Hi Dan, I checked out your suggestion of tube bending using
bismuth from smallparts. It sounds interesting! I thought I'd try
using the 158F melting temperature alloy with sterling. Any
thoughts on this choice?
John, Seems like a good midway choice. I imagine it would boil out
quicker. I chose the 255 alloy due to it’s higher Brinell Hardness
of 10.2 and is cadium free, but it does contain lead. I figured the
higher hardness would give me smoother shaping and reduce the risk
of denting when forming it around something. I took the extra step
of using a gun barrel cleaning pad to swipe it clean while warm
before hard soldering. I haven’t tried any of the others alloys.
Here’ s a useful chart, although I doubt you won’t need it, unless
you live in the Himalayas, “Boiling Point of Water at Various
Altitudes and Pressures” at this site:
To plug the end before filling the tube, I used pith-wood, which is
commonly use by watchmakers. A swab of cotton will work. The
important thing is to let the air flow out the opposite end as you
fill it. I used a makeshift paper funnel. I melted the alloy in a
pyrex container with an alcohol lamp. Pouring the exact amount is
tricky, so I just let the excess metal solidify to form a ‘casting
button’ in the funnel. Be sure to rehearse.
Let me know how it turns out.
Daniel Biery Jr.