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Re: Handheld Air Hammers
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Posted by Chris Ray on January 23, 1998 at 20:54:50:
In Reply to: Handheld Air Hammers posted by Steven Bronstein on January 23, 1998 at 19:29:42:
Steve: I have a range of hand held air hammers that I use on occasion and they work just fine on cold steel. Now I have a friend who uses his hand held hammers for carving heavy pieces of hot iron and does a very nice job of it.
For carving hot iron you should have a good pair of heat resistant gloves (not leather) something like the new kevlar gloves are probably best since they can protect you from a lot of heat. When carving hot iron, because of the compactness of the tool, your hands are pretty close to the hot metal.
Since I use these tools for carving or incising cold iron I can talk a little bit about that here. For whatever reason, I haven't yet tried these tools working the metal hot and one reason is that I don't need to since these tools carve into cold iron quite deeply. You'd be surprised just how far you can go with this equipment without the use of heat.
I have about a half dozen air tools that range from a light duty zip gun to a heavy duty air chisel, all are pistol grip devices rather than in line ones. When starting to carve I start off with the lightweight tool to lay down a beginning track then may use the medium duty tool from that point to completion. When I need to incise very deep lines then I switch to the heavy duty tool and can nearly cut right through a 3/8 piece of plate without any heat or annealing although it takes a number of passes to do that. Also the angle or bevel on the chisel determines the nature of the cuts I want to make.
It's actually quite surprising just how much work a medium weight air tool can do since the number of impacts per minute is quite high. Also it's easier to maintain control with a medium weight tool although the heavier one gives me no problem once I set a deep enough track into the metal for it to follow.
Chisels: I usually regrind whatever standard air chisels I can get hold of. Sometimes I'll even reforge them into special shapes and have even built up welded areas on the ends for blunt ended impact tools used for fullering. Using a steel facing welding rod after building up the mass will help the tool to hold it's shape without deforming. You can also upset the metal at the forge. I don't attempt to retemper my blunt tools after doing that though because of the uncertainty of the hardness of the metal. I wouldn't want to have any fractures coming off an improperly tempered tool. So far I haven't had any problems with the steel holding up under impact.
The difficulty I encounter with the air tools is being able to firmly clamp the material to a heavy iron base plate. The vibrations from impact usually causes the metal to move no matter how tightly clamped and also the metal deforms somewhat causing a partial lift in some areas while working. You just have to get used to working around these problems. So far I haven't found or devised a suitable clamp that I can use for this type of work. What I use now is a massive tool holder with a special hold down bar that was salvaged from an industrial lathe but even that isn't perfect. I also have a low stand which holds my heavy base plate so I can stand over the work and lean into the tool when I need the extra pressure.
Ideally a hydraulic or even an air clamp would be best because of the constant pressure maintained but of course these units are bulky and get in the way so I haven't been able to use them so far. If you can find a way to securely clamp your work piece against a heavy plate or even in a large vise then I think you have maybe seventy five percent of the problems solved with this type of work. It is the chatter and bouncing around of the metal that makes things difficult, not the carving itself.
I can't think of anything else to add at the moment. Perhaps others have a different experience with these tools and will share some of thier knowledge with us.
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