William, this is hugely impressive--you clearly have advanced machining skills and excellent problem-solving techniques! I think your solution is elegant, though it does seem to be confined to making straight tapers, is that correct?

When I made my first "Irish" flute (and this might be repetitive if you've read through the older threads on reamer making) I tried to make my life easier by doing a straight taper, which was a clear departure from the data I had gotten from Terry that came from his original Pratten flute. The straight taper made a really nice flute, but my flutes did not attain that next plateau until I returned to the original data, which indicated a bore with a fair number of "bumps" and "dips" along it's length. Past flute makers definitely used a "wiggly" bore to enhance tuning/harmonics, and even though many of the perturbations are quite small, the cumulative effect is profound.

Thanks for nudging me to dig out all my files on bore profiles as they relate to intonation and response (even some from the 80s and one from a college course I took on musical acoustics in the 70s!) and go over my thinking once again and from the beginning.

1. I had thought that small "perturbations" in bore profiles were unintentional. When I first got interested in making a flute, I obtained drawings and other measured data sets related to one particular 18th century flute maker. What I noticed when I laid graphs on top of each other was an "average" that I took for an original intention--or even a peek at the shape of an original reamer--and "perturbations" that looked like a combination of wood change over time, inaccuracies in measurement (I have two drawings of the SAME flute based on measurements taken by different individuals at different times that contradict considerably!), and, speculatively, bore alterations made by someone later. I even took the trouble to measure a couple of bores myself at different temperatures and humidity levels and got different graphs from the same flute using the same measuring tools set up on the same bench!

2. When measuring modern reproductions, I've noticed something very close to the average I saw when superimposing graphs.

3. Years ago there was a minor fad among trumpet players that involved having factory leader pipes (the first section of tubing after the mouthpiece) replaced with custom leader pipes with stepped bores. The guy making the stepped bores had good marketing copy and lots of fancy brochures with intonation charts and testimonials from a few good players, but it all died down after a while and everybody just went back to their more traditional leader pipes that were basically a straight taper or variations on a parabola. That episode stuck in my mind and influenced me when I saw small variations in flute drawings. Now I'm going to drag out all my old files and try to re-think everything.

I'm new to this forum. Would you be so kind as to provide links to other discussions here about reamer making?

Thank you sincerely,

Bill

I have to admit I don't understand how you get "perturbations" in a ream if you are using a tapered reamer. Surely everything "behind" the widest point in the taper is going to be as wide as the widest part of the taper?

Nice mill work! And I like your support solutions (keeping the work supported to prevent the vibration is such a crucial part of it). I'm curious to see how you get along with that reamer design. I recently made a couple of reamers using that same design and they did not behave well for me. They showed a strong resistance to cutting--they didn't feed into the work very well for reasons that I'm still trying to puzzle out. I've made a bunch of different reamer designs over the years, and only recently tried that design after getting a schematic passed along to me that came from Rod Cameron. I was expecting great things and had the opposite experience! I still feel that there is some gap in my assessment of the problem, because it should work great. The fact that it doesn't makes me think that I'm missing something..

As mentioned in another thread, this reamer warped badly. At least badly in this amateur machinist's mind: almost .100" TIR. I think I'm going to throw a dividing head on the mill, chuck up another tapered blank, and try making another reamer with two or maybe three cutting edges. Perhaps symmetrical removal of material will keep the warpage down to something I can live with, something under .010" TIR.

Edit: There's a YouTube video somewhere showing reamers in use at a major European recorder factory, can't remember which. Freeze framing the video is how I decided on this design. I wonder why they chose it.

Well, you might want to make some cuts with your warped reamer first to see how it behaves. As I said, warpage is normal, and if not extreme it shouldn't cause any problems. Mind you, I've never done any systematic tests to determine this. But I have measured the bores of flutes that I've cut with warped reamers and they data points are where they should be. I might do some quick measurements on a larger sample of the flutes done with these reamers to see if there is any measurable effect caused by the warp.

I've enjoyed your pictures and description of your approach. It looks basically sound to me.
Nice work!!

Am I correct in assuming that the warping you refer to occurs during the milling process,
and not during some subsequent hardening process? The rest of my post assumes this to
be the case.

I wonder if the lack of lateral support is allowing the reamer to be bent slightly by the lateral
forces of your asymmetrical milling strategy. As the slot is being cut there will be significant
forces pushing sideways as well as downwards. Perhaps this is the source of the warping?

I use a slightly different approach to produce the cutting edges on my reamers. Specifically, I
use a ball-end mill, centered over the reamer and cutting downwards. The section of reamer being
milled is supported both vertically and laterally. The lateral support being provided by disposable
aluminum plates that are held in the jaws of a vice. The vice is periodically moved along the reamer.
It takes many shallow cuts to complete the process.

Here are a couple of pictures to illustrate this approach on a very long reamer:





This approach produces nice sharp cutting edges which can be periodically resharpened using a
diamond plate or sharpening stone. Note, with this approach you have to be careful not to cut beyond
the half-way point. Protecting against this takes a little more careful thought than when producing
a D-shaped reamer, because the height of the intersection of the curvature of the ball-end mill bit
and the outer surface of your reamer changes over the length of the reamer. The trick is to start
above center at the narrow end and work toward the wider end.

I just mention this because it is easy to destroy an almost finished reamer if you realize this too late. Don't ask me how I know this!