Hipshot Buttons, Sperzel Machine Heads – unfortunately, they’re not compatible.

The Hipshot buttons are around 0.1mm too small to fit over the Sperzel posts. Also, the Hipshot screws have a lower thread pitch.

You could make the Hipshot buttons work by modifying the button post (like this RISA Ukulele for example) and using the original screw. The problem is that it’s messy and doesn’t guarantee a perfect fit.

You’re better sticking to Sperzel’s own range of buttons instead. Albeit limited, the options available will give you the desired custom look and the certainty that they’ll fit.