Need to Make Spring for Welding Work Clamp

[Crunch]

Hello, all,

The coil spring in the 300A work clamp for my welder recently broke, and since I have some 5/32" spring steel that's almost the exact same diameter as the wire used in the original spring, I figured I'd give it a try. (I just knew the springs from that old bed boxspring would be useful for SOMEthing!)

Anyway, I'm a complete novice at blacksmithing, and just wanted to check with you folks for any tips on making this spring.

In general, I plan to:

1. Heat the spring material to cherry red to shape it
2. Quench in oil
3. Temper to about 700°F

The main questions I have are:

1. Should I heat the spring material to critical temperature and allow it to slow-cool first to normalize it, before reheating it to shape it? Or will heating it to cherry red to shape it normalize it "along the way"? In other words, is normalizing a necessary preliminary step, or will the spring steel be normalized in the process, simply by virtue of being heated above critical temperature?

2. I'm not sure how to temper at this high temperature (assuming it's the correct temperature). The oven doesn't get this hot. Can I put the quenched spring back into the coal forge and keep checking it for color (or with an infrared thermometer) to pull it out when it reaches 700°F ? Also, does the spring need to soak at 700°F for a while, or will it be OK if it just reaches 700° and then comes out of the fire to air cool?

Are there any other big things that I need to do, or think about, that I don't even have the sense yet to ask about?

Thanks in advance for any tips.

[bigfootnampa]

At only 5/32 inch diameter you won't need much soak time to heat through the core... seconds ought to do. If I were doing it I would use the "greasy stick" method to temper. This involves baking gently atop the fire and then checking with a wooden stick... when the stick slides easily along the metal as if it were soapy the heat is reached... stick sticky, not yet hot... stick burning, overheated. This tends to be a bit higher than 700 degrees but about right for spring tempers. If you are only bending the wire in one or two heats I would likely avoid the additional heat for normalizing... this is more needed when making significant changes to the shape of the metal.

[bigfootnampa]

BTW you know, of course, that you could much more easily buy the spring... but I think it's nice that you are choosing to embrace the opportunity to learn and practice instead! I'd keep the heats to make the wire wraps as low as practical, you might get this done at a dark red heat or two... though maybe not at first try. I'd think a mandrel wrap would be the easiest way to do it.

[Rich Hale]

Was any of the information in the heat treat stickies of value to you?

[Crunch]

Thank you Bigfootnampa, that's good to know about the "greasy stick" temperature gauging trick.

Rich, I had not looked at the stickies yet, but thanks for pointing me to it. I read the first linked thread; there's some good info there and I'll read the other two threads, too.