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Workshop Hints
Soldering Hints
The British Horological Institute has archived and edited the following from e-mails sent to the Clock/Clockers mailing lists on the Internet. The information here does not necessarily indicate a method approved by the BHI, we are only publishing this digest so that others can decide for themselves whether the methods listed below will suit them.
From:
Rick Gilmour, Jim Alexander, Murray R. Falk, Ron Morris, Mr.Kevin Eva, Richard Watkins, Richard Karasik, Alan Heldman, Alan Heugh, Dennis Kaye, Tom Kroos, Chuck Wilkie, J. M. 'Abe' Abernathy, Jr., PCS, Richard Karasik, steve ross, Bill Westbrook
Index
General Hints
Types of heat source
Low melting point solder
Removing excess solder
Anti-flux
Hints
Good soldering requires 1) a clean surfaces, 2) flux, 3) solder, 4) a proper heat source and 5) good timing. If the items to be soldered are not heated enough, the solder will not flow between them to produce a good bond.
- On joints where you absolutely must control the amount of solder, rather than feeding a stick of solder into the heated area, you can place a small piece of solder in the joint area, and heat gently from below or the side. The idea being to raise the temperature of the metals to be joined up to soldering point before the solder melts.
- Any of the many formulations of "soft" solder should bond to brass. (Of course the hard or silver solders do, too). Either of two things can go wrong:
- the brass surface is not freshly clean
- you're not getting enough heat to the parts.
- You should heat the bezel with a pointed flame (avoiding melting the other soldered areas) and touch the solder to the hot bezel. It should flow on rather than bead up.
- You can use any of the fluxes which hardware stores sell for use on copper water pipes. In elaborate soldering jobs it's almost a necessity to have solders with several different melting points, so that you can using the hardest-to-melt one on the first joint, then one with a lower melting point so that you can do the next joint without melting out the first one, etc.
- You might get the solder melting onto the small piece without flowing onto the larger; in that case first melt a bit onto the larger piece and then set the smaller part on the solder and re-melt it.
- Make sure you wash all the burnt flux off afterwards, otherwise the lot will be going green in no time
- I have only discoloured bezels when I had poor surface prep, no flux, and hence a poor joint.
- "wet" each surface independently with solder, i.e. heat it up and flow solder onto the surface without bonding the surface to anything. This will then guarantee that the next time you align and heat the bond will be perfect. If the wetting fails, you know you have more cleaning to do and don't have to worry about unwedging the two parts again. -its neater too because you can wick unwanted solder away from each surface independently and then have a very thin yet strong joint.
Soldering techniques
- After cleaning the area with steel wool or fine abrasive
- put on a dab of flux and a flattened piece of solder (just squish off a piece with your pliers) sandwiched between the bezel and the tab.
- Putting heat to it with a soldering gun, you will feel the solder melt and the tab attach to the bezel. heat for a few seconds more, then carefully remove the gun. Sometimes letting the gun cool for a short time will aid in removal without disturbing the solder bond.
- Clean any traces of extra flux thoroughly, so that it doesn't corrode the bezel later.
Types of heat source
Use an alcohol lamp, a small butane torch, a small pencil-tip torch for almost all applications, but when you really need a lot of heat, as for example, when silver-soldering or hard-soldering (which for me are the same thing), use a propane torch, with a pencil-flame tip.
Use the soldering gun except for soldering electrical wires etc.
Low Melting point solders
Even though it's more expensive than lead solder, it's as strong (or almost as strong) as silver solder, but at a lower melting point. The TIX products are excellent. While not terribly concerned about the hardness of the solder itself, because I know it is a SOFT-SOLDER, and I use it only as such, and not where a HARD solder should be used, the low melting-point is sometimes advantageous. For example,
- I recently used it to attach bits of hardened mainspring stock to the active faces of the anchor pallets of an old English bell-strike movement where a previous "repairer" had filed off so much of the pallets that neither pallet locked correctly. The TIX product enabled the repair without taking the hardness out of the steel, which would have happened if a higher melting point product had been used.
- Replace comb teeth on a music box the repair can not be seen and seems very strong. Its seems to be a perfect material for bezel repairs.
Removing excess solder
- Desoldering wick
The desoldering wick is a flattened, braided copper sheath looking for all the world like shielding on phono cord (except that the shielding is tinned) without the cord.
It works by capillary action, as you might suspect from its US name: "wick." I have used this stuff on electronic circuit boards with success, but there is always a problem holding the wick in intimate contact with the solder, heating until the wick has absorbed some solder, then removing wick plus solder. (Remember, if you remove the heat before you remove the wick-plus-solder, you have merely soldered the copper wicking to whatever you were trying to get the solder off of.)
Solder wick can also be used, it is basically a flux-impregnated copper braid that acts as a wick. It is heated by the soldering iron, and the molten solder flows up the braid by capillary action. I have had the best luck using the ones that have a good coating of rosin, and use the smallest size possible in relation to the work so you don't overheat the item you are desoldering.
For larger surfaces, use a 100 watt American Beauty electric soldering iron, and use fine steel wool 000 or 0000, and wipe off the solder when molten. - Solder suckers
"solder-suckers" are little rubber bulbs with nylon tips. Radio Shack sells them in the USA, but LaRose also sells them as air-blowers for blowing the dust off things. (The LaRose version looks the same in the picture, but I've never had one in my hand to compare with my Radio-Shack model.)
So...get a solder-sucker, and you have a dust-blower, too!
P.S. Not infrequently, the blob of solder you have just sucked off the substrate hardens in the tube of the solder-sucker. You must therefore have a wire of the right diameter (paper clip in my case) to push the blob out or in, after having removed the tip from the bulb.
Anti-Flux
In any soldering, some form of flux is necessary to cause the solder to flow into the cleaned joint. Anti flux is necessary if it is important to keep the solder out of some region closely adjacent. You just paint it on, for example, the joint of a hinge, when attaching it to a bezel with TIX solder (and rivets). It does as intended, keeping the solder out of where it is not supposed to go, and allowing proper heat on the parts where it is to go, so that the solder may flow properly. It also cleans up easily with a bit of water.
(I understand the anti-flux can be made at home with a bit of yellow ochre from an artists' supply shop, mixed to a cream-like consistency with half water and half alcohol and a bit of acetone, but have not tried this myself, because the bottle I bought a year or so ago is still not depleted.)
A useful *anti-flux* is ordinary toothpaste. Smells a bit, and the smoke from burnt peppermint may not be healthy.......but it works. A good lump of toothpaste can also be used, when no other method is available, to keep a small component cool while soldering is being done nearby.
