I have bought a pair of forked head lamp mounting brackets which are cast brass repro's. The forks are 7" on center, and I need to widen them to 8-1/4" o.c. to accommodate a pair of bigger lamps. I've never tried to bend this type of material, so I'm asking the vast multitude of experience here on the Forum for advice on how to do it. Should I heat it, or bend it cold, or what? Thanks for any info.
Cold= broke. Heat them and gently widen them.
Thanks, Uncle Jack. That was quick!
I think you were lucky to find those. Last time I checked several years ago, all the repros were potmetal. One broke on me, and the brass headlamp was dragged under the car. Luckily, I was going only 25 on a side street.
I lucked into brass ones at swap meets.
Don't try and bend them when hot. Brass hot tears or easily breaks when hot. Yes, they need to be heated to a dull red then either quenched or allow it to air cool to anneal them first. Brass tends to get harder and more brittle with age, the reason 90 year brass headlights start cracking. If the forks are fairly new they might be ductile enough to bend now but heat them to be on the safe side. Bob
Uncle Jack's advice may have been a little too quick! Brass is bent cold. Aneal by heating brass to a dull red and quenching in water. Gentle bends only, as the brass work hardens,however the peice may be annealed several times as necessary. Better to anneal the peice more than needed.
Thanks to everyone for your help on this. From the posts here and emails, most are of the opinion that the brass should be heated, then cooled, then bent. Reheating along the way may be a good idea. I reckon I'll give it a go and see what happens.
Bob and Fred, thanks for clarifying that. I once tried to bend a brass steering wheel spider hot and broke it. I was hearbroken. Later, I was told to heat and quench brass before bending, even cast brass. Too late for the spider, but won't ever forget the lesson.
Unlike steel, the quenching does not really have much affect on the softness and bending. If in a hurry then quench it cool, if not then have a cup of coffee and wait. I find that it is safer NOT to handle something that is hot so usually I just wait. What is important is that the brass be brought up to a hot enough temperature so that annealing (softening) takes place. If you do not heat the brass up to that temperature it will not be soft and can break. In any event you do the actual bending once the thing is cool. I find the easiest way to get enough temperature to anneal the brass is to go into my garage and turn out ALL the lights at night and then fire up just the torch with a "rosebud" tip on it to spread the heat out on the part. As others have stated, you then heat up till the part is noticeably red in the dark and then let it cool. If you watch the metal itself and do this very often you can actually see the border between the annealed area and the hard area. I have made windshield support rods where I only wanted to anneal the ends were the part was formed and I could tell when I had annealed the end by the change to the metal coloring pattern under the torch. Can't exactly describe it but those who do a lot of annealing of brass know what I am talking about. When you spin brass parts you have to stop and anneal many times. Its kinda fun. Whether you anneal the entire part or only a part of it, the final coloring will be uniform all over but while the torch is there you can see a difference as you perform the annealing.