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How To Solder:


Okay. You say. I like working on my cars and can do most things, but I just can not solder. Every time I try, I make a bloody mess of it. Well you are probably right, most people have problems soldering. It is not magic, just a lack of understanding what you are trying to do. It is a skill to be learned and practice will make it near perfect. There two basic principles to soldering.

....No.1 The work pieces to be soldered must be mechanically and chemically CLEAN.
....No.2 There must be sufficient HEAT applied to successfully complete the operation.

Clean mechanically means that the joint to be soldered has been prepared to fit properly, either by placement or filing etc. to make the pieces fit. Improper fitting components makes it hard to get a good joint. If it is a previously soldered joint that broke, the old solder must be removed to refit the joint. It also means that any corrosion, dirt, grease or rust be removed. The joint must also be chemically cleaned as well as physically prepped, This means the use of a flux or acid applied to the joint components. Usually when soldering brass components a good sanding to bright metal and a mild paste type flux is all you need. When steel is the material it must be sanded or filed and then it takes an acid in liquid form to clean or etch the steel well enough chemically.

The Flux cleans the materials chemically and then allows the solder when heated properly to flow into and around the joint for maximum strength, The solder must flow quite freely. Just blobbing it on will not do. There must be a chemical, mechanical and heat bonding of the solder and the joint components.

That brings us to the heat part of the job. Get a good soldering iron. It must provide at least 60 watts so a small tip electronics soldering iron will never get those larger joints done. I have for 34 years used a Weller 100/140 watt soldering gun. It has plenty heat to get the job done. They also make a larger version but I find it too clumsy to handle. There are also some newer soldering pencil type irons out there of sufficient wattage that stay hot all the time and sit in a holder. Which ever type you have, or get, keep the tips tight and clean before using make sure the tips are tinned well with flux and solder and wiped off with a rag to make them nice and shiny. Keep a damp sponge or rag handy to wipe the hot tip off every so often from the build up of flux and oxidation. If not they will limit the heat available for a good joint. A good joint will have a smooth shiny look and solder will have flowed enough to give a filleted look.

The solder used must be a good grade I prefer at least a 60/40 composition. That's sixty percent lead and forty percent tin. The best solder will have a rosin flux core. Which will do nicely for most jobs. If you use acid core keep it away from your motors and any wiring as it will eat them up with corrosion as well as rust any steel parts of your chassis or what ever. If you must use acid flux on steel components after soldering rinse the whole job off with hot water, and then dry and relube any bearings or bare metal areas.

I know the environmental wackos have restricted the sale of lead based solder and that remains your decision what to use but I have not found the new lead free solders to be worth a damn as far as making a good strong joint. You can still search out and find the good stuff. Many of the large electronic supply houses keep it on hand for their big companies that need it for good work.

Following these tips will mean you have a much better chance of doing a good job. Practice will make you much better at it. Many will tell you that to do it right you must apply the heat to the joint with the gun and then add the solder to the joint. That is good practice but not always possible. It is more important to have the joint held in position so it can not move, this will involve at least one hand to hold it. I heat my soldering iron up and apply the solder to the tip in sufficient quantity until it forms a small molten drop, then carefully apply the tip to the joint and let the solder flow off into the joint and make sure to keep the heat there till the solder does flow as it should. If you need more to complete the joint redo the same procedure and reheat the joint till the new solder flows into the whole joint and fills any gaps. I hope these ideas will help you out and that your solder jobs become something you can be proud of.

Larry Shephard

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