We know what a balance wheelBalance Wheel The balance wheel is a component of a mechanical watch movement that oscillates at a consistent rate. It receives a small impulse from the pallet fork, which is part of the escapement mechanism. The balance wheel is connected to a hairspring that controls the rate of oscillation of the balance wheel. The balance wheel and hairspring work together to keep accurate time. The oscillations of the balance wheel drive the timekeeping functions of the watch. The balance wheel is a crucial component of a mechanical watch movement. [Learn More] is by now (if not, read this). But how does one make the necessary adjustments to this very essential component, the regulating organ, in a watch movement?
The featured image (courtesy H. Moser & Cie) is a blown up image of the balance wheel. As you can see there are little tiny screws on the balance wheel. That is one (haute horlogerie) way of finetuning the balance (poise) of the wheel.
However, that is certainly not the norm for most balance wheels out there. On mass produced and cheaper movements, you will likely not find any screws, the adjustments are instead made in a robotical fashion by laser etching. It’ll burn the balance wheel in just the right places to shave off just the right amount of material in order to get to the best possible balance. The difference between both methods is easy to spot as shown below: