RE: having trouble soldering
[8D] Don't lose faith. Credentials: 20 years in eletronics and amateur radio.
I would never, ever file a soldering iron tip. They should come properly shaped, tinned and ready to work. Some tips will have a colored coating on them, often this is blue. This has to come off. You can usually get it off just by heating and take an rag and clean it off.
When the solder just boils off the tip, the tip needs to be cleaned. Always have a damp sponge to wipe the tip of your iron. You should wipe the tip literally every time you pick it up to make a solder joint. The tip rapidly oxidizes due to the heat. This prevents efficient heat transfer to the joint. After wiping the tip on the sponge, touch a little solder to the tip. It only takes a little. Touch the tip to the joint. Let the joint heat for a few seconds and touch the solder to the joint, not the soldering tip this time. If the solder melts, then you are ready to go. Add solder and let it wick into the joint. Only add solder until the joint is silver with solder. then remove the solder and the tip. Do not move any components of the joint. If you are soldering terminals, it mayy take several seconds for the joint to cool. If you move anything with the joint, it will weaken the connections. If the solder is not shiny silver and and is a dull gray, you need to re-heat it. Cold joint will fail and they are subject to intermitent problems from what is called "cold" joints.
Terminals are especially problemmatic. The take a lot of heat and you usually have to hold them with something. Pliers and vices that are metal will make it take even more heat. This is the thermal conductivity transferring the heat you want to the pliers or vice. Try usind wood to hold the connector. You can drill a hole in a piece of wood for round connectors. You can also use a dowel rod or place the connector in a vise and use two pieces of wood to insulate the jaws. If you have a vise with non-metallic jaws, be be sure they won't melt at about 750 degrees. Your soldering iron needs to heat the joint to this temperature to melt most common solders.
Flux helps the joint take heat. A little flux can also help you tin the tip. Most electronic solders are rosin core or ersin core or some other core. The core is flux. These solders to not need addtional flux most of the time. The solid core solder will need flux to work well. As someone else posted, NEVER use acid flux in electronic circuits.
Now, if you are soldering to large terminals, it is helpful to "tin" the connector and the wires before attempting to join them. Tinning is just heating the wire or terminal and melting some solder on it. Again, you have to melt the solder on the wire or the terminal, not the soldering iron. Sometimes if you cannot seem to get the solder to melt, wipe the tip with the wet sponge again, tin the tip my melting solder on it, then heat the wire or connector and try to get the solder to melt on it. After you tin both of the surfaces you need to join, then just heat the connector until you see the solder re-melt then continue to heat the connector and insert the wire. Look for the solder to flow then remove the heat.
The thickness of the solder can also be a problem. If you bought solder at Lowe's for soldering copper pipes, it is large, solid core solder. This is hard to melt. You want a 60/40 (60% tin and 40%l ead) solder for electronics that is small diameter about .03 inch. You can get it at Radio Shack. Lowe's and Home Depot may have it to but it won't be in the plumbing aisle.
The really big guns are for large metal surfaces. Coax connectors or soldering wires to a chassis need the big heaters. You should not need one for RC modeling.
[sm=regular_smile.gif] Now for the big soldering tip. You may have a heat gun for working with coverings. You can also use it to solder. I am talking about a heat gun, not a hair dryer. Heat guns often readh 1000 degrees. If you need to unsolder something you can heat it with a heat gun and then remove the wire from the connection. I also recently used this technique to solder some large terminals. Some heat guns come with a couple of deflectors to "shape" the flow of hot air. A small circle one will help you use this technique without adding too much heat to surrounding surfaces. This is great for salvaging electronic components from old boards or broken equipment.
I hope this helps.
Wayne