One of the most challenging parts in making whistles (and I suspect lots of other instruments) is keeping the corners and edges sharp. The fipple – the edge the airstream is directed onto – for example, is one of the most important parts in the formation of a good tone. Also, the edges of the tone holes are the extremely influential with tuning and intonation.
But by their very nature, edges are exposed, making them vulnerable to getting rounded off. From a makers perspective it’s awkward because if we didn’t have to maintain the edges, we’d just be able chuck the assembled instruments in an automatic polishing machine and collect the beautifully shiny whistles an hour later. In a similar vein, it’s always been said that you can tell the quality of a flute by whether the keywork has any hard lines or edges – on the cheaper models everything’s been rounded off in the finishing process.
Obviously edges need to be deburred and finished so as to be safe to touch, but rounding out the tone-hole edges on whistles means that some form of ‘indiscriminate’ finishing has been used, which attacks the edges – pushing sandpaper or a scotchbrite pad up against the body as it spins on a machine might be an example. The difficulty here is that, although it gives a good overall finish to the eye, it rounds off the edges, and by the very nature of this kind of abrasive process, it’s difficult to do consistently, with these inconsistencies then work their way through to the tuning and intonation.
It’s one thing to identify a problem though, and an entirely different matter to solve it! It’s also true that soemtimes the answer might’ve been starring you right in the face – for ten years! Thankfully focusing in on this has produced some good processes and techniques, and it’s something we’ve made good progress with.