Welding Quarter Panels with the New Stitch Welder
An old car's fenders are usually in sad shape by the time you start a restoration project. On newer cars (50's and more recent) it's sometimes easier to replace the whole quarter panel than to attempt several patches. We'll explain the steps you'll need to get the car ready for panel replacement, as well as the techniques for using the new Eastwood Stitch Welder to weld the panel in place.
You can weld body panels with oxyacetylene, arc or MIG welders. The oxyacetylene method is the most common but it takes too long to weld and the extreme heat produced causes warpage and distortion on the long panels. A mig leaves a clean weld, works fast and causes virtually no distortion - except to your budget. The smallest migs cost over $900. Finally, arc welding (shielded metal arc) or "stick welding" is fast but most welders are designed for heavy welding repair on frames not delicate sheet metal work. The conventional arc welder throws too much heat and can cause burn-through on sheet metal, however an arc welder is inexpensive, readily available, and easy to use.
The new Eastwood stitch welder tames a standard arc welder by controlling the amperage output to produce a smooth, even weld bead on sheet metal. This unique welding attachment controls the heat so burn through and distortions are virtually eliminated. Any body man knows distortion or warpage is the big problem in welding autobody panels.
The Eastwood stitch welder has several specially designed circuits to reduce or control a conventional arc welder's high output. It can be used in two modes: direct circuit or diode reducing. These settings are adjusted with a small screwdriver at the base of the handle. Don't tighten the screw too much-just make it snug. The other circuit is a solenoid coil, which passes all welding current en route to the electrode. The electrode holder is spring loaded and vibrates. When current passes through the coil the electrode and arc are then pulsed thousands of times a minute to create an interrupted arc. This creates the amperage control necessary to weld thin gauge metal. It can be attached to any AC arc welder that can be set at a low amp output (usually 50 amps). If you can't go down that low, use the diode mode to cut the amp output by half.
Select a welding rod to match the job. The stitch welder will work with 1/16", 5/64", and 3/32" electrodes. For body repair, the 5/64" electrode with the welder set at 50 amps works best. All welds shown in this article were run with our welding system power pack, which delivers a consistent 50-amp output. The stitch welder will work on any AC arc welder set at 80 amps or less.
Using the stitch welder is different from conventional arc welding. Striking the arc is much easier than standard stick welding -it seems to start automatically when laid on the metal. For better weld control, a stringer bead (vs. weaving bead) is used on sheet metal. This bead is about three times the width of the electrode wire and is easily controlled because the electrode is laid on the metal. It also produces a smaller bead for less grinding. The forward motion is operator controlled. The weld bead will run fast and that's good since you create a minimum of heat. Run the weld bead as fast as possible without breaking the arc. Remember, with the .040" thick body metal penetration is no problem. After practice you will be able to direct the arc into the 90-degree angle of a flanged joint and getting good penetration is no problem. After running a bead for three or four inches, check your results. Sometimes the dark lens makes welding difficult and you might be off target. Check your progress often.
Restarting a bead is easy, but all slag should be cleaned from the end of the previous weld. To restart, move to about 3/8 of an inch from the end of the weld and strike an arc. As the arc starts, rapidly move the tool backward until the arc touches the old bead. During these few seconds the arc stabilizes and produces a proper bead. Next, reverse direction and continue a forward motion. The technique leaves a bead that will blend to a virtually unbroken line.
After welding the resulting slag must be removed before you inspect the weld. The slag is a weld by product and helps keep the weld area from cooling too rapidly. Always allow the weld area to cool for a few minutes before cleaning. The base metal is so fine that a standard chipping hammer would put dents in the panel. The best alternative is the Eastwood trim hammer (13146). Its chisel end and 2-oz weight are just right for breaking away slag. To get residue out of nooks and crannies use our cleaning disc. After a bead is cleaned you can spot problems or missed areas and decide if you need to weld more.
Welding automotive panels is easiest on a recessed lap joint. This offset can be formed easily with our panel flanger (31092) so the two panels will be flush. On this joint, the two panels make a path for the electrode.
As in all welding operations, both surfaces must be shiny clean. Use the cleaning disc here because it won't remove metal - just unwanted paint and corrosion. On the reverse side of the car panel, old undercoating and sealer should be removed. The welding heat could set these coatings on fire (always have a fire extinguisher on hand when welding). Cut away all damaged metal with a nibbler and remove spot weld cutter. The spot welder (19098) saves metal by only cutting the top layer and leaves a bottom layer, which is easily ground off. Spot welds in this project were in the rear of the fender and under the wheel wells.
After cutting the panel, you must fit the replacement panels. For this application, we took the rough measurements of where the panel was to be cut and cut the patch panel. Next, the patch panel was roughly fitted on the car over the damaged metal. (NOTE: the wheel well and spot welded sections were removed to assure correct fit.) A marker line was drawn along the edge. Our cutter would be ½" below this to allow a flange joint. The resulting fit was very close and required little additional trimming.
Fit is very important because any gaps will throw off the flush match of the offset flange. To keep the panels in place use our panel holding system (19074). One holder every 10" is usually sufficient. The 1/8" hole remaining can be filled with solder.
After the panel is in place, you are ready to run the bead. Remember, short (3-4") beads work just as well as one continuous bead. For the beginner, this 4" length is important so you can check your work. When you weld with the standard 5/64" (2 mm) electrode the heat-affected zone is ½" to 5/8". This really limits distortion, and we have found it doesn't even burn the paint around the repair area. Be sure to clean all slag away so the weld will be free of debris.
Finish the repair area with a new 36-grit disc. Just lightly touch the top of the bead and gently grind down. Don't get carried away here because the grinder can cause heat distortion and, if you're not careful, grind a hole. A properly welded panel will require minimal use of filler. The weld joint will be tight and completely seal the patch. Always remember to reseal the backside with undercoating and seam sealer because this area is ripe for corrosion.
Developing Welding Technique
The stitch welder requires its own special welding technique. Sometimes positioning your right arm over your left eliminates shaking (for right-handers and vice-versa for lefties). Always start with a ½" length electrode. Just cut with a pair of snips ---the end can be used later. Practice on scrap pieces. This allows you to get used to the feel and sound of the tool. Learn how fast to run the bead - running too slow will cause burn through. Don't try to fill the hole (it wont work); leave this job for body filler. Don't be alarmed if the pulsing stops after a few seconds. After the bead starts, this is normal.
If you have trouble starting the arc, check the following:
1) Connections for ground and stitch weld. If the connection is poor, it will seriously impede welding performance.
2) Electrode choice: If you have an improper grade electrode, the stitch welder won't work.
3) Amperage settings: If the welder's output is too low, an arc cannot be maintained. Sometimes some persistence is necessary because lower settings produce less distortion-causing heat.
4) Practice, practice, practice! After about an hour or less most welders can master the stitch welder. Don't attempt a patch panel repair without previous experience on scrap panels or metal of similar thickness.
Follow the same safety precautions as you would with an arc welder. Proper lens and shield, long gloves, long sleeve shirt, proper ventilation, etc. are musts.