Measuring the inside of wind instruments accurately is really tough. Most calipers don’t reach, and most bore gauges don’t cover the necessary range. I had no luck finding anything that would work for sale.
My solution was to print my own! Each rod, and at the smaller sizes, sphere, has a hole for a 3mm by 3mm cylindrical magnet. These were modeled with the very end surface of the magnet at the widest point (the measuring plane), so when marking my depth stick all I have to do is start at 3mm.
The depth stick is a 3mm steel rod, which goes through a hole in a small sheet of plastic to mark flush with the end of the instrument. Then, a series of depths and diameters can be generated to reconstruct the bore profile. Accuracy, especially at the narrowest points, is critical, and so the increments become more numerous the smaller the measurement.
Now I’m all set to accurately and precisely measure any bagpipe, flute, oboe, or recorder I might come across! Thanks to the low hardness of the Color resin, I don’t have to worry about scratching anything.