In almost all cases wheels and pinions are pre-riveted. Sometimes, if the wheel or pinion is damaged you will want to replace them. In newer models you can just order a complete wheel and pinion set, but this option is not always available if the calibre of watch is old or you are working on a restoration project and want to keep as much of the original as possible.
This is the pinion of the centre wheel from an Eta 6497/8 calibre. The wheel sits on the left hand side. The extended pivot on the right side is where the cannon pinion is fitted to. On the wheel side you can just make out a crown of thin steel, this is the part that you will later rivet down. You can also see from the top picture that the inside hole of the wheel has teeth which will lock with this crown.
Firstly you want to select the right sized hole in your staking set. Then you can use a spike to centralise it and lock the bottom plate in position.
You can put the pinion in place, making sure that it is sitting flat to the base and that the correct side is facing up.
You can push the wheel onto the pinion, it will make a loose friction fit but will be enough to hold it into position. You have to ensure that the teeth on the pinion’s crown line up with the teeth on the inside of the wheel.
The first stake you want to use will push the wheel down flat to the shoulder of the pinion. This needs to have a flat bottom and have a hole large enough for the entire pivot and shoulder of the pinion to fit through.
With the wheel set down flat, the crown I mentioned earlier is protruding through the top of the wheel.
The second stake you want to use will bend down the tips of the pinion’s crown over the wheel. For this you want a stake with a curved end with the hole big enough to fit the pivot through, but not the shoulder.
You can see that the pinion’s crown teeth are bent over the wheel slightly. This will hold the wheel in position but it will not be a strong rivet.
Now you want the final stake, which you will use to flatten the teeth that are now bent over. This will create a firm rivet and will hold the wheel in place on the pinion.
The finished rivet on the wheel.
The next stage is to poise the wheel. This is to check that the wheel and pinion are lined up correctly. You can test this by holding them in a figure of eight poising tool and turning the wheel with a brush. You can see if the wheel wobbles or not, and correct any misalignment by nudging the wheel in the appropriate direction.
This is another, more accurate, poising tool. You clamp the wheel into place and then entend and raise/lower the middle piece of wire. By placing the wire just above the wheel as you rotate it, you are able to see clearly when you spin the wheel if it wobbles at all.
The final stage is to burnish the pivots on the pinion. For this we are using a Jacot tool with a bow. Burnishing is where you rub material together until it becomes smooth, and in the process you harden the outside. Burnishing is useful as it makes the pivot hard enough to avoid wear, but because the inner core is still soft it retains some flexibility and so is less likely to break.
The Jacot tool has a levered carrier so that when you move the bow, which is twisted around the pulley, the wheel will move. You then want to select the correct size groove to fit the pinion in. For this centre wheel the pivot is the bearing surface immediately to the right of the pinion.
With the wheel setup and locked in position you will want to add a little oil, I’ve used winter green oil, and rub your burnisher across the top. The Jacot tool’s groove means that if you select 0.5mm, then you cannot take it below 0.5mm so you can be very accurate. As you pull the bow you want to push the burnisher, and then push the bow and pull the burnisher. You get in a back and forth rhythm where your burnisher moves in the opposite direction to the pivot. You can continue to do this until you feel no further friction, and so you can be certain that the pivot is the exact size you have set the Jacot tool to.