Cold Chisel question

Henry of Bexley · Post by **Henry of Bexley** » Fri Dec 10, 2004 5:55 pm

I have begun cutting out pieces for my next project. Since I really had no other recourse to cut the sweeping curve in Gothic (my only power tool was a metal cutting circular saw- you have to be REALLY good to get any nice curve with one) I started cutting cold chisel. After cutting out 3/4 of my BP, I have decided that anyone who would do this regularly is a masochist... having said that, here's my question.

Does cutting with a cold chisel cause work hardening?

Only I would write a paragraph to explain why I am asking a question so simple... I hearby apologize for my verbose-ness.

Thomas H · Post by **Thomas H** » Fri Dec 10, 2004 6:37 pm

I don't think it does, most of the hardening is one in the forming process. Even then it is only a small amount of hardening. I use a cold chisel that is razor sharp for thin gauges, most grinding will take away what little hardening has been done. hope that helps.

RalphS · Post by **RalphS** » Fri Dec 10, 2004 8:51 pm

A cold chisel causes very localised, and hopefully, quite extreme work hardening. Which is what you want if you want the steel to break exactly on your chiseled line.

The way I have used a cold chisel to cut out certain forms is actually reasonably fast. A sufficiently sharp chisel, with a rather wide cutting angle (much shorter/broader angle than on a knife) is used to cut through half to 2/3rd of the thickness of the plate in one blow for each segment. I use a shorter chisel for the tighter curves, and a somewhat longer for the straighter parts. Use the last part of the chiseled depression to make sure your next cut will line up nicely.

With a little bit of attention and routine this should work quite fast.

Now comes the fun part: clamp one side of the chiseled steel close the the cut in your vice, and bend the other side back and forth a few times untill it breaks on the chiseled line. This will happen eventually due to work hardenening and metal fatigue, usually in a few bends already. Continue with this untill you have cut out everything. Sharp corners and points may need a few extra blows with the chisel to break loose completely.

The advantage of this method is that it can be applied with very little distortion to the piece, if done correctly (e.g. trimming the edge of a helmet, where the shears would deform the helmet too much), and could even be used to cut out holes in the middle of a sheet (try that with a beverly!).

Disadvantages are obvious, and plenty of better and faster alternatives exist in most cases. But if a chisel is all you have, you can come a long way with it.

Hew · Post by **Hew** » Fri Dec 10, 2004 9:58 pm

Would a narrow chisel, say, 1/4" wide, be easier to work with? I'm thinking more force per linear inch, and smoother inside curves.

Thomas H · Post by **Thomas H** » Fri Dec 10, 2004 10:01 pm

Mine is about 5 inches long.

Henry of Bexley · Post by **Henry of Bexley** » Fri Dec 10, 2004 10:17 pm

I think he meant width, dude...

The only other problem/annoyance I am encountering is hammer arm fatigue... this MAY just be because I'm cutting street signs... hehe. Any hints for reducing fatigue?

I really need to invest in some GOOD hearing protection too...

Thomas H · Post by **Thomas H** » Fri Dec 10, 2004 10:21 pm

oh right. do warm ups before starting and do weights at the gym. a smaller hammer helps as well.

RalphS · Post by **RalphS** » Sat Dec 11, 2004 5:24 am

Yeah, as Thomas said; it's a bit like metal fatigue: just heat it up to red heat, and let it coold down slowly. Do not dip your arm from red heat in cold water, which in the worst case may crack it. If you continue working your arm beyond the point of fatigue, it may crack or even break completely. You don't want this, you'd ruin a good tool!

Kidding aside, the right working height and position also helps a lot. Do some stretching afterwards.

LordWulf · Post by **LordWulf** » Sat Dec 11, 2004 5:35 am

I generally do cutting in the morning, have me a nice lunch, grind the edges, then do the hammering...... that way ti kind of spreads things out over the days and my arms don't get tired......

Ivo · Post by **Ivo** » Sat Dec 11, 2004 8:05 am

Hello.

This might be stupid, but...how about drilling a series of small holes and subsequently cutting the material between them with a chisel? At least that is what I am doing on concave curves for I only have a straight- sided shear which allows for clipping convex curves only. Quite a ot less material do be cut and much more friendly to my elbows.

Regards

Ivo

Henry of Bexley · Post by **Henry of Bexley** » Sat Dec 11, 2004 9:33 am

Okay... so it DOES cause work hardening on the edges. Would it be a good idea to anneal before trying to roll my edges?

Thomas Powers · Post by **Thomas Powers** » Mon Dec 13, 2004 3:28 pm

The work hardened area is only where it is deformed by the chisel, most of this will disappear when you clean up the edge with file or grinder, it should not affect rolling the edge unless you are trying to bend the very outside of the edge, say the last mm or two. Which is not done in the rolling I am familiar with.

Thomas