I know some have had issues with the PRS 20 crown threads being stripped. I certainly have (ref: viewtopic.php?f=17&t=53614).
My purpose here is not to be critical of the watch (I love it and wear it everyday...now), but I just wanted to relate my experience in getting this issue sorted. Some may find it useful if they are having similar problems etc.
As discussed in that thread I had Fricker repair the threads. I'm guessing they just replaced the crown tube, screwed it back together and promptly sent it back to me. I thought that would have been that.
Unfortunately, the crown again stripped the threads in the tube about 3-4 weeks after being returned to me.
Sending the watch back to Fricker again was not really an option for me as i suspect they would merely replace the crown tube again and not investigate why it was being stripped - perhaps they would assume the problem was "pilot error". I may be wrong, but I just didn't want to risk further expense, freighting the thing halfway around the globe again, and the potential language difficulties (although my contact there had excellent english, I understand she has now moved on).
I resolved to get some advice from a local watchmaker to see if there was a fix he could manage.
He played-aroung with it for a while and said "yep, its certainly stripped" (thanks!). He suspected that there was something "not quite right about the alignment" of the movement. This made me think about why some watches seem to be threaded and others have no problem.
Perhaps there is an issue in the casing of the movements of some watches. They are not being placed exactly right thereby the crown would not be engaging with the tube exactly perpendicular to the tube; resulting in inevitable threading.
Anyway, I wasn't really concerned about the screw-down crown functionality to the watch; certainly not if it was going to cause ongoing grief. So I asked him if he could convert it to a normal crown operation.
He said it was a relatively simple process and completely reversible. So I went ahead with the changes.
He has remade the crown tube by grinding down the threads to a smooth surface. Then he has re-made the crown stem so it operates simply as a normal crown. This cost me AUD250 and I think it's fantastic. He pressure tested it to 6 bar saying he was reluctant to go any further due to the crystal backing; no problems.
Now I can wind it, wear it, and not worry about it.
Crown tube stripped back:
Crown "closed" against case, nice and snug:
Happy cat (not much help whilst studying):
Any comments? Perhaps this should be in mods and wreckers.
Good solution! My 20 went back to Fricker for a repair, but I have to admit it made me nervous about the crown so I don't wear it as much as I'd like to. I don't really need it to screw down, especially if it's good to 6atm without. Worth thinking about indeed.
Dave E
Skating away on the thin ice of a new day
My watchmaker told me that the water resistance doesn't come from the screw-down crown function, but from the seals etc in the crown. The screw down crown is really meant just to protect the crown from being knocked about and possibly affecting the seal (eg, if you are diving etc).
He thought the modified crown could actually handle a pressure test to the 10 bar that the watch is meant to be rated to, but he thought the case back might not, so he didn't want to risk it; he replaced the case back seal too.
What is interesting is that when I received the watch back from Fricker, they had done a pressure test to 5 bar only (they provided the print-out). I'm not sure what that means.
Interesting....the screw down crown always put me off the PRS20, especially with it being hand wound....something that I don't think goes together well. A good conversion though and something I would do if I went for a 20.
Having owned a few 30 - 40 year old Rolex Precision hand-wind with screw down crown, I had no qualms about putting a screw down crown on the PRS-20. I've wondered why some people have had problems with the crown whilst most people didn't and thought perhaps the large crown allows you to develop a lot of torque and isn't very forgiving if you mis-locate the crown on the tube. Just a thought.
It won't have a screw down crown when it's made again.
Eddie
Whole chunks of my life come under the heading "it seemed like a good idea at the time".
Some people think tighter is better. As if the water sealing properties are in the screw threads.
What most folks don't know is that for most thread of the size and pitch of crown tubes require about 1 to 1.5 inch-ounces of torque to be as locked in place as they need to be in order not to move. The average strength man can with a good well knurled 6.5 mm crown, apply about three times that.
The crown on my PRS-20 LE is the most precise and easily threaded screw-down crown I have used, by some margin.
Pete
Good idea. There is always a percentage that will strip the threads. I've seen people treating screwed-crowns as if they doing-up wheel-nuts.Originally Posted by swanbourne
Also, if possible have the 'tubes' in the lugs put in as standard.
john
Costume jewellery. Ouch!!!
Another point made to me regarding the movement alignment etc was that the issue is exacerbated by the size of the watch; ie, the bigger the watch diameter the more difficult it is/more important it is, to be precise with the alignment. This makes logical sense as the further out the crown sits, the greater the margin of any, even miniscule, mis-alignment = the greater the chance of stripping.
...I still think it's a magic watch :D
Godd fix and good post, my PRS-53, handwind, is happy to shower, swim and generally deal with life, can not see why the 20 would be any different and certainly support Eddie in the decision to remake the 20 without screw down crown. Now if only I liked that style :(
We chatted about this a few months ago. A great idea.
Eterna's new diver is 1000 meters proof with a non screw down crown. For the past five years people have been very doughtful of the Fortis 200m divers with non screw down crowns and not one report of one failing. Funny enough most watches sold these days are rated to a depth but only tested to 3-5 ATM. Divers mostly 5-10 ATM no matter how proof they claim to be. Some of the high end of course claim to test every specimen to the claimed depth.
When Mühle Glashütte developed their SAR watch, they claimed that the crown would withstand 2000 metres and actually tested the watch to 2000 metres in the ocean. When the watch was retrieved, it was still waterproof although the case was distorted and the movement crushed. Kind of puts all the extreme depth claims in perspective.
Eddie
Whole chunks of my life come under the heading "it seemed like a good idea at the time".
:shock: :shock: :shock:
Put things into perspective.
At the same time I have dived to 25 meters with my PRS-53 with no problems at all.
In salt water, the pressure at 2000 metres is 2859.366 psi or 197.1463 bar.
Eddie
Whole chunks of my life come under the heading "it seemed like a good idea at the time".
Indeed, though most people take their watches, (yes, even dive watches), off before even going in the shower.
:shock: :shock: :shock:
Put things into perspective.
At the same time I have dived to 25 meters with my PRS-53 with no problems at all.
Best Regards - Peter
I'd hate to be with you when you're on your own.
Is it a manual or an auto PRS-53?
john
Costume jewellery. Ouch!!!
In the case of my LE, the crown works perfectly--as I've commented before--but the pressure pushing the crown outward is very noticeable; as I screw the crown back in, if I were to simply turn it it might strip the system. With a little pressure inward, as I turn the crown, it is absolutely a solid system that feels to me will last a lifetime or two. my 2c.
Its the manual. My old neighbour has a tester and he tests all my watches to the 6 ATM limit of his machine. Otherwise I would have not taken the risk.Is it a manual or an auto PRS-53?
john
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