On 3/29/2018 10:24 AM, Jim Wilkins wrote:
> I just signed up for a blacksmithing class. The instructor isn't
> averse to non-traditional methods and has MIG and acetylene in the
> shop. What should I watch out for if I plan to hot forge a previously
> arc welded joint? I could be welding high and low carbon steels
Most likely you would be welding for the purpose of making forge welding
go easier. The number one biggest thing is to get dirt, oil, mill
scale, and rust off the pieces before you start. You want clean steel
on steel surfaces, and then you would use flux to reduce oxidation, but
there are guys who claim with a properly setup forge with a reducing
flame you don't need flux. Even for multi layer hammer forged damascus.
Acetylene can be used for "Spot" heat treating where you can harden one
area of a part while leaving the rest soft(er).
I am sure there is a lot more. I'm just an armchair blacksmith. LOL.
Normally, you would never plan to forge an arc welded join, at least
not more than just enough to slightly adjust a fit or match to a
An exception is tacking pieces together prior to forge welding. If
I don't have a helper and the join is awkward, I might tack two
pieces together with small torch or MIG welds, as little as possible.
In the case of Damascus (properly, pattern-welded) billets tacked at
the ends, you'd normally cut off the weld material before you're done,
not fold it into the finished piece.
Depending on the workpiece and what finish you mean to use, differing
materials -- base and weld filler -- might well show up unsuitably in
the finished piece. In any case, arc/gas wellding tempts you to take
an easy way out rather than figureout a way to exploit the medium.
The central mystique of blacksmithing is that iron is soft, malleable,
mushy, plastic in the smith's hands. As a learner, you should
concentrate on that, abandoning any existing perspective acquired from
welding in the fab shop.
That said, I'm not a purist. When assembling complex pieces that
themselves are expressive of the plasticity of hot iron, arc welding
can make a piece that would be impossible (or nearly so) work well
without intruding the different aesthetic of arc welding on the
aesthetic of a piece. Here's an example:
The legs and claws are attached to the carapace with arc welding,
completely concealed by the snap-on plastron.
on the other hand, has numerous joins with arc and gas welding. All
those welds were carefully ground, filed and hammered to keep them
from distracting from the overall forged nature of the piece. In this
case there was no other way to get to the desired end.
Oh, and I've been smithing for about 50 years.
Your artistry is magnificent, mine non-existent.
For me this is another means to shape functional machine and tool
components that are too large, flexible or irregular to clamp in a
milling machine. I'm like a get-it-running-again millwright, or a
farmer patching a broken hay rake tine. One of my projects will be
crucible tongs and I'm considering arc welding to fabricate a box
joint for the pivot. I'm the only customer and I don't care what it
looks like, as long as it -works-.
When I built prototypes to pass around at board meetings I was careful
of the appearance but I'd never be mistaken for an industrial
Never too late to acquire some. In 1980, I was talking to some older
smiths in England who were opining that you had to start at 14 if you
were ever going to be a *real* blacksmith. Welllll, maybe 16 would be
okay. We turned to one of the official demonstrators at the event and
asked when he'd started. "When I was 40", he replied.
Ah, me too. I see that I lied by omission. I'm kinda envious of the
smiths who make tools and fixtures that are themselves works of art.
But I never have the patience because I want the tool *now* so that
the thing the tool makes will appear magically.
So I have a lot of nicely made *old* tools but when I need a jig or
fixture or special pair of tongs, forging and arc welding go hand in
hand with welding often taking the lead. I have some pretty ugly,
dribbly jigs that work very nicely, cobbled up out of offcuts, other
tools (such as a valve spring compressor) and custom-forged parts.
Tine for my tiller or rosebud hinges for my woodshed? All forged.
Guillotine fuller (aka "smithin' magician") or flat-die insert for the
power hammer? Band saw, drill press, torch and arc welder.
I don't know when he started but my grandfather shoe'd his first horse
at 8, but he would have been around 30 when he converted the Ford 999
from tiller steering to a two handled bicycle grip to suite Barney
That's the idea. I want to learn to avoid mistakes that would
compromise the strength of a welded and then forged joint, the way I
practiced welding butt and tee joints with 7018 rod until the weld
would withstand being bent double on the school shop's 50 ton press. I
think that means using a sufficiently ductile and malleable rod
(which?), rather than choosing it only for tensile strength.
Th application would most likely be building up a weak spot that
reveals itself in use and then hot and cold forging it to smooth,
stress-relieve, compact and hopefully work harden the metal. For
instance I forged a tong joint thinner than I should have.
Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here.
All logos and trade names are the property of their respective owners.