Looks like a cheap set of springs including 1/8"… no guarantees of quality, usual disclaimer etc..!

**LINK**

No idea where I got fields metal from- absolutely right, I meant Woods metal (and changed original post)… I bought a small ingot of woods metal but then found the uni workshop had springs I could borrow and never tried it… I think there are different flavours of woods metal with compositions including or not cadmium etc which may effect melting point and availability..?

Fields metal is a non toxic alternative to Woods metal as it contains no Lead or Cadmium.

Hello Paul,

Generally it's best to start with a longer length of pipe than you need, make the bend, and then cut the pipe back to where you want your nipple to be. If the nipple is already soldered onto the pipe then the job is more difficult because you have less leverage for bending.

Assuming this is copper, the way I normally do it is to make a simple slotted mandrel from a piece of scrap brass rod. Chuck a length of rod in the lathe and machine a slot a tiny bit wider than the pipe diameter and to a depth of at least 3/32" but preferably 1/8" deep. The width of the slot should be such that your pipe slips in and out of the slot easily but doesn't waggle around. The root diameter at the bottom of the slot should be your bend's desired inside radius. If in doubt, err on the side of a slightly smaller root diameter.

Anneal the pipe where you want the bend to be, put it into the slot, and gently push with your fingers to start the bend. As soon as the pipe begins to work harden (stiffen) gently ease it out of the mandrel and re-anneal. Repeat until the bend is finished to your satisfaction.

The above works because a pipe can only flatten in one direction if it can simultaneously stretch in another. The side walls of the slot prevent the pipe from widening and hence prevent the pipe from flattening. The pipe will tend to want to stick in the slot, especially if you bend too much between annealings, so beware. An improvement on the above is to make a two-piece mandrel where one half screws into the other to leave the 1/8" slot between. You can then partly unscrew one side of the mandrel to remove the pipe after each bend, overcoming the potential problem of the pipe jamming in the slot and being difficult to remove after bending.

Good luck,

Steve Goodbody

Edited By stephen goodbody on 28/02/2017 21:01:18