Broken screw in automatic poljot movement

[AntonVA]

Hi! I was disassembling a 22 jewels Poljot automatic watch.

I believe the caliber to be the 2415 or in the same family, but there is no engraving.

I was trying to remove the ratchet wheel screw, but it wouldn't go one way or the other. I couldn't find any other way to disassemble the movement without removing it either.

Clearly I should have asked first, but I assumed that the screw wasn't reverse threaded and it was just stuck, so I did some force and it broke.

Doing this revealed that the ratchet wheel has a mechanism I have never seen

I am curious about this system, but especially I want to understand what I did wrong.

The part of the screw that came out is too short for me to see it's threading

Also, the hole where that head fits seems to be deeper than the screw stub, but it may be an illusion.

 

Anyway, I guess I will have to find a new screw and arbor, but having payed 13 euros for the watch I don't know if it makes sense.

Any explanation or advice is appreciated, thanks!

[Shane]

AntonVA,

It looks to be left handed from here and if it wasn't actually stuck and you just turned the wrong way, you might be able to fish it out by poking it with a tooth pick and turning it the correct way.  Just don't use a screwdriver until the last resort.  If you damage the threads, you may never get it out.

That's a very interesting group of parts (I have also never seen them before).  The two three pointed springs look as if they are directional, so they must go in the way they came out or it won't wind properly.  If it doesn't just slip, something may break in the automatic winding gear.

Good luck.

Shane

 

Edited July 23, 2022 by Shane

[Kalanag]

It’s a  Poljot 2415A Rodina   

http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&&2uswk&Poljot_2415A&

The screw has three slots and is therefore reverse threaded.

The mechanism you found is a sliding clutch to decouple the automatic from manual winding.

Edited July 23, 2022 by Kalanag

[AntonVA]

Thank Shane and Kalanag!

I didn't realize it was reverse threaded because in my movement it didn't have 3 slots 

I will certainly try to take the end of the screw out as you say, thank you

[Kalanag]

1 hour ago, AntonVA said:

I didn't realize it was reverse threaded because in my movement it didn't have 3 slots.

So you can not be 100% sure about the thread of your watch. 

[JohnR725]

4 hours ago, Kalanag said:

So you can not be 100% sure about the thread of your watch. 

The three slot thing is a relatively modern thing. Then I definitely agree with the above statement you can never be 100% sure.  if they seem really tight I'll put up penetrating oil on that helps to loosen screws up. But I'm still stuck with a case I almost a flip of a coin because you really can't tell some watches. Usually certain screws are always mostly left-handed and usually the rest of the screws are always right-handed. But never 100% always just because whoever designed watches probably hated watchmakers and that trend continues until today very creative designs that are Not watchmaker friendly

Then your weird three arm spring reminds me of the weird four spring found in the early Rolex automatic watches. They probably do something similar although Rolex has a different type of wheel.

[Kalanag]

1 hour ago, JohnR725 said:

…Then your weird three arm spring reminds me of the weird four spring found in the early Rolex automatic watches…

It reminds me of my Jaeger-LeCoultre 889 

Edited July 23, 2022 by Kalanag

[Shane]

16 hours ago, JohnR725 said:

Usually certain screws are always mostly left-handed and usually the rest of the screws are always right-handed.

From a design point of view, a left handed screw would more than likely be found holding something down that mostly exerted a counterclockwise torque against the underside of the screw head (like a crown wheel).  Right handed screws would be found holding something down that mostly exerted a clockwise torque or no torque at all against the underside of the screw head.  The idea is for these assembly to be self tightening.  Unless there is a good reason for a deviation, companies, if not the industry, these companies function within, would implement what's know as a "standard".   A standard helps speed up the design process, keeping everyone from the designers to the repair personal, on the same page.  They are supposed insure that similar assemblies will assemble similarly.

AntonVA,

I used the word "mostly" in the above paragraph because, within a single design, both CW and CCW forces can be exerted against a screw head at different times. Without the rest of the assembly it would hard to tell what the design intent actually was.

There are plenty of designs that do and do not follow this concept.  So... Like JohnR725 said, "back to flipping coins".

Shane

[Kappa505]

I am working on an old orient that has both the ratchet wheel and crown wheel reverse threaded without the usual screw head markings. 

[anilv]

The device under the ratchet wheel looks like the internals of the reversing wheels in some ETA movements.

Wrt left-handed threads, citizen 0200 movements also use them on both the winding and ratchet wheels. I can understand the rationale for this on the winding wheel but cant see why it would be used on the ratchet wheel as it sits on a suare post (arbor). The only conceivable reason would be to make it impossible to put a wind on the barrel by using the ratchet wheel screw as it would just unscrew.

Anilv

[AntonVA]

Thank you all for the responses.

The only two watch parts that I've broken for now are two left handed screws. The first one in one of my first movements was a crown wheel, I assumed that since there wasn't the triple marking on the head it had to be right handed for sure, right?. Poor me.

And this is the second one. I thought that since the crown wheel had two small screws that meant that a right handed screw was not adecuate, and so if the ratchet wheel had only one screw, it had to be right handed.

Now I know you are all right, you can never bee sure! I should try on both directions alternatively slowly increasing force, and that's what I'll do from now on with stubborn screws.

[Paul80]

I know from my own short experience that I found that 50% of Ladies size watches I have worked on had left hand threaded screws on both crown and ratchet screws with none of them marked as such so knowing if the screw that would not undo was either a tight right hand thread or a left hand thread is quite difficult, especially given how little force is actually need to break a screw head, I tend to assume that all ratchet wheel screw are R/H thread unless they are not and all Crown wheel screws are L/H thread unless they are not .  Difficulty comes when the thread is tight because its seized by rust etc, those will will break regardless of which way you try to turn them.

Luckily with the few I have broken or found broken and the reason the watch was not working, getting the broken bit out was quite easy, either using a screwdriver to simply un screw it, being careful not to damage the threads or by using one of those screw extractor devices, but they only work if the the other end of the screw is accessible (Not a blind hole)