OldTools Archive

Recent Bios FAQ

263029 Erik Levin 2017‑08‑20 Re: Assembling a plane - Norris vs Spiers
Bill Webber wrote: "On the one hand, I'm certain the metal for the sole of his
kits is malleable enough to fill around the filed dovetails.  One the other 
hand, I think making the triangular divot in the sole is easier to do 
but then I need more information on how malleable his provided brass 
might be.  The idea of annealing it doesn't appeal as I don't have the 
the required torch or experience." and Thomas Conroy responded: 
> Probably that you have far more experience working brass than I do, but 
> for what it is worth I offer my impression that all copper alloys workharden 
> abnormally quickly. Like: one blow of the hammer and it moves and spreads as 
> sweet as you please, just as you want it to. Two blows of the hammer, it moves
a
> scutch more, not much.

It really depends on the alloy. I have bronze punches that are as hard as good
tool steels, and I have bronze punches that have been rearranging themselves in
a ductile manner for years, to the point where one is about half as long as it
started and a lot fatter, though some of this is the mushrooming at the ends. I
have done a fair bit of forming, welding, and forging of steels and red metals,
and learned early that you really need to know the particulars of the alloy (and
learned that much of what I learned in school an the field is incomplete or
misleading)

Most copper alloys are annealed by heat and rapid quench-- the opposite of
steels. The (simplified) explanation I have seen in a number of books and
learned in college is that the ductility is enhanced by trapping dislocations in
these metals. (the details depend, in part, on the underlying crystal structure
for many useful properties. For example, many aluminum alloys have low ductile-
to-brittle transition as temperature goes down, as they don't change phase t a
brittle structure like steels tend to.) It is really more complex, but I am not
a materials scientist, so I will leave it there.

For practical purposes with pure copper (such as making gaskets for high
pressure steam systems from deoxidized electrolytic copper rod up to about 6mm
diameter), quenching isn't generally needed for thing sections, as air cooling
is rapid enough to achieve dead soft condition.

For annealing smaller work in lighter material, like one might use for a plane,
annealing isn't a big deal. A plumbers torch (propane or air-acetylene) with a
heating tip (broad flame or rosebud, not pointed flame) will provide sufficient
heat. I have annealed copper for making gaskets using a BBQ,  gas cooktop, and
electric cooktop, as well. You don't need melting heat. For many red metals, the
ballpark of  550C (1000F) is what you want, with a water quench. Pure copper
might need to go to 600C or a bit more. Some alloys a bit higher yet. Some
alloys will lose the primary alloy element (tin or zinc) at the surface when
annealing, leaving a copper skin, with the usual oxides if not protected. This
is removed, with the oxides, by appropriate pickling.


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Recent Bios FAQ