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Old 02-13-2014, 02:39 PM
John Buchtenkirch John Buchtenkirch is offline
MetalShaper of the Month October 2012
 
Join Date: Jul 2009
Location: Glen Cove, Long Island
Posts: 1,675
Default panel reading for metal finishing

After reading some recent posts I realize that some members don't have a good understanding of how to read a panel when they are trying to straighten it, an idea that seems very foreign to me because I came up through the auto body trade where it was somewhat of a necessity. This is how I do it, others may want to add variations of their own or their personal tricks and tips. >>
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The first photo shows a pickup truck roof skin that had and air horn mounted on it, there was two holes to weld up plus some damage from the weight of the horn. The trouble area is already primed and cross filed, I use the lightest coat of Krylon primer, it dries quickly and wipes off nicely with lacquer thinner if needed. The yellow lines show the direction of the filing and if you look carefully you can see file lines in the primer. The idea is to only file off the primer, not any of the metal. I use a dull vixen file blade in an adjustable holder, I crown the file so one half to three quarters of the file touches the panel. When filing I always stroke the file at 20° to 30° angles off the centerline of the file body, it files fine like that because of the curved tooth designe of vixen files. If you find that you are filing metal off the panel your file is either too sharp or you are pressing downward too hard. >
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You CAN NOT file a panel with sandpaper and a sanding board, they just do not cut accurately enough for this type of work. Sanding boards have foam backers and are designed more for blending auto body plastic than cutting 100% straight. Obviously the shiny areas in the photo are high and the areas untouched by the file are low but I always confirm that by running my hand over the panel anyway. If I'm trying to get a panel extra nice or even ready to be chromed I may mist coat it and refile it several times through the job, there is no rule that says you can only do it once.>

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The second photo shows the direction (arrows) of running my hand over a panel. The idea is to feel for waves, low areas and high areas, not the texture of the metal so you want to feel more with the palm of your hand and underside of your fingers, not necessarily with your fingertips if that makes any sense. I feel the panels in several directions but always by rotating my hand and using side to side motion (like you sand a car), I never stroke my hand parallel to my fingers, a bad habit to get into.>

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The third photo is the underside of the roof skin with the arrows showing the two holes I filled.>

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The fourth photo shows the underside after it has been primed and filed for reading surface irregularities. It shows that you can also file and read concave panels by crowning your vixen file the correct way. You can even use a shrinking disc on slightly concave panels but it has to be one of the more flexible ones without the safety edge. Yes, I know they are dangerous but you have to let the disc stop spinning before you lift it off the panel. Keep in mind the closer the panel gets to straight (should be called “true flowing curve”) the harder it is to read.

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My final thoughts are that this is geared towards fine metal finishing, not production body work and also there are variations on this, none of this is written in stone but there’s some basic ideas here to get some of the younger guys pointed in the right direction. I will try to post a few more tips tonight or tomorrow, right now I've got to dig some damned snow. ~ John Buchtenkirch
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John

Last edited by John Buchtenkirch; 02-14-2014 at 10:52 AM.
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