Reamers

[lebel409]

OK, before you guys go all Brown on me, I'd like to find out how you make long deep tapered holes.

This would be in brass, 9 or 10 inches long, .22 tapering to .56 or so. Seems too small and long for a boring bar.

Some of the inner diameter needs to be a straight morse #1, but after that I'm looking at complex shapes, parabola, etc.

Do you use a service to build custom reamers, do you make it yourself? I'm sure I could make something, eventually, but would like it repeatable and/or replacable...

I know a little about lathes and have a 12x36, I've not dealt with threading yet...

[Racey]

3 axis cnc, interpolating to cut the shape is what i would guess.....

For example Many CNC props for V-drives are not bored with a tapered cutter, they use a normal cutter and 'spiral' up and out of the hole at a very fine resolution, if you run your fingernail in the bore you can barely feel the machining lines.

[lebel409]

This would be for a trombone...that's why the bore is so small.

Ridges aren't a problem, sandpaper will smooth that...

I'm looking at a taper > a minor diameter, a long taper< (maybe parabolic) to a parallel bore.

I'd need to be able to change it a bit...open this or that to customer tastes...so reamers would be the best option I can think of.

How would a CNC get into a 9" long hole .22 in diameter?

[Yellowboat]

trombones are made out of sheet brass.

[lebel409]

trombones are made out of sheet brass.

Mostly...been fixing them for 25 years.

Mouthpieces are turned, many pieces hydraulically formed, formed on tube drawing machines, pot metal, valves are milled...lots off different materials and processes.

I'm looking at making a piece that goes inside the slide that the mouthpiece fits into. If you look at a trumpet, you can see that the tubing tapers from the mouthpiece reciever to the tuning slide...It does the same thing in a trombone, only you can't see it because it's inside the slide.

[Yellowboat]

wouldn't it be easyer to turn a mandril down to the correct diameter and then form a peice of sheet around that. then refine it by spining it on the lathe?

[lebel409]

That's kinda what they do now. Mass (especially in the first part of the horn) focuses the sound better. So by adding a machined piece instead of a thinwall tube it'll change the way it plays. Too much kills it so the exterior could easily be turned down...if needed.

Think about a mouthpiece...if the rim is uncomfortable, turn it down. If the bore is small, drill it out. Hard to do with a thin tube that will fold up on you...harder yet while it's still in the trombone.

[Racey]

I think the mandrel option is the best bet for this application, it's too thin and flexible for standard machining i'd guess, that's why it's drawn not turned..... I dunno with instruments so many factors affect sound quality, i wouldn't know where to begin ;)

[lebel409]

"standard" thicknesses are .02 for the venturi tubes. Slide tubes are more like .009

However the taper goes from .22 to .5 or so...so lots of room for more meat on it. A big difference when you use a .035 walled tube...so I'm going for solid:D

Any takes on reamers?

[Racey]

"standard" thicknesses are .02 for the venturi tubes. Slide tubes are more like .009

However the taper goes from .22 to .5 or so...so lots of room for more meat on it. A big difference when you use a .035 walled tube...so I'm going for solid:D

Any takes on reamers?

Maybe turn and machine your own reamers from tool steel? it just seems to me that when you get down to brass that's only 20 or so thousandths thick it's gonna get soft to turn, it may want to lock up and twist.... I would imagine that trying to have custom reamers made would be VERY expensive....

Also is the fact that it's machined from billet going to affect the sounds of the instrument? Cymbals for example are turned from specially forged billets, that way they have a certain amount of internal tension and give the proper resonance, they aren't drawn, are brass wind instruments the same in that respect to the metal being used? Like i said i know little to nothing about instruments, but i do find it kind of fascinating, so these questions are more so to gain some personal knowledge, not to quiz you about what you are doing... :thumbsup

[lebel409]

I'm all over it... Cymbals are made of (mostly secret) bronze alloys. Then they are hammered and annealed many times to get the shape and sound, then spun which work hardens the bronze and adds high overtones.

Brass instruments bells are usually sheet brass, bent to a funnel and brazed, then annealed and hammered, then spun...similar to cymbals...some are then annealed, changes the way it responds/projects.

Bent tubing used to be annealed, filled with lead, bent, reshaped. Then they went to pitch to fill the tube. Now the factories use soap/salt water, freeze the tube and solution, bend it and pour it out. Some use an external form and draw a lead slug through that will deform as it forces the tube to the form.

The parallel tubing is all drawn, but tuning slides are heavy compared to trombone slides...think about a 28" tube with .009" thick walls that has to be STRAIGHT. No room for bows, bends, dents, ovals... I use a grade A 18X24 surface plate to check them.

Here's the deal on brass instruments VS struck instruments...the struck ones have a set of properties, materials, diameter, mass, density...while wind instruments use all these and a shaped vibrating column. There's no doubt that the air column (internal shape) is the most important factor, but there's a lot of anecdotal evidence that mass effect the sound also. So if mass effects the sound, so does material.

I think this is why I like boats...you either picked up some speed or you didn't, it either works or it broke. Instruments have all these damned opinions...which may or may not be right for someone...

[RiverDave]

With wall thicknesses that thick it's going to be difficult to machine it without a whole lot of specialized fixtures / etc..

lebel for something like this I have a guy.. It's one of those I don't ask questions, he doesn't give me answers, but he gives me a part, the part is complete and to tolerance..

If you can provide me a legit drawing of what you're looking for / qty / etc.. I'll get it quoted for ya.

RD

[lebel409]

Thanks Dave!

I'm sure it would be a set (or 3), not a single reamer...

Let me work on it...