't take $h!+ from a machine (They Might be Giants lyric)

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    Re: Prototype Diver. 4 Things I don't understand fully.

    Quote Originally Posted by ExpiredWatchdog View Post
    I don't think he's building a Rolex. But, thank you for the information, it's always nice to know some Rolex oddity.
    You’re welcome ... and you’ve missed — or ignored — the point. A screwed-in crown tube may be a viable approach for the OP because it permits somewhat less precision in drilling the case than does a press fit.

    It also makes the crown tube a replaceable part. I’ve used generic Rolex-replacement tubes on various divers over the years because it’s pretty simple to pop out a damaged tube, enlarge the hole if necessary, cut some threads, and install a threaded tube.

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    Re: Prototype Diver. 4 Things I don't understand fully.

    Quote Originally Posted by byscott View Post
    You’re welcome ... and you’ve missed — or ignored — the point.
    Sorry for my snarky remark; I see the value in your comment. Did you mean that your replacement tubes are splined on the inside, and what tool do you use to assemble/disassemble them?

    I'm looking forward to R&Ring a tube on a TAG. From what I see, I need to heat the tube to break the adhesive and then press the tube out from the inside, even though there's no direct shot at the reverse side of the tube. People recommend going in at the angle the case allows but I can see mischief ahead. Not looking forward to it.

    Thanks again
    Now back to the previously scheduled levity...
    Damn, that's a lot of pieces.
    We don't take $h!+ from a machine (They Might be Giants lyric)

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    Re: Prototype Diver. 4 Things I don't understand fully.

    Quote Originally Posted by ExpiredWatchdog View Post
    Sorry for my snarky remark; I see the value in your comment. Did you mean that your replacement tubes are splined on the inside, and what tool do you use to assemble/disassemble them?
    No worries ... Iím from New York, where a day without snarky remarks is like a day without sunshine

    Yes, the tube is splined on the inside. The installation tool looks a little like a Torx screwdriver ... as usual the authentic Rolex tool costs an arm and a leg, but there are cheaper generic tools that work well enough. Itís not like they need to handle a stupid amount of torque.


    Quote Originally Posted by ExpiredWatchdog View Post
    I'm looking forward to R&Ring a tube on a TAG. From what I see, I need to heat the tube to break the adhesive and then press the tube out from the inside, even though there's no direct shot at the reverse side of the tube. People recommend going in at the angle the case allows but I can see mischief ahead. Not looking forward to it.
    That sounds difficult. My usual way to remove a damaged tube is to mask up the case to avoid scratches, put the case in a bench vise, and use a small easy-out to pull out the crown tube (from the outside). Fortunately, Iíve never had to press one out from the inside.

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    Re: Prototype Diver. 4 Things I don't understand fully.

    Quote Originally Posted by byscott View Post
    My usual way to remove a damaged tube is to mask up the case to avoid scratches, put the case in a bench vise, and use a small easy-out to pull out the crown tube (from the outside). Fortunately, I’ve never had to press one out from the inside.
    Hey, thanks for the advice, I'll try that first. I hope it's sunny in NY right now.
    Now back to the previously scheduled levity...
    Damn, that's a lot of pieces.
    We don't take $h!+ from a machine (They Might be Giants lyric)

  10. #9
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    Re: Prototype Diver. 4 Things I don't understand fully.

    Here's everything you need to know about cutting threads; someone was nice enough to post the relevant pages from Machinery's Handbook http://www.nashua.edu/paradisem1/Mac...Thread_09A.pdf. The threads O.D. is measured at the tips of the thread and is nominally the same as the shank diameter for shanked bolts. The actual sizing of the spiral groove is tested with a thread micrometer; it looks like a normal mic except the spindle is pointed at a 60deg. angle and the anvil has a V groove between two ridges, also at 60deg. (google thread mic). It measures the pitch diameter and when cutting threads single point, you keep cutting until the pitch diameter falls in the specified range.

    Internal threads are harder, they do make thread micrometers but they are more elaborate and need a standard ring to calibrate them. Usually, a machinist uses an Go/NoGo gauge, which is plug with threads at each end; at the minimum and maximum diameters. These are also very expensive. In a home shop setting, the external thread is cut using a mic to verify, then use it as a go gauge and cut until you just get a good fit. All is done single point on a lathe.

    I did notice a section on thread milling, I can see in today's precision three axis CNCs, it would be possible to program a tool path to match a thread spiral. Tool clearance might be a problem though.
    Now back to the previously scheduled levity...
    Damn, that's a lot of pieces.
    We don't take $h!+ from a machine (They Might be Giants lyric)

  11. #10
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    Re: Prototype Diver. 4 Things I don't understand fully.

    Quote Originally Posted by byscott View Post
    My usual way to remove a damaged tube is to mask up the case to avoid scratches, put the case in a bench vise, and use a small easy-out to pull out the crown tube (from the outside). Fortunately, Iíve never had to press one out from the inside.
    For dive watches, this is the normal way to remove either a threaded tube or a press fitted tube - easy out with some heat usually. Some of these have nearly "blind" holes in the case so in these instances, you can't press the tube out from the inside.

    For watches that are much less water resistant, the tube can usually be pressed out from inside rather easily.

    Cheers, Al

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