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Robert Simmons

Processing a Coil Spring for Tools

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I thought I would make up a post on processing a coil spring from start to finish for hand tools. As I am a greenhorn, I plan to use this steel to build my tool collection. I need chisels, punches, drifts, you name it. We (my 14 year old son and I) started with two automotive coil springs I got at a scrap yard. I first cut off whole coils then cut coils in half.
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This left us with a ton of half circle rings. Now it was time to heat them. They al had some kind of paint on them so I made sure I had good ventilation and stuffed them al in the forge to heat to yelow.
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We straightened them all on the anvil and then tossed them in my bucket (which is lined with castabe refractory).
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After we had them all in the forge to heat to yellow dso they could anneal. We had to shuffle them a bit but eventually all were yellow.
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Finally we buttoned up the forge tight to let them cool slowly to anneal. With that much metal it should take hours to cool inside the firebrick forge.
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And soon we shall be able to start making tools.

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I use coil spring a lot as it is one of the few decent quality steels I can get here. I don't cut it up, though. I straighten it roughly and leave it as a long bar and make stuff on the end of the bar. That way I don't usually need tongs to hold it which makes working it that much easier.

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Hey Robert,
Thanks for the info on the coil springs. Curious, what size springs were they? Small car, etc. I will take a trip around the farm storage (junk) area and see what I can find.
Good luck with your tools.
Mark<><

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If you want to keep them nice and round and free from hammer dings and flat spots, try heating just a few inches of the end and then squeeze it straight in a smooth-jawed vice...then just keep working your way along until you have a convenient length of bar you can hold on to with your hand. Makes forging points on the end a lot easier if you don't have good tongs to hold the pieces (I know because I don't really have "good" tongs) ;)

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PS. I like your forge. I've never used gas since it really wouldn't work for me in the winter...but it looks easy to close up and even to change the inner dimensions if you need to...just re-stack the bricks and you got a new forge !!

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Robert, you should check out the thread "tools from spring" by Brian Brazeal, he shows some great examples. You'll find it in the tools section.

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Those will also make good knife blanks, there is a thread on forging double tapers by BrianBrazealBlacksmith using a piece of coil about that size for knife making. If you weren't done already, I would suggest leaving some bigger pieces than half coils for projects other than tools. Coil spring makes good dinner bells too, and many other tasks that require hardenability, durability, or a bright sound (compared to mild).

All the same, that is a good start, and I am glad that you did a slow cool step as it makes storage of the metal safer. Fully hardened medium and high carbon steel can just break sitting around, possibly with pieces moving at high speed. An air cool would have worked fine for this purpose.

Burying in fluffy wood ashes is another way to get a good anneal, and will in fact work BETTER than cooling in the hot forge for single items (you still may need to heat an additional piece of stock to bury alongside for longer cooling). For burrying make sure there is at least 2 inches of fluffy wood ash around all parts, especially the ends as they can end up in odd places. A small lidded metal trash can or fireplace ash bucket (about 5 gallon) is suitable for a very large number of projects. Being covered will prevent ash dust from being in the air except when you open the can. there are other materials that can be used instead.

However keep in mind that a full anneal is not required for most purposes, just when you want the metal as soft as possible such as before grinding, after forging preparing for heat treat.

Heating to a bit above non-magnetic is adequate for annealing and normalizing. Heating too much higher can cause grain growth instead of reducing grain size. "Yellow heat" for most of us is significantly above non-magnetic, but everybody's eye sees these colors differently. Calibrating your eye to heat is not easy, as the color looks different in different lighting.

Glad you and your son are enjoying the fire, and getting some quality time together.

Phil

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Coil spring is good tool steel best of all it's pretty forgiving of mistakes in heat treatment.

For instance yellow heat is WAY too hot for annealing or other heat treatment. Non magnetic is bright red, virging on orange. The old "cherry red" is based on the color of cherries a century or more before our current red red cherries.

One way I like for straightening coils if I want long stock and I usually do for ease of handline like Phil suggests is to anchor a rod solidly and heat the entire coil to bright red or low orange. Slip the coil over the anchored rod, post, bar, whatever, grab an end of the coil and pull like crazy and it'll uncoil.

I like vermiculite for annealing but often just leave pieces in my (closed off) forge to cool slowly, this yields something between annealed and normalized results and is just fine for non-specialized needs.

Frosty the Lucky.

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PS. I like your forge. I've never used gas since it really wouldn't work for me in the winter...but it looks easy to close up and even to change the inner dimensions if you need to...just re-stack the bricks and you got a new forge !!



Well getting to that forge, and especially that burner was something of a journey. However, I don't know why it wouldnt work in the winter. I cant imagine even a 50 point drop in ambient shop temperature would affect the forge much given that it is 2000+ degrees inside.

As for the forge, its good but the bricks get a bit fragile when hot. I have broken a few reconfiguring. Frosty has the best variable volume forge in my opinion and I am getting there. However, I would change a couple of things that he did such as the roof. But anyway, it will get there. It works for now.

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I cant imagine even a 50 point drop in ambient shop temperature would affect the forge much given that it is 2000+ degrees inside.



The temperature drop will not directly affect your forge, it will affect your fuel supply. You tank will "freeze" and the liquid inside will drop well below ambient temperature as heat is removed to evaporate the liquid propane in the bottle.

Cures are
bigger bottles - few people with 100# bottles complain about the bottle freezing till they are at the very end

manifolding several bottles - increases surface area of the bottle and propane, and increases heat transfer into the propane

warm water bath - warm water (warm being relative as I use cold tap water) will push more heat into the propane and it will evaporate faster. The benefit is reduced as ice builds on the tank, but works well for sessions of about 1 1/2 hour on a grill bottle.

work in a heated shop with proper ventilation.

Have fun, I have found myself in a snowdrift that was not there before I started.

Phil

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If you want to striaghten those half coils without marks and dings heat them up to forging temp. Then set the ends on the anvil arch up strike on top of the arc as the part you are hitting is not supported you will not forge a hammer mark on the spring. If you put the ends over the edge of the anvil you will get dings on the spring where it contacts the edge of the anvil as it slides over the edge. Dings in the stock can cause stress points and cold shuts in the finished product. This method was taught to me by Clifton Ralph. Of course Clifton used a long heavy piece of leaf spring over the bottom die and did it on a power hammer.

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As for the forge, its good but the bricks get a bit fragile when hot. I have broken a few reconfiguring. Frosty has the best variable volume forge in my opinion and I am getting there. However, I would change a couple of things that he did such as the roof. But anyway, it will get there. It works for now.


Check out Ralph Sproul's variable volume forge near the bottom of the page. http://www.bearhillblacksmith.com/

Frosty the Lucky.

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I have used the pritchell and hardy holes to take the bend out of a half coil of auto/truck spring, then finalize the straightening on the anvil face.

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I cant imagine even a 50 point drop in ambient shop temperature would affect the forge much given that it is 2000+ degrees inside.

Like Phil said, it's the fuel that wouldn't work for me...my "shop" is not insulated, and though I do have a wood stove, it would take too long to warm up propane tanks as opposed to throwing the charcoal into the forge

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