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5th March 1971, Page 38
5th March 1971
Page 38
Page 38, 5th March 1971 — road and workshop
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Which of the following most accurately describes the problem?

Benchwise: can you solder?

by Handyman

IN MY EXPERIENCE less use is made of the soldering iron in transport workshops today than used to be the case. Consequently, there is less scope for the younger mechanic to practise this skill. Yet there are still many occasions when use of soft solder is the best answer to problems which he may face—from tinning heavy battery or starter terminals to prevent early corrosion, to repairing control cables, heater radiators, petrol (but not, of course, diesel engine) pipes, tinning other items against corrosion, and levelling dents in steel panels. And this is to name only a few.

I accept that the use of glass reinforced plastics and various levelling pastes can make for a quick, simple job, but none can beat solder for long life and standing up to rough usage. Unfortunately, there are too few people around. now who can really handle the soldering iron or successfully lay on solder with flame, so I feel sure a few words on the subject will not come amiss.

Technique needed

When watching the expert tin his iron and place the solder quickly and neatly just where it is required, the process may appear simple and straightforward, yet some considerable practice and a sound knowledge of the technique are required. Soft solders are based upon tin and lead, and range from almost pure tin to pure lead, according to the purpose required. A point which causes confusion is that pure lead will melt at 327deg C and pure tin at 332deg C yet a solder composed of equal parts of lead and tin will melt at just over 200deg C and will solidify at around 183deg C—a very useful property indeed.

Absolute cleanliness is essential in soldering; all too often when a mechanic fails to make things stick after having cleaned the parts well enough, he has forgotten the fine coating of oil or grease on his hands which is so easily transferred to the job. Therefore, point one: cleanse and dry hands thoroughly, then deal with each part to be soldered. Not only must the parts be bright and cleaned of any oil or grease but also free of paint, oxide, etc.

Point two: remember also that a stick of solder picked out of a bench drawer or a tool box may not look dirty but is affected and should be buffed clean before use. In addition to the buffing and cleaning, the areas to be joined or tinned must be protected from oxidation during soldering, and a flux is required to dissolve any oxide, and not to clean the surfaces, as so many people think. Today, it is not the practice of the workman to make up his own flux as in earlier years, instead there are several reliable proprietary brands available, and while they all give good results they may be slightly corrosive so it is essential to wash the finished work with hot water to remove the flux.

Solder grades

For general garage work, a grade B solder is most suitable with a soldering iron; this solder is roughly half tin and half lead. For electrical work use grade E which is 95 per cent tin.

The largest possible iron should be used and be cleaned bright and tinned in a clean receptacle; this will also assist in obtaining the correct heat in the iron, ie just enough to cause the solder to flow cleanly and easily. A cooling iron will only create a pasty substance that is useless; just too much heat will drive the solder away in a globule, or make it brittle. So practice is needed until familiar with the required heat.

The parts to be joined must first be cleaned and immediately afterwards tinned, with a touch of flux, a little solder Melted on and flowing freely, then wiped quickly, leaving a thin film of solder over the full areas. After this they can be pressed together, using the hot iron or flame to bring about full adhesion by fusing the tinned surfaces.

Where additional solder is needed to fill or build up the work, keep the tip of the iron clean by an occasional wipe with a cloth, warm the work and let the solder flow into the work freely—this will fill any crevices clear of blow holes.

A number of tips should prove valuable to the trainee. For instance, if a large area of plate is to be dealt with, and only a portion of it is to receive solder, it is essential that the heat is uniform throughout the plate otherwise the heat will at once soak away into the colder areas.

The same point applies where soldering copper or brass pipes—do not grip these in the vice close to the soldering area, otherwise the heat will be lost into the steel vice. In fact, the heat may be lost quicker than gained and the area near the flame can burn and collapse, or the solder will roll into balls and fail to adhere.

A good practice with any form of piping is to lay it out on fire bricks that will give insulation—and support where needed.

Remember, too, that even a long copper pipe will not be as cool as it may appear during and after a heating and soldering job.

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