FILENAMES: welder00.jpg welder01.jpg welder02.jpg welder03.jpg welder04.jpg welder05.jpg welder06.jpg welder07.jpg DESCRIPTION: These are pictures of a shop built spot welder. Posted by JR North . The following description was provided: ================================================================= Construction notes on the Spot Welder I built for assembling the SS cumbustion chamber in my Waste Oil Heater Project. I'm sure it will have many other uses also. The welder was constructed using 2 surplus 120/240/25V 1.5 KVA transformers. These have 2 primary windings and 3 secondary windings side by side. I got them for $10.00 each. The secondary windings were removed by chucking the transformers in my 4x6 saw, and carefully cutting through the windings flush with the case, being careful not to damage the primary windings. The remaining windings in the cases were driven out with a 1/2" punch. The unit uses a programmable electronic timer, which switches a 40A solid state relay. A foot switch (SW 2) activates the timing cycle. A master dpst switch (SW 1) cuts both legs of the 240V supply. The welder runs on a 30A 240V circuit, using the breaker in the supply panel for overload protection. The arms are 5/8" half-hard brass, and are 20" long. I milled a flat on each, and threaded 3/8"x24 for the screw-in welder tips. The 2AWG secondary cables are attached to the rods with copper lugs, and 3/8"x24 SS bolts and star washers. I made the arm holders from polyethylene blocks. For the lower arm block, Drill the 5/8" hole for the arm so a 1/32" of the arm diameter projects from the bottom. When you bolt the block to the table, this will clamp the arm firmly in position. The block is relieved inside for the cable and clamp clearance. The lower block must have clearance for the arm to be adjusted in and out, to align the tips. For the upper(articulated) arm, drill the block so there is 1/4" of material between the 5/8" hole and upper clamp plate. The block is then sawn in two through the arm hole axis. The material removed by the saw blade will allow the assembled block to clamp the arm firmly in position. The articulating clamp is a Destaco model from MSC. I cut the bottom at an angle, and welded a 2" square flange for bolting it down. Dimensions and angles for the position of the clamp need to be determined from the dimensions of the mounting blocks. When locked, the clamp should apply firm pressure to the welding tips, which must be aligned prior to each weld due to play in the clamp mechanism and flexing of the arms. The secondary windings must be tightly wrapped, and located as close to the primary windings as possible. I used wooden blocks to hold the cable in the secondary slots of the cases. All metallic components of the welder must be grounded. Use 10 GA wires for all power circuits except the foot switch circuit. All components are mounted on a 24"x8" shelf, available finished in white for about $3.00. I used 1 1/2" rubber plugs for feet. Future mods will include couplers mounted at the blocks, so different size arms can be mounted without dissassembling the block mounts. MSC Parts list: timer module: 54023122 $58.26 octal socket for timer: 54036666 $7.40 foot switch: 54097191 $17.10 relay: 54050372 $56.05 welding tips: 62338335 $7.00 Destaco toggle clamp: 06988964 $12.75 Further documentation can be found at: http://www.5bears.com/welder.htm Where I originally got the idea The Pics: Welder00: The schematic Welder01: The transformers as purchased Welder02: With the secondary windings removed Welder03: The set of 24" Arms W-n: Various views Several Pics have been retouched, due to the lack of contrast in some of them. JR North Question or comments: jasonrnorth@bigfoot.com