Seamless Pipe
Dear Sir, I want to to reduce my tube from 13mm OD with wall thikness
of 1.25mm as i want to reduce the size of tube to 7 mm & wall
thickness to 0.60mm. I already have a 14 feet long draw bench please
tell me the complete step to reduce the size of tube.
I generally need 3mm tube to 7mm.
Awaiting your reply.
Please answer the following questions first before we can help you.
Drawing tube to od size is not difficult.
When you do so the wall thickness does get thinner, but not by a
lot.
Drawing tube to a specific od and halving the wall thickness is
something else.
It is most unlikely that you will be able to do this without the use
of an internal mandrel over which the tube is drawn.
You will need one of these for each draw plate hole size. This has
to be held by another headstock clamp to position it just in front of
the draw plate hole and is on a high tensile wire extension longer
than the tube you are drawing. It has to be strong enough to
withstand the draw bench pull
So assuming you can get all the tooling together, you will need to
experiment.
Depending on the answers you give to the above you may find it may be
cheaper to scrap the metal and buy it in the sizes you need.
My first reaction is to ask: can you not get a tube nearer the
dimensions you need? I will make a plan, drawing to explain how to do
this. However you will have a problem as the wall thickness has to be
reduced from 1.25mm to 0.6mm which will require internal and external
reduction of 0.65mm to achieve your required measurements.
You will need a very strong and powerful drawbench and a lathe to
make a tool for the internal reduction and taps and dies to secure
the tool to a length of piano wire or some high quality steel wire,
say, 2mm.
And some patience! It will take me a bit of time to do the drawing.
It is not impossible.
David Cruickshank. Australia
Hi
The simple technique that I use to make relatively short pieces of
tube 30cm/ 12inches is as follows;
Fully anneal the tube and while it’s still warm touch the one end of
the tube with candle wax ensuring it runs from the other end, you
just need a little for lubrication.
Take a high tensile steel wire of the diameter that you want achieve
when the tube is at desired size. The wire should preferably be
polished and at least twice the length of the tube, as the tube will
grow in length as you reduce the outer diameter.
Insert the wire in the tube, crush or hammer the a lead on the front
end of the tube to hold the wire in place, I usually allow two
inches/ 5 cm of wire jutting out from the leading edge of the tube as
I have known it to slip back into the tube. I crush my tube leads in
the wire rollers of a rolling mill.
Draw the tube through the necessary draw plates until you get to the
outside diameter you require- wire diameter plus double the wall
thickness. Reverse the tube in the draw bench and reverse the draw
plate using a hole that just allows the wire to pass. Pull the wire
out with the draw bench.
Regards
Mike Kersley
I agree with Mike Kersley when I am drawing down small diameter tube
in short lengths.
However the question asked concerned a huge deminuation from 13mm to
7mm tube with a wall thickness of 1.2mm. To me extreme, and I agree
with Dar Sheldon, I think it was, who covered points I made offline to
the questioner along with drawings and instructions on how I would
tackle his problem. Though I did point out that it would be far more
sensible to get tube of the diameter he was going to use. In
correspondance with the questioner I got the impression it was the
only material he could get.
He did not divulge the metal he was working with.
Being in Australia my posts are always 24 hours late, I am obviously
on the wrong side of the international date line! I will post my
drawing and instructions to gnoksin so maybe they can be of use to
others.
David Cruickshank (Australia)
jewellerydavidcruickshank.com.au
Sorry re my previous post, just now.
It should have been Ted Fraiter, not Dar Sheldon.
I would appreciate it if this could be changed in your editing
process.
David Cruickshank.
Firstly, I will say that it would be better to have tube drawn to
the sizes that you need for your work as this is a difficult process.
I presume you will be doing a lot of work starting
with this size tube to make this a worthwhile process.
Secondly, as you probably know the wall thickness will increase each
time the tube is reduced in diameter, therefor two processes need to
be combined for each drawing.
To achieve this duel process it is necessary to:
have a very strong drawbench, belt and drawtongs.
You will need to have some polished tool steel plugs made,
drilled and threaded, and have some strong high tensile steel 2mm
wire, longer than the tubes length, to be threaded at one end to be
screwed into the polished plugs. The plugs must be highly polished
and lubricated.
I would suggest that you look at your draw plate and count the holes
from the starting hole, that is, the next hole under the 13mm hole
then count down to the 7mm hole, (and the 3mm hole) Assuming there is
a 0.5mm reduction between each hole, that gives 12 stages from 12.5mm
down to 7mm
At a guess I would make 6 polished plugs of decreasing diameter and
use one for each second drawing. It may not be so simple however.
You may have to make more plugs, one for each hole.
Experiment first with a short length of tube.
Process.
Anneal tube and taper 25mm + of tube to fit through lubricated
drawplate.
Screw the threaded end of the high tensile wire into the largest
polished plug.
Insert largest highly polished plug into annealed, lubricated tube
till the largest plug meets the tapered part. Then draw about 2mm of
tube through the hole till you feel the plug is approx held centrally
in the drawplate hole. See illustration.
Secure the other end of the wire so it cannot move as you draw the
tube down.
As I suggest you may have to make a separately sized plug for each
hole.
Look at the figures for 6 plugs:
External diameter 13mm with wall thickness of 1.25: so that is 13mm
minus 2x 1.25 as there are two X wall thicknesses to be considered,
so, 13-(1.25 + 1.25)=10.5 So the first plug needs to be slightly
smaller say 9.5mm at a guess, and so on. So for 7mm external
diameter your final plug will be 5.8mm for a wall thickness of 0.6
7-(0.6+0.6) = 7-1.2= 5.8
This will require a lot of patience and attention to detail as each
drawing is done.
Best of luck
David
