Custom Body Work 101: Filling Trim Holes With a Welder
A common part of custom body work involves filling in any and all unwanted holes in a vehicle's exterior sheet metal. And by common we mean that just about every classic car will have a few holes that will need to be filled when removing trim. The best method to fill them in is welding.
Custom Body Work 101: Filling Trim Holes With a Welder
Welding is an art form and different situations require different welding techniques. Stitch welding with a MIG welder tends to provide the easiest, most effective solution. Stitch welding, as its name suggests, consists of applying a series of small spot welds along a seam much like a short line of stitches. Scrap pieces of copper as the backside helps to fill holes. Copper is ideal as steel MIG wire won't stick to it and thus it can be easily removed once you're finished and it acts as a valuable heat sink.
For holes smaller than a pen's diameter, begin by taking an angle grinder and carefully cleaning the area around the hole. Then use magnets to secure a copper backing on the opposite side of your work site. Heat up your MIG welder and choose one side of the hole and fill it with a tack. Move to the opposite side of the trim hole and make another tack. Then again to that first weld to add another tack upon it, trying to slowly create a bridge that joins the opposite sides of the hole with welds. Be patient and go slow as excessive heat can warp the sheet metal (although the copper backing will help reduce heat).
Dressing with a Body Hammer
Once you have completed all necessary welds, the next step is to use a body hammer to dress them. This requires hitting down high spots to increase the weld's surface area. A grinder should then be used to even out the weld as much as possible before applying any body filler material.
For trim holes larger than a pen's diameter, cut out a scrap piece of metal to fill in the hole and use one or two magnets to hold the piece in place (you should also still use copper as backing). Now it's time for the stitching. Choose a starting position and make your first tack. Pull the welder back and allow the weld to cool slightly before continuing on with a second tack or stitch about a millimeter to the right of the first. Continue around until you have a complete, even series of welds. Dress, grind, fill, and finish as with smaller trim holes.
Need Welding Help? Contact CHRA
Welding is a lot of fun and we encourage every automotive enthusiast to try their hand at it. But if you have big custom body work you want some assistance on or you want precision filling, never hesitate to bring the work to us! CHRA is your local custom body work shop for all welds big and small.