Bending tubing

It may be difficult to separate "theory" from "application," but let''s see if this helps facilitate the discussion.
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Richard Hull
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Bending tubing

Post by Richard Hull »

One of the easiest ways to bend tubing is to use a low melting point alloy to fill the tubing. The tubing is then readily bent and just a mild warming of the tubing will re-liquify the metal which can then be blown out of even the finest ss capilary tubing with air pressure. Naturally, on large diameter tubing it can just simply be poured out and re-used over and over.

Among the many alloys are Woods metal, Lipowitz metal, etc. alloys from 117 deg F to nearly 200 deg F can be used with little heat applied and low to zero risk of severe burns.

I have used this technique on several occasions.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Bending tubing

Post by guest »

I completely forgot about this discussion posted on this board or the old fusor board. Does woods metal or Lipowitz metal leave any residue? And is safe to work without hazmat gear? (i.e. no Mercury, Cadium, etc.) If I remember correctly, woods metal is used on sprinker heads and is an alloy of tin.
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Richard Hull
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Re: Bending tubing

Post by Richard Hull »

It just so happens LMPA (Low Melting Point Alloys) is a specialty of mine. I make up my own from base metals. All alloys melting below 200 degrees F are quantinary or quintinary alloys. All contain Cadmium, but in low percentage, (<5%). If one is not a knee jerk greenpeacer and reads up on the vapor pressure of cadmium at the alloy's melting point there is zero danger.

The metal leaves no residue in SS provided you are not using the all wetting indium alloy which melts at 117 degrees. So Woods, Lipowitz or their modifications can be used with impunity and no fear in the 158 degree F range. As they are composed of Lead, Tin, Bismuth, and Cadmium, they may wet copper, nickel, or other metals to a limited degree. However, the alloy is brittle and crystaline and will detach easily from even copper if tapped. It is often suggested that a wax tallow coat the inside of the tubing prior to casting. This can help avoid wetting of the tubing even when using Indium alloys.

These alloys are also used by lens grinders and pattern makers and machinists to hold work fast to a table of chuck for working. Once done, a blow dryer will release the item and the metal recovered and recast to bar or ingot for future use.

I have a couple of different LPMAs on hand and offer it for sale in the trading post forum on this list.

GREAT STUFF.

P.S. A word of warning. DO NOT make your own metal. Cadmium must be initially inroduced to a rather hot mix near the fatal vapor pressure point around 600 degrees F. You would need a fume hood and a special OSHA respirator with filter specified for cadmium vapors to avoid those nasty near death experiences. I have this stuff and use it religiously.

The finished alloy need never be, and should never be heated above 180 degrees F where the minimalist cadmium locked in the alloy is totally safe in normal use. Never melt an LMPA with a torch or flame especially not directed at the metal itself. Indirectly heat the metal in an electrically controlled, calibrated solder pot or frypan or whatever you have of that ilk.

If you heat the stuff above 700 degrees by accident...you will see the nasty red-orange cadmium fumes and will also be accidentally killed. Perhaps deservedly so. Remember, as a physics investigator/experimenter there are more ways to be killed that be successful. It is up to you to know a bit about materials science, electrical science, engineering issues and common safety and health hazards and how mixing them might create new unforeseen interactions. Like a magnesium or zirconium fire. A CO2 extinguisher or water will cause it to flare up as the CO2 or H20 is immediately separated and the oxygen used to feed the fire. Only sand works, but ya' gotta' know this prior to working with the stuff.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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