What is a Column Wheel?

A column wheel is the wheel/gear which coordinates the start, stop and return to zero functions of the Chronograph hands.

In a standard quality chronograph, the column wheel is replaced by a system of cams. So, in oder to operate the chronograph, cams are needed to be layered in two pieces. One layer receives the input from the pusher, while the other transmits the motion to the clutch, where the connection between the chronograph mechanism and the movement is achieved .  the cam also blocks the reset mechanism while the chronograph is in operation in order to prevent movements jamming.

A column wheel has exactly the same function, but is built in a way to provide more accurate, more precise operation, which can be noticed through the motion of the crisp and precise pusher action. Where the cam is made of two layers of metal, the column wheel is a single piece, and usually needs high precision machining to manufacture.

Beyond the precise feel, a column wheel provides more benefit. It is commonly know that cam-actuated chronographs experience slack when started, this is usually noticed when the chronograph seconds hand skips forward, but this is thought to be more an issue with the use of horizontal versus vertical clutches (where the chronograph’s mechanism meshes horizontally rather than vertically with the gear train), with the more common cam-actuated chronograph typically featuring a horizontal clutch and the column wheel variety a vertical.

What is a Mono-Compax?

Mono-compax is the designation for a watch dial with only 1 subdial, a register that displays timed minutes by pushing the upper chronograph pusher, the subdial is usually located at 3 o’clock. This type of display appeared for the first time in the early 60th in the Aquastar Deepstar and is now being used again in the 2020 Deepstar.