[python] Re: Welding or brazing?
- From: George Durbridge <gdurbrid@xxxxxxxxxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Wed, 01 Jun 2011 22:30:29 +1000
On Tue, 2011-05-31 at 23:17 -0700, Vi Vuong wrote:
> Hi Arjen,
>
>
> For relatively safe welding at home/outdoor, I suggest an inexpensive
> 110v flux-core welder (no gas needed). Buy high quality wire to
> minimize splatter, and go easy on the trigger at lowest setting for
> tubings. Do spot welding if needed to control the heat on very thin
> tube.
>
>
> If you have access to a shop with other methods, try them all which
> should be strong enough for tubings, but differ in control, heat,
> beads, and safety hazards. Here are some claims by Greenspeed:
> The frame tubes are MIG welded. MIG beads are not as fine as TIG,
> though the craftsmanship of the Greenspeed is exceptional. We don't
> see many MIG welded recumbents, so we asked Ian about it, "We find
> that MIG welding puts less heat into the tubing than TIG, and a lot
> less than brazing, leading to less of the metal around the joint
> losing its strength. We have also had superior performance from the
> MIG joints over brazed joints. In addition, we find that the MIG is
> quicker than TIG, and much faster than brazing, thus is is much better
> suited for production work".
> http://www.greenspeed.com.au/rdtest1.html
Ian Sims knows what he is talking about, but Greenspeed use MIG welding
with gas, not the gasless flux-core system. He is also referring to a
production line, not one-offs. Working on a one-off, you spend so much
more time preparing the pieces than welding them that the extra speed of
MIG hardly matters. Greenspeed's welders are very experienced and
competent and their welds are reliable, but for occasional welders it is
too easy to make "dry joints" using MIG, which spits metal spaghetti
over the joint, whether or not it melts the parent metal. The payoff for
the extra heat put into the workpiece with TIG is that you always know
you have melted the parent metal, as well as the rod. Ian may be wrong
on one point: most people think that brazing does not heat chromoly
enough to affect its strength. Although a larger area is heated, it is
heated to red heat, well below the melting point.
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