A Guide to the Sinn U-Series Bezel (rev. 0) 2011 rationaltime This discussion applies to the bezel of the Sinn U-series (U1,U2,UX) watches. This is a Sinn U1 with a tegimented bezel. It is also made in a version with a hard, black Coating. Sinn calls the black bezel SDR, German for Schwarz Dreh Ring. The bezel can be rotated only anti-clockwise. It turns with a ratchet action, and has 60 steps or clicks per 360 degree rotation. On the perimeter of the bezel there are four screws that look like this one.
To remove the bezel we will loosen three of the four screws. See this Sinn screwdriver/pusher tool that came with the watch? That tool is not meant for bezel screws. It is too big. Put that tool aside. A smaller screwdriver is needed. At Home Depot I found This General Tools screwdriver. The tip of the screwdriver blade may need some size adjustment with a whetstone. There are four screws in the bezel at 0 (index), 10, 30, and 50. Leave the screw under the triangle at 0 alone. Try loosening the other three screws. Don't force the screws. It might necessary to release the thread locker with hot water. Do not remove the screws. To prevent loss just back the screws out until you can see the bottom of the head like this.
Now place the watch dial up, and with a little wiggling lift the bezel straight up off the watch. This is what you see. Notice the three pins at 4, 8, and 12. Those pins give the bezel a ratchet action. The pins can be lifted out with forceps if you like, but be careful to not lose them. Push on the pins to test the springs underneath. You might give the pins a little lubrication. Silicone grease seems safe, but other things might work. Looking at the bottom of the bezel we can see a ring of teeth, a continuous saw tooth ramp. These teeth form the ratchet. Notice there is only a stop on one side of each tooth. There is no centering action.
What holds the bezel in place? Look at the bottom of the bezel. There is a flat bronze spring held in a groove between the bezel teeth and the top of the bezel. There is no need to remove the spring unless there is corrosion. I have removed the spring here for illustration. To remove the spring use a toothpick and pry one end of the spring inward until it clears the lip of the groove. Then pull out the spring without bending it very much.
This is the view from the top. Note for reassembly the spring has to be inside the bezel groove and not as shown below. Now we can see how the bezel is retained on the case. The flat spring fits simultaneously in the groove on the case and the groove in the bezel. The bezel screws compress the spring radially to hold it in the case groove. The bezel screw under the triangle only keeps the spring from rotating. That is why we did not loosen that screw to remove the bezel. When the bezel is rotated it slides on the bronze spring. The tension is set by the springs under the case pawls and the ramps on the bezel teeth. The bezel screws only hold the spring in place. The screws do not adjust the bezel tightness or the bezel clearance. The screws do not retain the bezel. Now examine the bezel. It is a single piece of hardened steel. There is nothing to break. It would be difficult to have a bad bezel. The marks are engraved in the top of the bezel. The only insert is the luminous triangle. The bezel won't pry off or fall off. This robust design is satisfying. Something could go wrong. If you swim in a lot of fine sand or silt that stuff could get into the pawl pins and springs. It could cause them to get sticky or jam. If you do that much you might need to clean that out occasionally.
All right, now reassembly. Make sure the spring is in the bezel with the gap at 12. The bezel screws should have the screw heads only protruding from the case, like this. We discussed bezel retention. The screws do not hold the bezel on. They don't need much torque to tighten them. To keep the screws from falling out we use thread locker. You can use the blue stuff that came in the plastic bottle with the bracelet. I used clear acrylic applied with a toothpick. Hold the bezel over the watch and move it straight down onto the case. The bezel should fit all the way down onto the case with only slight wiggling to get the spring by the shoulder on the case. There should be almost no gap between the bezel and the case.
Then apply thread locker and gently tighten the screws. All back together now, it should look like this. 2011 rationaltime There is something satisfying about the construction of the Sinn U1 bezel. I suppose you can not get a feel for that by looking at the photos. Like most activities you have to try it to feel it. Still, from the description I hope you can get the idea of what goes on here. Any questions? Thanks for reading. rationaltime