Here is my tech post on making a hammer formed sheet metal piece. I needed to build a new interior armrest panel for a '64 convertible Nova. The new and old piece for you to get an idea of where we are going. I use MDF for most of my hammer forms as it is inexpensive and easy to work with. Sorry I didn't get pictures of cutting out the MDF but I think you can figure that part out. Remember the form has to be exactly the shape you need as the sheet metal will reproduce the form exactly. I made a paper template of the original part so I knew how big to cut my sheet metal for the part being reproduced. I hold the paper down with some small magnets and a few weights. I marked the sheet metal with a Sharpie. First I trim away most of the excess sheet metal with my aviation snips leaving 1/8" to 1/4". Then I come back and cut it right to the line. And lastly I de-burr the edge with a file. Using the screws that align the two haves of the hammer form I mark my sheet metal and then center punch the marks. More in the next post. Give me a minute I type slow.
Next steps. I use a Whitney style punch to punch the alignment holes because it is easier to use then a drill and it puts the hole exactly where I want it without walking when drilling. Then position the sheet between the two forms and screw it together through those alignment holes. Mark the metal that is to be formed as to which way it is to be bent. I have formed more then one part the wrong way. Now use as many clamps as you can to secure the three pieces. If you fail to clamp it tight enough the sheet metal will walk in the form and/or you will break the MDF as you hammer against it. Always start on the easiest part (straight or least curved part) as it puts less force on the form and stops the sheet from creeping later as you try to shape the more difficult areas.
And More. Move your clamps around and start on the side that needs stretching I use a steel body hammer for this step as it is harder the the sheet metal and will help to stretch the metal around the form. Be careful to not strike the MDF as it can leave a mark that will show up later if you plan on making more then one piece. Here Is the hard spot. I need to shrink the sheet into a tight inside radius corner. I start the bend slightly with the steel hammer as the sharp sheet edge will dig into the softer plastic mallet. Once the edge is started down switch to the softer hammer (plastic, wood or rawhide) and finish the the bend. You will need to hammer the most in about the center 1/3 of the bend here as this is where most of the shrinking will occur. The sheet formed all around the form and the clamps removed. The part!! Now it's time to add the holes and get to work on the other side. Hope everyone enjoyed. If you have any questions ask away as I am sure there is something I left out. Jaysin
nice post, I have not used mdf yet, I mostly use oak for small pieces. the mdf holds up o.k.? dont forget the hammer form needs to be smaller than the part.
Hey Jaysin, Great tech post- Maybe mention that in areas with tight radius or shape changes, you can get the metal to conform better by anealing it. Heat those areas with a torch to a low red heat and strike with a convex shaped hammer faced head. Swankey devils C.C. "Meanwhile, back aboard The Tainted Pork"
Excellent! Thanks for posting. I'm also curious as to how well the MDF holds up. I guess it really depends on the thickness of the metal as well.
Thanks for the post. As a novice, I've been looking for a non-threatening way to try out some sheet metal forming and your post makes me feel confident that I could probably succeed. I appreciate all of the details. The tip on cutting close with the snips then cutting to the line wouldn't have occurred to me. One thing I'd like to contribute. I work with stained glass and make cutting patterns all the time. If you use manila stock (same material as file folders), you'll have a stiff pattern that's much easier to trace accurately than a thin paper pattern and is long-lasting as well. I'm confused on one point. You identify your work on the outside edge as stretching, and your work on the inside curve as shrinking. I'm picturing it in my mind and it seems to me that the metal in the outside curve flange is getting thicker, and the metal in the inside curve flange is getting thinner. So it sounds backwards to me. Or am I misunderstanding the terminology? Thanks, again for the post. John.
Jms~ You caught me. Yea, the outside radius is shrunk and the inside radius is stretched. It's no excuse but I am sick as a dog right now and the brain could be working better. Curious Rash~ I have had great success on up to 18g and have had good success on 16g (steel) much beyond that you would have to make metal forms and use heat. But I don't have any real use for shaping sheet any thicker then 16g. On annealing, Steel sheet will not become much softer if you heat it and it will only anneal if it it cooled very slowly. If you throw it in water or cool it with compressed air it will become slightly harder then before. On aluminum sheet annealing works very well, and will be very beneficial on both inside and outside radius. The MDF holds up well for about 7 or 8 parts (18g or less) as long as you are careful not to strike the form itself. If your part has round corners and you use a router or sander (etc...) to round over the edge then it will usually last for 10 or 12 parts. Hope this helps. Jaysin
"Mark the metal that is to be formed as to which way it is to be bent. I have formed more then one part the wrong way." That may be the most important line in there. Guilty of that more than once myself. Great tech article!!
Great tech, good explanation! You can use a variety of things to get those inside corners, rounded chisel bits, pieces of hardwood cut to the right radius, ballpeen hammer, old hammer handles....
Everyone, skips details on making the actual hammer form. If I could make that easily I could probably eyeball the metal and freeform it a la Marcel Delay.I did learn some good points from your post. thanks
Short, foot long pieces of pipe (not exhaust tubing) work good on inside radius curves. Select a pipe diameter close to what you need, set it on the exposed sheet metal, then strike the surface of the pipe opposite the sheet metal gradually angling the pipe downward as the curved flange takes its shape. Works great - and no hammer marks to deal with!
Thanks for the great tech!!!! I will save this one too. Have a few ideas for the "Hairy Cherry" that I can use that technique!!
Nice job, and nice pictures and description! I would add that every time I make something with a hammerform, the metal tends to spring back slightly as you try to hammer it down over a tight bend. Once you get a feel for how much it springs back, you can make the hammerform slightly smaller so that when it springs back, it springs right where you want it to. You can use a home-made T-dolly to finish pounding over some radiused corners if they don't wind up exactly where you want them.
Nice post. I'll use some of this info when it gets warm enough here to get back into the shop.(no heat yet) I have some oddball panels on the F-truck that are rusted & not reproduced. This info will help me to build them myself.
Great tech Post.I have made alot of hammer forms also and one thing I have found that makes a big difference is using (DQ)draw Quality steel also known as alum kilned which can be hard to find at local steel suppliers.but it is the same steel used to build most cars so if you have a old hood or roof around you've got some easy to get (DQ) steel
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