Reducing brass tubing

Macabre of Auchterloonie wrote:

I done this sort of thing on larger stainless tube, 20mm and 25mm about
1.6mm wall. I turned up a thick collar with the tube OD bored in it and
a lead in taper then cut it in half and mounted one in the ram of my fly
press and the other on the base. The tube was then repeatedly squeezed
and rotated and it could be quickly reduced in size. You might try
something similar and if you don't have a press then maybe a vice would
do, likely somewhat slower though.

Otherwise I've reduced the size of short lengths of tube by pushing them
through a sizing die, the length being short enough not to buckle under
the load. A good lubricant helps a lot. If the tube is long and likely
to buckle you might need an internal and/or external support.

David Billington wrote:

No, I don't have a press, but thanks for the idea: make something=20
similar to what you suggest, but only pierce the length only on one=20
side. If necessary, an hydraulic jack could be pressed into service.=20
(Sorry...)

Keeping the alignment wouldn't present a problem then.

<thinks> Or, take two blocks of gauge-plate and peg them together; place
in drill-vice and drill, cut and ream the die at the junction of the=20


Yes, I've resized, necked-down and otherwise manipulated brass cases for =

obsolete arms in the past, so I have a good idea of the culpabilities of =

sizing dies. Doing so with 3" lengths of open-ended tube (@ £3.15/foot)=
=20
makes me reluctant to go down that route.

The split die seems favourite to try. I do have a big vice (but don't=20
talk about it online...), and there's a general auction next Saturday in =

a nearby country market-town, and I'd be surprised if there isn't an=20
hydraulic jack amongst the deadstock lots.

Otherwise, they're not expensive to buy new.

I've been postponing this job now for several <whisper> years=20
</whisper>: Now I shall lie awake for several nights=20
fretting^h^h^planning...

--=20
Old Nick

On 26/05/2012 14:57, Macabre of Auchterloonie wrote:

I have never had to do anything like this but ever the optimist how about---
Replace the knurls in a caliper type knurler with plain discs with maybe
a very slightly rounded outside face.
Make up a steel tapered mandrel to the required length and taper with a
parallel section a push fit in the tube.
chuck tube and mandrel in a 3 jaw chuck.
Pinch the rollers onto the tube at the chuck end and whilst rotating
traverse slowly to the other end, traverse back apply more pinch
traverse etc.

Three rollers would be better but I think this explains the concept

--
--
Richard

Richard Edwards wrote:

If I had a lathe with a chuck...

Still looking for a very small chuck I can graft on a Super Adept...


Well, I no longer have any knurling tools, nor a working lathe of any size.

Unless someone has a better idea, Savid Billington's solution is
favourite ATM.

It has occurred to e that a split die could be made using NC spark
erosion - if it doesn't cost silly money.

--
Old Nick

Richard Edwards wrote:

Have just remembered the bearing balls.

I can't remember where they came from, or even when they came, hey've
been around so long, but amongst my 'may cumminandhi
even if I never use it' box I have four one inch bearing balls, each
with a three sixteenths axial hole through it, and, surprisingly, I have
laid my hands on them.

The knurling tool and tapered inner steel core suggestion is coming back
into play.

Three of three-sixteenths inch silver steel bar, hardened, and immersed
in molten lead which is gathering a straw-brown film over it will temper
the steel to spring quality.

The spare Super Adept bed, head and tailstock (courtesy of Jim Guthrie)
might acquire a special chuck, just for tapering and/or moulding brass
tubing.

Watch this space: I expect you can see how (or if?) my mind is working...

--
Old Nick