Blueskies wrote:
"Ernest Christley" wrote in message ...
: J.Kahn wrote:
: Blueskies wrote:
: I am a rookie at this welding stuff, and plan to get plenty of
: practice before building real airplane parts. That said, what do you
: all think about heat treating after welding? I will be gas welding. Do
: I really need 4130 rod, or can I use another high carbon steel rod?
: How about 'S2' rod (only if not heat treating?)?
:
: I have seen all sorts of discussion about this, but none of it is
: really clear. I know some of you folks are indeed experts so I am
: seeking your advise.
:
: Thanks All!
:
: Dan D.
: Kalamazoo, MI
:
:
: Do not use 4130 rod, which would require oven heat treatment of the
: welds. RG45 mild steel rod is best for gas welding. Also don't use ER
: rod, which is also mild steel but which is formulated for arc and works
: poorly with gas.
:
: Mild steel rod provides perfectly adequate joints because the weld
: fillet is several times thicker than the parent metal, while at the same
: time being softer material it provides better fatigue resistance.
:
: When doing finish welding of clusters, as the last weld of a cluster is
: complete and while the cluster area is still hot, go back over the
: cluster to bring the entire cluster up to dull red (not orange) then let
: it air cool with no drafts. This brings the zone reasonably close to
: the original normalized state of the parent metal and is all that is
: necessary.
:
: The secret to not burning through on thin tube at the start is to get
: the parent metal just under the melting point and drop a molten bead of
: rod on the joint, then heat the bead until the adjacent metal melts and
: the bead blends into the parent metal. Then start adding more rod and
: moving the torch.
:
: The rod plays a role in heat control. When an edge starts to burn away
: back off just slightly and put the rod in the way of the flame which
: limits the heat to the burnout and deposits rod there to fill it in at
: the same time, then keep going. This is the way to deal with burnaways
: without getting all flustered and stopping.
:
: Be generous with rod feed to the puddle to keep it "full" as you advance
: to avoid undercut edges. If you get the puddle nice and full looking
: and feathered into the parent material all round the edge, then just
: move the torch along while keeping the puddle full with rod, you will
: get a beautiful textbook bead that looks almost like a TIG bead with
: full penetration.
:
: Gas is great because it is very forgiving of imperfect technique and you
: can go back over mistakes if necessary.
:
:
: John
:
: Everything he said, with one addition. Practice on strips of thin sheet
: stood on edge. You should be able to move down the edge, making a
: rounded off fat bead that sort of sits as a bubble on tops. You should
: pratice moving the torch in and out, getting the metal to melt but not
: flow, and holding it there. Once you can do that, the thin walled tube
: will be much easier.


Thanks all! I have been practicing melting metal this week. Pretty amazing 'art', this welding. My blobs are not very
pretty (downright ugly in fact), and just getting the torch right is part of the battle. Great fun!

I don't have a bunch of thin scrap to work on, but I do have some old 1/8" iron that I am playing with, and then going
back to the 4130 scraps and blowing holes through it. I see Spruce has a grab bag of shorts that I will probably buy,
and I need about 1' of 3" wide 0.065" 4130, so I am planning to buy some strips from them also.

Side note, any hints on cutting the strip?

Thanks again!

Dan D. in Kalamazoo MI



Dunno what torch you're using Dan, but I can highly recommend the Meco
Midget with a 0, 1, 2 and 3 tip, plus a 0 tip drilled to halfway between
0 and 1 (# 74 wire drill). The 0 for .028, the 0.5 for .035, the 1 for
..035 in dense areas and sometimes .049, and the 2 for .049, and the 3
and possibly a #4 for .065. The "Tinman", Kent White, sells the Meco
for a fantastic price and has a really good and quite comprehensive DVD
on building a tube fuselage done with Earl Luce the Buttercup Guy and
Joe Maj, an Oshkosh welding guru and a chemistry PhD.

The Midget is actually a jeweler's torch, but in the big end of the
range as jeweler's torches go and is perfect for thinwall tube since it
is feather light and you can hold it in your hand like a pen. When you
get the tip size and gas flow right for the job it doesn't pop. I
absolutely love mine.

The other torch I really like is the Henrob but it is really heavy and
a bit awkward in tight spaces. The Henrob does great flame cuts but
this is a no no on aircraft metal because the flame cut edge is heavily
oxidized.

If you are perceptive and learn what to look for you can acquire most of
the skill to do good welds by practicing on your own with the help of
reading materials and videos. When you are to the point in the future
where you think your welds are airworthy, cut up some cross section
samples and take them to a certified welder for some critique.

John