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Build your ownresistancesoldererGreat results forminimal investmentVance Bass, Albuquerque, NMIf you're like me, you don'tsolder things unless youabsolutely have to. The littlehassles add up: plug in the iron,wait (and wait!) for it to heatup, wait some more while yourwork piece warms up. Watchout for the hot iron while you'rereadying the next joint! Andwhen you're done, wait somemore for the iron to cool down.It’s too much work for a smalljob, so I put it off until there'sno avoiding it. But there's abetter way, both for small jobsand for more complex ones.I'm going to show you how toget over your resistance tosoldering, by building your ownresistance soldering unit.What is a resistancesolderer?It's very similar to the familiarsoldering pencil or gun, in thatit uses a resistive metal toconvert electricity into heat,permitting you to apply the heatat a specific point. It differsfrom the conventional solderinggun in that the piece to besoldered provides much of theelectrical resistance. Thus, youare heating the work internally,insuring that the metal is thePhoto 1 With a resistance solderer, you can solder thehinges on this tender hatch without undoing all the otherjoints.right temperature to make astrong solder joint.Additionally, since the heat isdeveloped only where you wantto solder, you don't have toworry about wasting timeheating a larger area, andperhaps having some of yourprevious efforts come loosefrom the spread of the heat.A resistance solderer differs, aswell, in that the heating of thematerial is practicallyinstantaneous. You step on thefoot switch and the work pieceis heated to workingtemperature in a second or two.When you release the switch,the resistance solderer's tip iscool to the touch. Only a smallportion of the piece yousoldered got hot, so it coolsmore quickly, too. (Photo 1.)This removes almost all of theobstacles of conventionalsoldering for me. No waitingfor the iron to heat up, nowaiting for the work to take theheat, no worries about burningmy shirt sleeve or theworkbench top, no waiting forthe iron to cool. And of course,you're wasting less electricityon all that unused andunproductive heat.What’s the cost?If you have read this far, I haveprobably addressed some ofyour irritations withconventional soldering irons.And now you're wondering,"Where do I get one of thesewonderful things, and what's itgoing to cost me?" You havetwo choices: buy or build. Youcan buy excellent units fromPBL, MicroMark and otherwell-known hobby suppliers.They are fairly expensive(typically around 250-300),but they are of very high qualityand will last a lifetime -- aworthwhile investmentaccording to those who oneone.Or, you can build your own fora fraction of the cost. It doesn't

showing a unitThe power source for yourconstructed from asolderer will be an automobilepowerbattery charger. Most chargerstransformer, aproduce 12 volts of directwooden dowelcurrent (12VDC) and between 2and a cheap D-celland 20 amps (2-20A). Mostbattery. It was notpeople who have built onea constructionrecommend 5A as a minimum.project for theIf you want to compare thisfaint-hearted,with your conventionalhowever. Cleversoldering iron, you canminds came upcalculate the wattage bywith a safe andmultiplying the voltage timesPhoto 2. The solderer is made from commerciallysimple alternative,the amperage: a 12VDC, 5Aavailable tools, modified to work together.though, and theunit consumes 60W. That isresistance solderernot to say that it produces thelook as polished, perhaps, and itis now an item every workshopsame heat as a 60W solderinghasn't gone through a nationalcan (and should) have.iron, however. Since the heat iselectrical safety inspector, but itgenerated right at the spot youwill do the same job. (YourTo simplify the construction,want to solder, you will betrackwork uses the samewe're going to usevoltages and amperages, by thecommercially availableway, so don't worry too muchproducts, and modifyabout the safety inspection.them somewhat so theyUse the common electricalcan be combined toprecautions and you should beform a resistancefine.) With this simple homesolderer. The bill ofmade solderer, you can soldermaterials lists the itemswiring joints or attach brassyou will need to build adetail parts in seconds. A unitPhoto 3. The footswitch controls the currentbasic unit. (Seelike this will not be suitable forflow from the transformer to the electrode.sidebar.) You cansoldering really large piecessubstitute equivalentradiating less of it into the airlike 1:20 scale brass locomotiveparts wherever you wish. (Thatand thus you will be using lesscabs or boilers, however. Forold Lionel ZW transformer inwattage to do the same job. Onthat, you'll still need to use ayour attic would make a goodsmall parts, you have to be fasttorch. But it will replace yourpower source, for example.)with the on/off switch, even atsoldering iron for most jobs,Construction should take only a2A, or you’ll heat your part redand will let you do many thingscouple of hours once you havehot!impossible to do with an iron.the materials.Construction madesimple.Hobbyists have circulated plansfor building resistance solderersfor years, and Narrow Gaugeand Short Line Gazettepublished an article in 1981The resistance solderer I’lldescribe consists of three mainpieces: the power source, thefootswitch , and the electrode.(Photo 2.) You may also add avoltage controller if you wish,made from a household lightdimmer switch.A foot switch permits you tocontrol the flow of electricityfrom the power source to theelectrode. The box housing thefootswitch has 1/4 inch jacks,into which the cords from thepower source and the electrodeare plugged. These are standard

musical cord jacks and plugs.(Photo 3.)The electrode consists of abakelite handle holding acarbon rod. (This could also bemade of wood or anotherinsulating material.) A heavycord connects the electrode tothe footswitch. One wire of thecord is attached to the carbonrod, while the other wire hangsloose, with an alligator clipattached to the end. You don’treally need a box of 50 cuttingtorch rods (I still have 49 in thebox). Try to find some friendsto share a box, or ask thewelding supply to sell you oneor two. If you have to buy theentire box, though, rememberthat you’re still saving a lot bybuilding it yourself.(Photo 4.)Cut the plug off the cord.Separate the wires on one endof the cord for about 6 inches,then strip both wires about 1/4inch. Strip the wires on theother end and solder them intothe other guitar plug. With apower hand drill, drill a 1/8inch hole about 1/2 inch fromthe bottom end of the handle,then gently move the drill uptowards the top end of thehandle, giving the hole an angleof about 45 degrees. This willsimplify moving the groundwire through it later. With ametal saw (hobby or hacksaw),cut the metal mounting barrel toleave about 1 inch above thebase. Drill a 1/8 inch holethrough the side of the barrel,and thread it for a 6-32 screw.(This is a set screw, not aPutting it alltogether.First, modify thebattery charger bycutting off theterminal clips from thebattery cable. StripPhoto 4. The electrode is made from anthe wires and solderinexpensive soldering pencil handle. It canboth of them into one also be made from a wooden dowel or otherof the guitar plugs.insulating material.(This may be a tight fit-- be sure you checkcritical measurement -- useall the clearances in the plug'swhatever you have that willshell before you solder thehold the carbon rod in place.)wires.) That completes theThe rod can be sharpened to apower source!fine tip in an ordinary pencilsharpener. Carbon, after all, isNext, make the electrodethe same stuff a pencil is madehandle. Take apart theof, minus the hardener and thesoldering pencil, and disconnectwood. The fine point willthe cord from the heating tip.permit you to focus the heatright where you need it.Now, connect all the pieces ofthe electrode: thead the cordinto the bottom end of thehandle. Push one of the wiresthrough the angled hole, andmove the other all the waythrough the handle and out theother end. Solder the lowerwire onto the alligator clip andtie a knot in it to keep if fromfalling out the bottom of thehandle. Connect the wire onthe upper end to the carbon rod.If you’re using carbon cuttingrod, it will be coated in copperand the wires can simply besoldered on to the copper coat.Otherwise, you’ll have todevise something that willtransmit the electricity to therod and still permit changing itshould it break. Onehomemade rig uses telescopingbrass tubing to adapt the rod tothe handle. Winding ten ortwelve turns of thin copperwire around the rod would givea good place to connect thepower wire; this can beclamped down firmly by the setscrew for positive contact at alltimes.Finally, you’ll need a footswitch to give you control overthe power and leave both handsfree to work. Use heavy-dutycomponents in this part, oryou’ll find yourself rebuilding itafter the switch or the wiresmelt from the high amperage.Take a 2x2x4 inch aluminumproject box (a two-part box forelectronics projects) and cut thesides of the half with the