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Why a castle rivet?

by Jordan Ficklin

First, totally unrelated to the title of this post I want to add that I see watches come in waves, just like J. Edwards points out in his last post. It just seems to be the way it is. Also, ideas for blog posts seem to come in the same fashion.

One of the best ways to learn while working is to ask yourself the question, “why?” The Rolex oscillating weight axle is held to the weight with a “castle rivet.” This is a rivet with alternating secured and unsecured portions. This is the tool for making such a rivet.illustration2 Today I asked myself why? The answer I came up with: A castle rivet is ideally designed to prevent rotation. Because the metal gets pressed down in alternating sections it causes little shoulders to form which keeps the weight from rotating on the axle, besides just keeping the two attached to each other.

This realization led to the next question: why don’t we use castle rivets on balance staffs (also exposed to lots of rotation.) The answer comes in two parts: 1.The area of the rivet on the balance staff is so small you need the entire surface clamping down just to keep it in place. 2. You need to press the hairspring collet down on top of the rivet so you need a flush surface.

Keep asking why and you’ll keep learning.

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