WS 9: Replacing the main spring of a Rolex Caliber 1570

The factory spring load is considerable and inserting it into the barrel is not easy. As it happens easily, the insertion of the compressed new spring into the barrel did not work the first time. The spring unwound with a whishing sound and flew across the room.

We used the chance to get a nice picture of the new and old damaged spring which we probably would not have otherwise. The dark area below corresponds to the white rectangle on the previous picture and shows the damaged geometry.

With some extra effort and resulting hurt finger tips, Rob managed to wind the spring holding it firmly with a pair of brass tweezers and also managed to replace it into the barrel safely. Mainsprings have different ends (on the left side in the picture below). The barrel arbor has a stud which grips into the opening of the spring's end. On the right hand side, you see that there is a tail connected to the free end. This stiff end makes sure the spring does not unwind in the barrel. The friction between this end and the barrel wall keeps the spring wound. You can clearly see that the old spring below has a slightly bent up end of the afore mentioned tail. Whether this was factory made or whether a previous watchmaker try to work around a spring replacement is unknown.

How to oil a spring before the barrel cover is closed, is rudimentary explained on this page and also in this summary. For a thorough oiling instruction, please consult your watchmaking literature or the service manual.

Thanks Rob for elegantly jumping over another unexpected hurdle.

A spring winding tool is a simple installation with a handle that will allow you to wind a spring. It comes with dies in several diameters to match different barrel sizes. Winding a spring with such a tool is easy. Winding it by hand and inserting it is something I would not yet want to try.

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New spring on top, old damage spring below. The darkened area shows the damaged area of the old spring