Since we haven’t had a ‘Whistle Tech Talk’ in a while, I thought I’d share this useful bit of information with prospective whistle makers.
The bevel on the fipple block where the windway exits into the window is a critical factor in tweaking the voicing and strength of the lowest notes.
That much is fairly common knowledge, but it is worth mentioning the additional fact that the bevel depth must be increased proportionately for lower keys… what works very well for a high D won’t work very well for a low D.
You can control the level of ‘chiff’ and the strength of the lowest notes to a significant degree by experimenting with different bevel angles and depths, so tweak away and have fun! 
Actually the both the block ‘floor’ and the windway ‘roof’ get the bevel or chamfer.
I chamfer the roof on my Low whistles but the roof is not as pronounced as the floor is.
You are right about it’s impact on sound purity. These cuts help form the top and bottom spread of the ‘windsheet’.
Hi guys, is this bevel your talking about at the end of the windway, making a sort of short expanding section?
I have Indian Whistles in which the front of the block slopes outwards (towards the bottom end) from the windway to the wall.
Over the past couple of years I’ve been collecting de-pithing Elder (Sambucus nigra) and have enough to start making whistles, how do you cut the fipple with a knife or a chisel?
TTFN
John S
On mine, it’s only the block that gets this treatment. Also, instead of a flat chamfer, mine are rounded to a small radius. I just stick the fipple in the lathe chuck and touch it with a file as it rotates. I start with a very minimal chamfer. Then, once I’ve filed the ramp, I test the sound and response and bit by bit increase the chamfer until it plays the way I want it to.
I agree regarding adjusting the chamfer for the best sound. I do the top section with the help of an Exacto knife, the bottom with files and sandpaper.