What is the best way to de-dent things like this horn front? Best done cold, or hot?
Ralph - This might sound like a "smart*ss" answer, but I really don't mean it that way. I've heard that a good approach might be to take it to a musical instrument shop as they work on similar type brass stuff all the time. Or, if you're dead set on doing it yourself, maybe just talk to someone at a music shop or maybe even a high school band teacher, as they'd probably have some idea too. Just a thought,.......harold
I took it to a brass instr. repair shop, and to a brass instrument manufacturer last week. The repair shop was too busy with stuff they know, and the manufacturer shop rate is $85/hr. Being retar'd, my time is worth a little less than that.
I also have a brass speedo case with cracks to be fixed.
The First thing to do is study now to anneal brass, then it can be worked like a body panel.
First anneal it. Heat it nearly red hot and quench it in water. This will make is soft and more pliable. Use a soft face hammer or a body hammer against shot filled leather bag. Be patient - work slowly and you can achieve pretty good results.
Darn East Coasters type faster
AN old ball bearing,welded to a rod,which is then clamped in a vise and you can "rub" out a lot of dings.
The horn rim on my '12 is all beat up like that too! What's up with these things?
People bumped them taking the hood off the early brass cars.
In regards to fixing the cracks I bought a brazing wire at a local jewelry supply that is 90% copper and 10% phosphorus. I have brazed copper and brass with this using "Handy Flux" and a propane torch. The phosphorus lowers the melting point considerably ( about 1100 F). This way you have little risk of melting the object. I have worked a lot of copper and brass using a piece of heavy leather over a wood surface. For a hammer I used a cheap rubber/plastic faced hammer with a bit of curve ground onto it. The right answer is what works for you. I would buy/find a bit of sheet brass/copper and play with it. I took a one week intensive course (8hours a day) at a local art college. Sure helped me in a hurry
I wouldn't suggest annealing the part until you try to take out a dent and see how out it reacts. My experience on most brass lamps and horns is that the brass is already pretty soft and not hard to work with.
Jack has a good suggestion about the ball bearing and rubbing it across the dent to force it back up. Another trick is to round the end of a wood stick and rub it over the dent to press it out. Small hammers and dollies can also be used to work out the dent. Rub a piece of sandpaper on a flat block over the dent to highlight it and check your progress as you work on the part. The process is basically the same as removing dents from body panels.
The horn pictured was an Ebay purchase that we restored for Jim's 1911.
You will need to heat it up enough to remove the screen and the lumps of solder holding the screen. Those lumps will be in the way of your efforts to straighten.
I've straightened a few horns, and I use a dowel pin, or a piece of dowel rod with the end rounded. I have also used metal punches, but have tapped ever so gently. I then use a piece of wet or dry, and a rubber sanding pad. Whatever works. I think patience is the key. The screen is still available.
I have had great results by gently using a chipping hammer or small tack hammer on the underside. Use a file to show you where the high spots are and work ever so slowly. When the file shows you that you have it right, use different grades of sandpaper until autosol removes all the scratches. The results can be stunning. Practice on something that's scrap first.