FEEL FOR DENTS AND WAVES-One of the most utilized skills that is developed by a bodyman is the ability to feel a panel and tell if it is straight. This takes practice. One way to develop this skill is to use reflected light to sight down a body panel and look for a wave in the reflection which indicates a dent. Locate that area and, with your entire hand as flat as possible with fingers together, lightly rub your hand back and forth in large strokes over the area and see if you can feel your hand move as it passes over the dented area. A great way to “train” your hands is to do this process with a clean shop rag between your hand and the panel. This will let your hand glide over the panel and the dent will become easy to locate.
GUIDE COAT-Always use a guide coat. It is used to tell when a panel is flat, smooth, free of large sand scratches and completely sanded. It will remain in low spots and will tell you when an area is not truly flat. . I use it as a guide on body filler, on primers and on top coats for color sanding operations. Commercial guide coats are available, but a spray can of primer in a contrasting color works well.
SANDING-For the smoothest, show quality finish, never, never, ever sand anything with your bare hand!! Always use a sanding block. Your hand is not perfectly flat and will cause waves that are only visible when a panel is glossy. This happens when your fingers press through sandpaper and carve grooves in the surface being sanded. The use of a proper sanding block will prevent this from happening. There are many different types of inexpensive sanding blocks on the market and it is a good practice to keep a variety of them close by when sanding.
WELDING CLAMP-One of the strongest, most versatile clamps I’ve ever used is a 2 cent sheet metal screw. Position the panels, drill a small hole through both panels and insert a screw. They work in areas where normal welding clamps won’t, like where there is no access to the back of a panel, or in door jambs so you can shut the door to check for fit. They will also draw panels together as they are screwed in. After the panels are joined, just remove the screws and weld the holes shut.
BUFFING-To prevent buffing through edges or character lines, cover them with a single layer of 1/4″ masking tape. When buffing near character lines or the edges of a panel, never buff across the edge. Always buff with the direction of the edge. After the panel is polished, remove the tape and make a single light pass with the buffer.
STRAIGHT EDGE-A great tool to have on hand when doing hammer and dolly and plastic filler work is a metal straight edge. You should look at, and feel a panel for waves and dents, but correct overall panel shape is sometimes a little trickier to determine. Either a 2′ or 3′ aluminum or steel rule is very good for checking to see if character lines are straight or if there is a high spot or low spot in the middle of a panel. They are also great for checking a panels crown. (That’s the slight bulge in a panel that helps give it structural strength)
WINDOW RUBBER AND DOOR SEALS-An easy way to install any rubber seal or bumper that rides in a channel or snaps into place is to spread on a bit of liquid soap or waterless hand cleaner, ( the kind without the grit). This will lubricate the rubber enough to let it slid into place , it’s easy to wipe off, won’t harm the rubber and won’t harm the finish.
DUCT TAPE PROTECTION-Anytime you are sanding or grinding on a panel in an area close to another panel, (like the edge of a door next to a fender), it is a good idea to protect the panel with a couple layers of duct tape. Just run it along the edge adjacent to the panel you are working on to prevent any accidental damage.
WELD THROUGH PRIMER-Whenever possible, apply a coat of weld through primer to both sides of any panels that are to be sectioned. Weld through primer is a zinc rich coating, (available at good auto body supply stores) that will conduct current from a MIG welder, making it possible to join panels and will provide corrosion protection an lap joints and on inner panel surfaces. This is especially important on lap welded seems as the overlaid panels create an area that is ideal for rust to start.
STEP DOWN-The correct way to make a lap joint is to make a step down flange on one of the panels. This is done with a step down or flange tool, either air powered or hydraulic. This will keep the outer surfaces of both panels on the same plane, making a smooth transition. It also makes a very strong joint and, especially when used on a large flat panel, will give the panel strength and minimize heat warpage from welding.
LAP JOINTS-Never make a horizontal lap joint where the outer panel is laid over the replacement panel, with the seam facing up. This will create a natural water trap, (see illustration below). Condensation inside a panel will drip down and collect in the seam and it will eventually rust and fail. Always use weld through primers and whenever possible, after welding and grinding, coat the inside of the sectioned panel with zinc primer or undercoating.