|
Alec and Emile,
I've done similar boring operations with a steel
shaft, two bearing flange blocks, a large electric drill with slow RPM's, a
hydraulic jack and a welder. The hydraulic jack can be replaced with a
screw jack, or even a piece of threaded rod. Basically it's a fly
cutting method of machining a diameter.
Mount each flange block to a plate you can
tack weld to the part you need to bore. Tack both plates so they are true
to the centerline of what you want bored and insert the shaft but don't
lock it in the bearings. The shaft needs to slide through the
bearings to act as your feed system. Weld an arm on the the shaft so it's
near the diameter you want to machine. Next weld on a carbide lathe
cutting tool to fine tune to the diameter you want to machine. A
square shank brazed carbide tool works well. If you need an accurate
diameter or several cuts you will have to remount the cutter each time or make
it adjustable to begin with. Turn the shaft with the drill to provide the
rotary cutting force. For the feed mechanism, use the hydraulic jack or
screw thread, or any means of feeding very slowly, to slide the shaft
through the the flange bearings allowing the tool to cut the surface you
need to bore.
It takes two people, one to operate the drill and
one to operate the feed system, but it works. It's also a great way to
line bore something where two distant bores need to be true to each other.
For that, you need a long shaft.
Of course there is room for improvements in
what I described. With some tinkering time you could make a
better and easier to adjust rig. It can't be built to light
because it may chatter. The chatter can also be controlled by
playing with cutter geometry and speed changes.
Crude but it works.
Dan H.
----- Original Message -----
Sent: Saturday, November 29, 2008 3:39
AM
Subject: RE: [PSUBS-MAILIST] how to
machine a big pipe end?
Alec,
There exist bolt on
machines for facing flanges or boring diameters on-site. Burt it is not so
common that every hire shop has them.
Or an old
shipbuilders trick; make a small, local area where is to much material red
hot. When cooling down that area shrinks permanent and can stretch a plate or
bend pipe.
All the best,
Emile
Van:
owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] Namens Smyth, Alec
Verzonden: vrijdag 28 november 2008
23:47
Aan:
personal_submersibles@psubs.org
Onderwerp: [PSUBS-MAILIST] how to machine
a big pipe end?
I have a typical
fabrication difficulty, and am wondering if anyone can recommend a tool or
idea.
The ends of my battery pods that
receive removable endcaps have a SS inside shoulder, and were buttered in SS.
The shoulder and SS were then machined to a close tolerance to seal with a
similar SS ring on the edge of the endcap. When this machining was
done, the pod pipe was only about 18" long so that it would fit on the
lathe. That short bit has now been welded to a much longer one, and I've also
welded on external stiffeners, through-hulls, etc. None of the welding was
less than 10" from the machined end, which I thought would prevent heat
distortion. One of the pods came out fine, but with the other I was wrong, the
pipe end is now an oval.
I've tried stretching the short
diameter of the oval with a 2 ton hydralulic jack. That corrected it
a bit, but I still have about 0.015" to go. This jack can't stretch the
pipe any further, it's reached its limit. But in any case, that's such an
inexact way of fixing the problem I don't think I could get it properly round
to the final few thousandths this way. I think I need to re-machine this
pipe-end in place, and obviously it isn't going to fit back on a lathe as
is.
- Cut the pipe again to put the
pipe end on the lathe, and re-weld.
- Make a jig that will center on
the pipe ID and have a longitudinal shaft, with an adjustable arm
mounted to it and a lathe cutting tool on the end of
that. Yuck, a lot of work.
- Is there some specialized tool out
there?
Any ideas are welcome! BTW the pipe is 12.75"
OD.
The contents of this
e-mail are intended for the named addressee only. It contains information that
may be confidential. Unless you are the named addressee or an authorized
designee, you may not copy or use it, or disclose it to anyone else. If you
received it in error please notify us immediately and then destroy
it.
No virus found in this incoming message.
Checked
by AVG - http://www.avg.com
Version: 8.0.176 / Virus Database:
270.9.11/1816 - Release Date: 27-11-2008
19:53
|