Hi horton. Thanks for your interest in making your own atty
coils.
When soldering nichrome wire, the nichrome doesn't want to take the solder nearly as easily as the copper or nickle plated wire. So, to promote a good connection there are a few things that need to be done.
I'll explain it as I "do it".
I consider a physical connection, "loop and hook", a must. If the heat softens the solder the physical connection will hold till it recools. Vaporization of most eliquids occurs at just over 400* and the solder listed below is rated for 420*. The soldered ends can see that temperature on certain occasions, but it's not "normal". So making a loop on the connecting wire and the nichrome wire end, then squeezing them closed pretty much insures if the solder softens the wire will not "pop" apart.
I have a dedicated tip for soldering atty coils. I consider this a must. They are cheap and just unscrew from the soldering iron, pencil or pistol. Once a tip has been used with solder that may contain Lead, or old equipment joints, you can never clean it well enough to be sure. So, we start with a new tip and use it just for attys. I remove mine and put it in with my atty materials when cool.
I put the new tip in a drill and sstroke a file against it till it has a long fine point, like a pencil. The factory 60* tip isn't the best for fine work, blocks your view and promotes big joints. The threads may dent a little from the drill, no worry as its soft copper and will thread right back in. Before removing the tip from the drill, I spin it with 320 then 400 grit emery paper to remove the scratches. This promotes longer tip life.
Next, tin the tip with a lead free silver bearing solder and wipe clean. Silver, even at 4%, helps with conductivity and has a higher melting temperature. I use Rat Shacks 64-026. They do have a finer diameter in some stores. If so, I prefer it or I split the .062 (1/16) dia solder down the middle.
Next consideration is heat range. It takes about 30 watts to get a good joint with nichrome wire. You will also need a flux other than "rosin core" when soldering nichrome wire. I personally use Ruby Soldering paste(local hardware store). It contains Zinc Chloride. It rinses away easily when done and promotes a good joint. Put it on the joint to be soldered 1st, heat the joint for about 2-3 sec, and touch the solder to the joint. The rosin core solder alone just doesn't "condition" the nichrome wire well for a good joint. Some use phosphoric acid based fluxes. They work well, but don't seem to rinse as easily. Basically, any flux used will need to be rinsed off before use. A good joint will take more than just rosin core though. The rosin care can be used with the other flux. It need not be rosin free.
Following those steps should give you a good well flowed joint. If not, the soldering tip may be oxidized on the threads. It can be loosened a few times and then re-tightened securely. The heat should return. The tip threads (copper) will oxidize from heating and cooling cycles. When the "scale" forms, the heat will be greatly reduced. A bad joint can be saved by just putting a small amount of flux on it and when the soldering iron is up to temperature, reheat it. If the tip is hot, but still to cool, the flux will just burn away before the joint melts.
That should put you the road for nichrome wire soldering!
