Jump to content
When you buy through links on our site, we may earn an affiliate commission.
  • Current Donation Goals

Master Watchmaking - gen PAM crown tube fabrication


RWG Technical

Recommended Posts

If you are going to install a genuine crown onto a PAM case, you need a matching tube.

I have seen a number of genuine crown installs where the original tube was retained and simply drilled out larger to fit the gen crown pipe, that is not a good solution, in fact it's a horrible solution.

Why? well simply because the rep tubes typically have an o'ring on them and the o'ring is inserted into a notch cut out of the inner edge of the tube, the notch in the tube for the o'ring damages the o'rings on the gen crown, the damage means that the seal is non existant and the case is allowed to breath with long term damage to the movement. Also, the majority of the rep tubes do not fit correctly against the vertical crown o'ring which provides the seal when the CG lever is closed.

Basically by installing a gen crown in a rep tube, you end up with a case that is open to the atmosphere and that is sucking in dirt and moisture everytime the watch is worn, eventually the watch will be ruined.

The correct way to install a genuine crown is to fabricate a matching tube, a tube that fits the case properly, and more importantly, fits and makes full use of the 3 crown o'rings (2 on the pipe and 1 on the crown) and provides the required seal.

First part of the work is to drill the hole in bar stock, the hole is for the crown to fit into, the drilling is done in stages from small drill to large drill...

1a.jpg

1b.jpg

Next up, I cut the tube down so that it will fit into the case. This is done carefully and the final dimension is to have a slight taper to the finish so that the tube can be press fitted tightly to the case.

1c.jpg

Once that is finished, I have to cut the tube away from the bar stock so I can fit and finish it.

1d.jpg

1e.jpg

The tube is flipped over and re-installed in the lathe. The crown is test fitted, the pipe fits the tube correctly but if you look closely the tube is too large in diameter and doesn't seat properly against the 3rd o'ring in the crown.

1f.jpg

So I reduce the diameter of the outside of the tube until it just fits into the crown, you can see the slight gap between the crown and tube, a perfect fit, a fit that will provide the correct seal once the CG lever is closed.

1g.jpg

Next the tube gets a polish.

1h.jpg

1i.jpg

The tube is ready to be press fitted into the case.

1j.jpg

And a quick look at the inside shows that it's the correct length and fully seated.

1k.jpg

With the crown installed, the crown o'ring is touching the new tube and there is just enough of a gap between the crown and the case to allow the CG lever to press the crown home and flush against the case and seal it all up.

When done correctly not only is the crown supported laterally so you don't get a wobble, the pipe o'rings provide a constant seal, and the crown ring does the final sealing when the CG lever is closed. All in all a professional installation.

1l.jpg

Total time for fabrication of the tube is just under an hour.

Thanks for reading.

Link to comment
Share on other sites

Awesome! Keep them coming :) For me seeing this kind of thing is what this is all about. Also, your time to manufacture is equally as impressive as the result. Wish I could learn to do it ;) Need an apprentice?

As a side question do you think you can make a new pusher stem? I have a piece that needs some help :) Actually never mind I know you can.

Link to comment
Share on other sites

Great mate.... a really useful thread and something I never truly appreciated in terms of the potential damage especially to the movement..

You mention the rep tube has a gasket on the inner edge, typically.... but what about a gen tube?

For example if you have a more recent gen PAM case (say 6 years old) with a tube to recieve the single gasket gen crown (Pre Hex type) then can you mod this to recieve the double gasket crown or does it need a new bespoke fitted tube... to prevent the isues you raise in your post..

Thanks again mate ...

Link to comment
Share on other sites

Thanks for the positive feedback everyone.

@krpster, should not be a problem to make a pusher, as long as I have the old one as a guide or exact dimensions...let me know if you are interested.

@PeteM, the rule of thumb would be, if the gen crown has o'rings on it's stem pipe (like yours does), then you need a smooth bore case tube to allow the o'rings to seat and do the sealing. If the stem pipe is smooth, then you need a tube with an o'ring in it, to provide the seal.

I would love to have an apprentice, it's just too bad we all live so far apart...

Link to comment
Share on other sites

I absolutely love those step-by-step tutorials, even though I lack the skills and the tools necessary to perform anything like this. It's just a thing of beauty how something so neat and clean is developed.

Thanks so much for showing this! :)

Keep up your great work, Zig!

Kind regards

Valerian

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...
Please Sign In or Sign Up