GMF DJ41 frankening

[KJ2020]

I use GS Hypo for some things too. I used a couple blobs on the dial of that DJ41 I recently put together. The dial feet go into holes drilled in the movement holder and are not anchored. There was so little clearance between the dial and the hour hand I was worried that the slightest dial lifting could cause contact and scratch it.

GS Hypo is also a commonly used glue on crystals that don't have gaskets so yeah that would be a less extreme attempt to gain WP. It is crazy messy with the stringers - I hate using it for that reason. Plus it dries too fast to allow much adjustment. I used to use it on DWOs but no more. Strictly 30 min slow cure epoxy now.

This bezel will be getting epoxied onto a case. It's a combo mod build with parts from different models. The original bezel construction didn't allow for a normal fit or rotation on the new case but I don't see that as necessary since it's decorative anyway. I had to remove a lot of material on the bezel underside.

In case you were wondering, rep GMTs with gem bezels don't have an all blue one. Subs that do have all blue use a 2824 so you can't do a movement swap easily. The lengths we go to for a certain look, geez.

 

[WatchSmith.US]

KJ2020 Yes it's a beautiful build as you always do and I'm just as impressed with the amount of metal you removed, how you removed it, and that you lapped the underside of the bezel so nice and flat. Damn that's good.

Agreed on the stringy, fast drying GS Hypo. I hate the stuff and it's a last resort. I don't know how anyone could do much work with it. I guess the only reason I used it is because it's an old watchmaker's glue.

 

[McPwn]

I was thinking of using a thin film of silicone sealant(the ones u use for fixtures in the bathroom) around the edges of the gasket to kind of 'fill in' any gaps. Or could use a tiny bit of loctite blue. However, hard to say for sure if its leaking from the case side or the crystal side. The water is pooling by the edges of the crystal when running cold tap water on top of it, so its either come in from under the bezel, which is my guess.

I just want it to be waterproof enough for every day use, like if you're washing hands, etc. Don't need 10 ATM's or anything.

 

[KJ2020]

I tried to use silicone caulk to adhere an insert to a bezel early in my rep adventure. Wow what a mistake! It's really hard to apply the tiny quantity you would need to exactly the spots its needed. I made a huge mess and worse I let it cure so it was fun digging it all out. Um hmm.

A thin bead around the base of the crystal gasket might work, it's not a bad idea. It would have to then be smoothed down flat to a really low profile to not interfere with the bezel. Or just press the bezel right away. It would take much longer to cure that way but will eventually.

I use syringes in modding for various purposes. Maybe see if caulk is loose enough to flow into and then out of one? Of a tiny hole in a tiny tube of hand squeeze caulk?

 

[McPwn]

Think I figured out the problem. The GMF crystal is about 32.75mm in dia. The Gen 25-318 crystal is 32.60mm in dia. So the rehaut/case outer diameter is slightly too large for the gen crystal, and when installing a gen-like crystal gasket, it stretches the gasket slightly when pressing it all the way down, causing a slight gap to appear between the crystal and gasket lip. So it would seem like my options would require sanding the case rehaut outer wall down some, so the gasket doesn't stretch as much.

Or maybe I don't have quite the right crystal...

 

[KJ2020]

Think I figured out the problem. The GMF crystal is about 32.75mm in dia. The Gen 25-318 crystal is 32.60mm in dia. So the rehaut/case outer diameter is slightly too large for the gen crystal, and when installing a gen-like crystal gasket, it stretches the gasket slightly when pressing it all the way down, causing a slight gap to appear between the crystal and gasket lip. So it would seem like my options would require sanding the case rehaut outer wall down some, so the gasket doesn't stretch as much.

Or maybe I don't have quite the right crystal...

Interesting you mention that. On the TT BP DJ41 I posted above, the replacement crystal was slightly bigger than the damaged one I replaced. That's why I had to sand the inside of the bezel some. So I wonder if there is a difference in crystal size between the 116 and 126.

A gen crystal gets it's part number in part by the diameter of the lower step, where the gasket hugs the side. So maybe your lower step is 31.8mm?

The other two measurements you mentioned look very much like what I encountered. I took about 0.08mm off the bezel, all the way around.

 

[McPwn]

Interesting you mention that. On the TT BP DJ41 I posted above, the replacement crystal was slightly bigger than the damaged one I replaced. That's why I had to sand the inside of the bezel some. So I wonder if there is a difference in crystal size between the 116 and 126.

A gen crystal gets it's part number in part by the diameter of the lower step, where the gasket hugs the side. So maybe your lower step is 31.8mm?

The other two measurements you mentioned look very much like what I encountered. I took about 0.08mm off the bezel, all the way around.

That info was really helpful. So as we now know, and which they admitted when announcing V2, the GMF V1 case had a 32.0mm crystal aperture / crystal inner diameter, whereas gen is 31.8 (25-318 part no.). This is what caused the problem.

I ended up sanding/filing down the crystal aperture wall to make the OD closer to 31.8mm to match the gen crystal, but .2mm is quite a bit to do, especially on a circumferential surface - hard to do it evenly given its a circle. I ended up using a diamond file to get it down to 31.88-31.85 or so, and the crystal now will stay in place and not rotate around freely within the gasket due to the extra .2mm slack. It's not going to be 100% waterproof, but it'll do for now.

I also replaced the caseback with one from an ebay DJ41 case, and that shaved another 0.2mm or so off the thickness. So that plus the lower gasket height on my shaved gasket brought it down to 11.7-11.8mm thickness (gen).