Q. I have wheeled a doorskin for my 1940 Chevy truck, which will be butt-welded just below the beltline. Can you give me a basic rundown on doorskin installation?
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A. This is a great question, since many classic truck builders need to repair or replace damaged doorskins. First, carefully check the fit of original door on all four sides. If the hinges are sloppy, it will be impossible to accurately check the gaps, so correct any hinge problems before moving forward. Your goal is to do whatever is necessary to get the original door to fit the door opening as well as possible. In some cases, you might need to use a hydraulic ram in the door opening to reshape it to fit the door. It's not uncommon for a door opening (which is normally rectangular) to become a slight parallelogram, which will definitely lead to uneven door gaps.
Once you're satisfied with the fit of the original door, place your new doorskin over the door, hold it with clamps, and scribe the top edge of your doorskin against the old metal beneath it. Be sure to make a couple of "witness marks" that will make it easy to reposition your new skin right to left after the old skin is cut away.
With the new skin still clamped into place, make a light scribed line around the front, bottom, and back of the door. This line will be used to position the flange you'll be forming on the doorskin edges, so strive for the best accuracy you can manage. Note that this is not the actual bend line, since if you do bend the metal on that line, your doorskin will be one metal thickness too large all around the door edge.
The actual base of the bend will be slightly inboard from your scribed line, and there are many factors that affect how far inboard you should go. While it will be at least one material thickness, you usually need to go a bit more; the amount is governed by the thickness of the metal, and the tools and technique you use to form the flange.
I recommend doing a small test piece to understand how this will work. Start with a piece of metal 6 inches across, and scribe a line ½ inch from the edge. Now, form a 90-degree flange right on this line, then measure the finished width of the flanged part. It will be something over 5½ inches, and the amount that it is oversize will tell you how much inboard of your scribed line the true bend line needs to be.
With the actual bend line established, you can trim the doorskin outside of this line, which will determine the width of the flanges you'll be forming. Make your new flanges the same width that the original doorskin had.
The flanging can be done many ways, but I like using Vise-Grip pliers for this. Be sure to select ones with smooth faces, so you don't make unnecessary marks on the metal. Start at one corner, position the nose of the jaw on your bend line, lock the grip, and rock it up about 10-degrees, then release the jaws, move over a short distance, re-clamp the pliers, and rock the metal up again. Go around the entire door edge in this way, and then repeat the process, going to 20 degrees. Continue in this manner until you're up to 40 degrees or so. Once the flange is at 40 degrees, you can speed up the process by using a hammer and dolly. Select a dolly with a sharp square edge, hold the edge of the dolly at the base of the flange, and hammer the tip of the flange to bring it up to 90 degrees.
Now you can remove the old doorskin, position the new doorskin into place, and tack-weld the top seam. Be sure to align the witness marks you made previously. Next, start hammering the flange down toward the inner doorframe. I like to test fit the door at this stage, before the flange is hammered tight, to see if any adjusting is necessary. If everything looks good, you can finish weld the seam, and tighten the hemmed edge by hammering against a flat dolly.
There is a new book titled Sheet Metal Fabrication written by Ed Barr, which has a superb tutorial on installing doorskins!
You can email your questions to Professor Hammer at email@example.com, or mail to Professor Hammer, c/o CLASSIC TRUCKS Magazine, 1733 Alton Pkwy., Irvine, CA 92606. You'll receive a personal reply! We'll print your name and city unless you request otherwise. Ron Covell has made many DVDs on metalworking processes, and he offers an ongoing series of workshops across the nation covering all aspects of metalworking. Check them out online at www.covell.biz, or call for a current schedule of workshops and their free catalog of DVDs. Phone 800-747-4631, or 831-768-0705. You can send a request by mail to: Covell Creative Metalworking, 106 Airport Blvd. #105, Freedom, CA 95019. You'll also enjoy Ron's YouTube channel: youtube.com/user/covellron.