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Lemania 1873

Brian3

By Brian3
in Your Walkthroughs and Techniques

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Brian3 Watch Enthusiast

Brian3

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One of my favorite chronographs to work on is the Lemania, here is one I overhauled at home two weeks ago for a friend, the hammer had been 'over adjusted' by a watchmaker in the past resulting in not resetting the heart cams correctly, I enjoy micro mechanics and made a replacement with oversized hammers and contact surfaces to allow proper adjustment to be made. The pic on the rodico is it close to completion, spent a little more time on the finish to allow it to 'blend in' as it was a display back, other pic is the completed movement. Time consuming but was a nice rewarding job to work on.

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Brian3 Watch Enthusiast

Brian3

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7 hours ago, matabog said:

tell us more, pls!

what steel did you use? how did you hardened it? how did you do it, actually? :)

 

7 hours ago, szbalogh said:

Wow that is a superb job! Cant even tell that it is replaced just by looking on it. Nice beveled and matching finish! To what color did You temper it after hardening? How thick is it? What tool did You use for cutting?

Thanks!

First thing is to have good quality steel, higher carbon content the better, without this you will not be able to harden it.

I started with 0.8mm sheet, glued the original hammer onto it and cut it out using a jewelers saw frame, (leaving the hammer ends and contact surfaces slightly larger to allow me to adjust it later in the watch),  once the shape has been made I fit it to the watch and check all contact points and adjust accordingly.

For the hardening heat the piece until orange and quench it between two heavy steel plates, one of which is flooded with oil, this method eliminates the possibility of the workpiece warping, at this point the metal should be glass hard so I temper it a touch, took it to a deep straw color then allowed it to cool.

Spent a lot of time on the finishing, I made a hand tool for black polishing that holds workpieces perfectly flat allowing me to apply a similar finish, I used fine aluminum oxide powder on a glass plate mixed with a little oil, lots of trial and error here and experimenting with different pressures etc, once complete I beveled the edges using a hand held burnisher.

Hope you can follow my rambling, it's really not too difficult to do, just several processes to follow with lots of checking on the movement to double and triple check sizes.

Brian

 

 

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szbalogh Super WRT Addict

szbalogh

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Recently i was watching a vodeo on Youtube, the watcjmaker guy made a flat part something like this. He just heated the piece with a gas torch and let it drop in water. Hardening is still a mystery for me. What is You opinion, what is better? Fast cooling in water vs. slow oil cooling between steel plates? 

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matabog Super WRT Addict

matabog

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Someone told me that cooling in oil is better because it has a higher boiling point. In water, it will start to boil and not all the work-piece surface will receive the same cooling - in this way not only you will not do a good job hardening the piece, but you actually might brake it.

I never done it myself, but I intend to...

B

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Marc Distinguished Member

Marc

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Whether you use water or oil to quench the piece depends on a lot of different factors, including the mass and shape (the heavier the item the more heat it can hold, long thin things warp more easily) of the piece to be quenched, and the way in which it is to be introduced into the quenching medium. In an ideal world the piece will be cooled at the same (rapid) rate simultaneously over its entire bulk, so as to avoid variations in hardness, and warping.

Every now and again I indulge in the practice of knife making from stock such as old files, suspension leaf springs etc; material that needs to be annealed to work, and then hardened and tempered for use. The quenching medium of choice is always oil and this is predominantly to avoid warping.

The problems with water are it's comparatively low boiling point, and the fact that steam is a relatively good insulator. I use a deep steel jug with a relatively small open surface as my quenching vessel which means that the blade has to be introduced vertically into the oil. If I were to use water then the tip of the blade would enter cold water which would instantly boil creating an insulating layer of steam around the rest of the blade, preventing it from cooling as quickly as it should. This leads to different cooling rates along the length of the blade, which in turn runs the risk of warping, and uneven crystal structure within the blade resulting in weakness. Because of its higher boiling point, with oil you don't get the insulating layer around the work piece, so in turn you get much more rapid, even and consistent cooling throughout the length of the blade. (you also get a pleasing little flame playing across the surface of the oil (pleasing that is if you a bit of a Twisted Fire Starter like me!!))

A shallower vessel with a greater open surface would allow the blade to be introduced horizontally which would probably be an improvement but wouldn't get around the issue of the insulating layer of steam slowing down the cooling process.

With parts as small and with as little mass (and therefore only capable of "holding" a very small amount of heat) as watch parts, I wonder how much of a difference there would be between using oil and water. I do like the idea of quenching between two heavy steel block to prevent warping, and I think that I would be inclined to use oil if only for the prevention of rust on either the work piece or the steel blocks.

 

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