Part 1 of 8
Warning: Long multi-post starter to this thread… and some folk may prefer to be spending their time out in their workshop turning wood than engaging in pedantic stuff about flute profiles and names… :~}
The focus of this thread is neither turner preferences for one flute profile over another, nor is it about which flute profile might be better suited to a particular grind for one use or another.
My focus here is entirely on flute descriptors in order to reduce the confusion that I’m seeing over those in our woodturning community.
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Elliptical
Back in the early 70s when I began woodturning the flutes on bowl gouges had simple names like shallow and deep, which were easily understood. I can’t recall anyone giving the flute on the deep bowl gouges any other descriptor than that, but looking at the flute on the forged bowl gouge that Peter Child included in his 1970s book it might have been called elliptical…
And here is how Roy Child (Peter Child’s son) drew that elliptical flute profile that they were using back then in his later 1999 article http://www.peterchild.co.uk/info1/sflute.htm
There was then a period when elliptical was more widely used to describe a flute profile that had a continuously changing curve and Henry Taylor Tools described the gouge that they made to Roy Child’s design as having an “elliptical flute cross section”, which they called the SuperFlute. The ellipse is a precise mathematical curve derived from Conics and where a flute is elliptical it would be appropriate to call it that, but few are.
Here is how an elliptical flute would look in a round bar…
Roy Child himself neither named his flute design the SuperFlute nor described it as elliptical. In his own words he simply described it as follows, “it has a large radius at the sides blending into a small radius at the bottom of the flute.” Here is a diagram drawn by Roy of his flute profile design alongside the SuperFlute made for him by Henry Taylor Tools…
So, as can be seen, the Supeflute is neither a true ellipse (as specified in Conics) nor is it a parabola (more on those later), although it is much closer to a parabola than some bowl gouge flute profiles that have been described as parabolic. It is in fact closest to the catenary profile as seen in the example of a chain suspended from two level points or arches like the St Louis Arch that might be seen by some of you on your side of the pond.