Let me preface this by saying I'm a complete and utter novice when it comes to this art -- to the point where this question is actually asking what tool I need.
Using some standard brass 3/4" pipe, I want to resize portions of it down to 1/2", similar to this shape:
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Can this be done with, say, a mini-lathe? I was under the impression that a lathe was strictly for shaving down an item, but I've had someone else suggest it can be used to actually change the diamater in this respect.
If it is possible are there any structural disadvantages?
It can be done on just about any lathe regardless of size. If the lathe does not have a taper attachment then typically the compound rest is set at the taper angle and this is used to turn the taper portion.
This is a great example of the kind of question that is posed at too low a level. What is it you're trying to do? Are you trying to route power to an external building containing a swimming pool? Trying to get an old agricultural engine running? Making a custom brass instrument?
It may be possible to swage brass pipe down this far somehow, but my guess is it would have to be done at orange heat with special tooling on a large rigid lathe.
wrote: (clip) Using some standard brass 3/4" pipe, I want to resize down to 1/2",(clip) ^^^^^^^^^^^^^^^^^ Whoa! If you turn down a 3/4" pipe to 1/2" OD, will you have any wall thickness left? If you're thinking of spinning it and making the metal flow down to 1/2", you will need better advice than I am able to give.
This actually is correct -- good guess. :) As I've mentioned, I'm an absolute novice, so I'm not suprised I didn't supply enough information; I'll try to be a bit more specific -- here is what I'm trying to replicate or at least get something similar to:
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The body (lower part is 1/2" pipe) and the top part where it's most wide is 3/4" -- I don't think it's a conventional brass fitting or adapter, so I'm assuming it was either manufactured or somehow tapered into that shape. Hopefully this is a bit more information and the photograph will help.
That was my primary concern -- I didn't know if a lathe could be used to turn metal in this respect... 'bend' it to this shape rather than cutting it down. Which goes back to my original question, can I use a lathe to do this or am I looking for a different machine altogether?
regardless of the shape internally , you could machine this part on a lathe , with little trouble , the internal taper is a little tricky but not really
I have put a ball bearing set-up in a lathe, similiar to a single wheel knurling tool to roll thin material into shapes. The idea of reducing the dia. of tube may not work out to well. How about starting with the 1/2" tube, and plug the ends, then introduce air pressure in the tube and carefully heat it in the section you want expanded? I did this with an expansion chamber that was smashed almost flat and the results were way better than I expected. Low pressure and more heat is probably the safest.
Not sure what an internal taper is, but it's good to hear that it isn't that difficult. :)
It really depends on the success I have -- the instrument I'm making (an irish whistle) is broken into two parts, the body (which this is a part of) is relatively simple -- that tapered piece with an 8" length of tubing with specific sized holes drilled into it. That's the easy and relatively inexensive part. :) The harder part, the mouth piece, has a much more complex shape and requires me to bore out some delrin and lathe a plug with a windway cut into it.
I'd prolly try to get 25 or so to start with for my first run.
No, but that's another good idea! Being primarily a progammer, I have no clue where machine shops are around my area (Delaware), so I may have to look around.
While this sounds an interesting idea, I guess I'm looking for a technique to be able to duplicate with exact precision so I'm able to produce instruments all look the same. Although, when I get the equipment I need, I may try this just to see what comes of it!
It sounds as though you are planning to go into competition with Copeland, who makes the nicest tin whistles that I have ever tried.
Hmm ... as a programmer, this opens the possibility of using a CNC lathe to produce your parts. (Though it really helps to have experience with machining before you start with CNC, just so you know what works and what doesn't.
I'm a much bigger fan of a Burke whistle because it's sound is very pure -- more like a piccolo and that's my preference whereas Copelands have more of a 'chiff' sound which a lot of traditional players enjoy; it really is a huge matter of taste. Not to mention that I'm pretty sure Michael Copeland does this fulltime whereas it'd be more of a hobby (unless I show a real affinity for it). :) So, I wouldn't say I'd be competing against him, per se.
Just googling 'CNC Lathe' it looks they like are pretty huge, expensive monsters -- I really am looking to start this at entry level, just to see what comes of it. I'm definitely more of a musician than a businessman, so the large drive of this is coming from the desire to craft my own instruments... and it's nice to see that someone here has actually played a Copeland! (I also play Octave Mando, and Bodhran... picking up a 30-button anglo concertina for christmas -- saw your website, BTW... lovely Wheatstones!)
Thanks for the suggestions -- I'm learning quite a bit (mostly what I don't know ;p) and appreciate how helpfull you folks are here.
Machining that part would entail starting with stock thick enough to form the larger OD (outside dia), then removing metal both externally and internally to form the tapers and possibly the bore diameter. If the inside can be a straight bore rather than internally tapered, this is probably easiest -- though the resulting part might be a bit heavy and I've no idea how it would perform musically.
If I were making 25 or more of these, I would make an expanding mandrel so they could be made from 1/2" tube. In your case, have a machineshop make the mandrel. The mandrel would have several segments and possibly an extractable central cylinder so it could be removed once the shape is formed. I would anneal the tube, insert the mandrel, chuck the lot up in about any lathe, and apply a roller to the metal while expanding the mandrel. The action of the roller pressing the tube wall against the mandrel (with some force) will gradually stretch the metal to shape. Then collapse the mandrel, pull out the center and then the segments from the finished workpiece, and so on.
I think the workpieces would only take a very few minutes to make, once you had the mandrel.
I wear very large " L " plates for metalworking so my ideas may not be practical.
The internal swelling is the hard part and I think it would have to be made in two parts and joined.
If I were making it, I would turn a mandrel of the internal shape and then roll sheet brass around the mandrel in two parts, soldering / brazing each half at the join, removing from mandrel and then joining both halves together. If you have no lathe, I am sure one of the members would be able to make a mandrel for you. I have insufficient skill at lathe operating as I find it hard to get a smooth surface to my work and postage from Oz would be expensive.
The brass sheet would need to be annealed to make it easier to work.
Other members of this newsgroup are far more experienced than I am and will, I am sure, have better suggestions, or improvements to my idea.
HTH
Alan in beautiful Golden Bay, Western Oz, South 32.25.42, East 115.45.44 GMT+8 VK6 YAB ICQ 6581610 to reply, change oz to au in address
There is a variation I have read about being used industrially:
Make a two-piece external mold (of metal) that completely surrounds a piece of 1/2 inch brass tubing, with the annealed part of the tube lined up with the expanded part of the mold, and force oil into the tube, hydraulically expanding the tube into the mold.
The key is making the mold assembly strong enough that the hydraulic pressure won't blow the end plugs out, or spread the mold halves. If the mold is a split cylinder with two screw-on end caps, it should work.
The end caps would also have a fitting at each end that slides into the tube, and is sealed with O-rings to the inside of the tube. One fitting is blank, and the other has a port to admit the oil. These fittings are loose, and do not turn as the end caps are tightened, but are held against blowout by the end caps. The external mold restrains the tubing so it cannot expand enough to bypass the O-rings. Trim tube on lathe before expansion, to ensure a good fit in the mold assembly.
The slight relaxation of the brass after the pressure is removed should allow the expanded tube to drop out of the half-molds. If not, split the mold into three pieces (which will resemble pickles). Or, stick a steel rod through the tube and nudge it with a hammer.
Go to a shop that makes hydraulic hoses and ask about their swaging dies. (Some people say "swedge"). Those things reduce tubing to a smaller diameter to clamp the hose to the end fitting. Especially look at how complicated and expensive they have to be to do the job on material a lot thinner than brass pipe.
OTOH, annealed copper water pipe is pretty easy to expand or compress in a lathe.
Looking further at the design, I'm kind of boggled now... The ends of the piece are 5/8", but on the top end, just at the top of the expansion, there's something like a sheath that runs the length of the pipe to the end to allow a 1/2" pipe to fit in snugly (with a tiny bit of machining). So now, I'm starting to wonder if it was a brass pipe
1/2" in diameter, with 1/4" wall thickeness to turn both the inside and outside.
Heh, I might have to rethink this design a bit. :)
All the 3/4" pipe I've seen, if turned down to 1/2" will leave nothing but air in the half inch area. :-) Sort of like the 1" hole in a 1/2" peice. ...lew...
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