Guys, my project is off topic but the principal of what I am trying to accomplish is very much apart of what we talk about on here all the time. So with that said I will not elaborate on the project. I will focus on what fits here. I am starting with a flat sheet of 20 gauge sheet metal. the surface area is 5 foot by 6 foot but is broken up into smaller sections with support structure. The sheet metal is attached to the structure so for this purpose we are only dealing with about an 15"x 24" area. within this area I want to push in an area equal to one of those aluminum gas door piece like you get at the local auto parts store. I assume they are made to replace stock gas doors on newer pick up trucks as a dress up item. I am using it as a gas door where one does not currently exist and is a completely custom build. My initial assessment is to make a depression in a piece of sturdy plywood that conforms to the gas lid + 20 gauge sheet around and behind the piece. Am I correct in this or do I need to add extra space? I really want to learn how to do this as my on topic ride is next into the shop and the more technique I can learn leads to better workmanship on it!
I think what you are saying is you want to form a hole with an offset so that you can use a gas cap door and have it fit flush. You want to use wood to do this. Maybe two pieces of wood, one male, one female and somehow press this shape or pound it with a hammer. NAH You must remember this, the wood is softer steel or aluminum. Even if you use hard maple. To have this door fit flush, the metal needs to be offset. That means the metal must stretch and this is where wood fails. Make dies out of metal and tap away.
Not to argue with Woodildo but wood for a hammerform works fine for what your are trying to do (simple strech), I've done it many times. Hammerforms do need to be 2 pieces, one that your hammering a shape into and a top that holds the metal down with clamps so you don't distort what you don't want to shape. If you want to get into metal forming there is a book out by Fournier (spelling?) thats preety commen to find at local book stores and parts stores called sheet metal basics or something like that that has lots of tips on hammerforms and other techniques, worth picking up.
yeah i was gonna suggest the DVD by ron covell and ron fournier called hammerformig basics. watched this DVD a couple of times then made some rust repairs for my O/T project with great success
Thanks guys, was considering using marine plywood for the "mold" given its multiple layers it seems more rigid than most boards I have found. I will see if I can find that DVD or the book, always looking to add to my library. I will see what I can accomplish and maybe I can post some pics when I get closer to ready to do the forming.
A hammerform will do it, but you'll want the hardest lumber you can find to make it with because 18 guage CRS is going to put up a bit of a fight. You might also consider making the recessed area out of a separate piece a little bit larger than the recessed feature first, and then weld it into the rest of the panel after it's finished. A smaller part will be much easier to clamp together and deal with in the hammerform, as opposed to trying to perform the same operation in the middle of a large sheet. I thought I'd suggest this, as hammer-forming will often try to gather material from the surrounding areas instead of stretching the material within the hammerform shape, which can result in ripples and stresses that will migrate into the rest of the surrounding panel. This effect won't matter much if you make the recessed area out of a smaller part first. Ken
Hey, So if I understand correctly, you wanna flange or joggle upon which your new gas door will sit in the middle of this 15X24 piece of 20 gauge? You could go the plywood or MDF hammerform route, but I'd probably cut some .125 steel plate to the O.D. of your opening, complete with the correct radius for the corners, rough cut your panel opening, clamp the .125 plate into correct alignment, and ''flow form'' the part to a good looking '' die stampped '' look. Flow forming consists of plastic, rubber or wooden tooling pieces on the end of an air hammer bit, and leave no tooling marks if done correctly. Once you've formed the joggle, you can trim the opening to size and planish out any waves caused during forming. " Swanky devils C.C. ''
The whole problem from the first time I skinned the project was that welding warped the metal and created a body putty nightmare. Granted, my inexperience led to both problems but I have learned from them and do not plan to put the welder to this sheet metal at all, if I can help it. It is only 20 gauge and hammer forming seems to be the way I need to go. I can try to make a positive and a negative mold and bolt them together through the eventual opening and work with that and hammering to achieve the results. You have me thinking this through from a different perspective than before, so very helpful. Also trying to decide a way to finish the window openings. Currently I have flat auto safety glass being bonded inside the sheetmetal with the metal being flat with the opening cut into it and a rubber U channel covering the metal edge around the windows. I will try to post a pic of this tomorrow.
Got lost, back again. That is the idea behind this form and others. To get you to think beyond the end of your nose or your comfort zone. Woodildo
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