Hiko Mizuno College of Jewelry produces many talented watchmakers every year. One piece that particularly caught the eye at the 2025 Graduation Exhibition was the mechanical metronome "Tempo Rubato" made by Raku Okada.
The world's first wristwatch-style mechanical metronome, completed by the up-and-coming watchmaker Raku Okada. Not only is it the smallest in the world, but it also allows you to freely change the BPM. As you can see from the photo, it is already perfected enough to be used as a commercial product. Manual winding (Cal. TempoRubato). 7200-14,400 vph. Stainless steel case (39.5mm diameter, 13mm thick). Water resistant for everyday use. Not for sale.
Text by Masayuki Hirota (Chronos-Japan)
Edited by Yuto Hosoda (Chronos-Japan)
[Article published in the July 2025 issue of Kronos Japan]
The world's first wristwatch-style mechanical metronome
Raku Okada, a student at Hiko Mizuno College of Jewelry, completed an amazing device for his graduation project. This was the world's first wristwatch-style mechanical metronome, the "Tempo Rubato." Its unique features include being the world's smallest mechanical metronome, the ability to freely change the BPM even while the metronome is running, and the fact that it is actually usable. Okada, whose hobby is jazz drumming, actually tested the shock resistance of the Tempo Rubato while wearing it on his wrist, so this is no mere gadget.
Operation is very simple: Press the bottom left push button to activate the metronome, rotate the bezel left and right to adjust the BPM (120-240), and rotate it right to wind the mainspring.
What made this possible was the idea of using the anchor of a mechanical watch as the hands of a metronome. The idea of being able to change the BPM by moving the weight connected to the rotating bezel and hands up and down was also unique. The load on the mechanism seems large, but Okada solved this by using ball bearings made by MinebeaMitsumi in areas where large torque is applied, such as the up and down movement of the axis of the hands.
What impressed me was the cleverness of the packaging. With a diameter of 39.5mm and a thickness of 13mm, it sits quite comfortably on the wrist. And the rotating bezel has a restrained feel that makes you want to touch it for the sheer pleasure of it. Honestly, who would have thought this was a graduation project?
Even if you're not in the music industry, if you're a fan of mechanics, you'll definitely want to get your hands on the Tempo Rubato. This is merely his graduation project, but Okada is considering releasing it commercially in the near future. Let's be very happy that there will be another generation of watchmakers with promising futures!
