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Monday, April 7, 2014

Guest Post: An Introduction to Blacksmithing

An Introduction to Blacksmithing 
by Firehand

(Editor's note: Firehand is a blogger and a part-time blacksmith.)


As our hostess was thinking of "In the event of disaster', I'm going to lay out a bunch of information on the subject of blacksmithing/metalworking to cover as many bases as can in one piece. If you get interested, you can start collecting tools to mess with, and in an emergency can look around at what's available and how it can be used. So here goes:

The Basics

When you say 'blacksmithing', most people nowadays think of shoeing horses; not many think of the other things. A farrier is a specialist in making/modifying/fitting shoes on horses and other draft animals; a blacksmith is a generalist.

There are really only a few things you can do to metal with just a fire, hammer and anvil:
  • Stretch a piece out longer and thinner
  • Compress a piece shorter and thicker
  • Bend
  • Straighten
  • Cut
  • Weld
  • Rivet
The thing is, with just those steps you can make or repair all kinds of things. For centuries, every piece of ironwork in the world was made by those steps. 

Some of this stuff gets specialized (blades, welding), but there are a lot of repairs/builds you can do without spending years learning how. A rivet is just a piece shaped with a head on one end and a shaft to fit through a hole; put it through the two(or more) pieces, put the head on the anvil or something else solid enough, and use a hammer to peen out the other end of the shaft. Put emphasis on expanding the end into another head, it'll hold the pieces together while allowing the pieces joined to pivot; hammer more straight down on the end, you expand the shaft to fill the holes completely and help lock the pieces together, then shape out the head to make sure nothing can slip off. You can take a piece of metal that broke(at a weld or just cracked) and fit a piece across the break and rivet it on; won't be as solid as welding, but can be done in places/on things were you can't weld.

Have a piece you need to bolt together, but it's someplace where it cannot be allowed to loosen up? Tighten it down, cut the bolt off just a little past the nut, then use the hammer to peen the edges of the bolt out and down: you can rivet the end this way and the ONLY way it'll come off is if you cut the nut off. Or have a couple of really big wrenches for leverage.


Making Things

Let's say there's been some kind of disaster and you're cut off for a while, and things need making or repair. Some of the things you can do with basic tools and some knowledge:
  • Rivet
  • Make springs, both coil and leaf
  • Make tools(chisels, punches, wrenches, etc.)
  • Heat-treat parts
  • Shape
  • Cut things apart for stock

Things you'll not want to try without some experience:
  • Welding
  • Heat-treating on some of the high-alloy steels
  • Shoeing a horse (Specialty knowledge, and there's the chance of getting bitten, kicked or stomped)

Speaking of Steel

At its most basic, steel is iron with a tiny amount of carbon added. The carbon changes the structure and makes the alloy tougher and harder. Mild steel runs from about 0.05 to 0.3% carbon(yes, that's five hundredths to three-tenths of one percent; doesn't take much). Rebar and lots of general-use steel fits here.

Medium-carbon runs from 0.3 to 0.6% carbon, and can be heat-treated for toughness and/or hardness. The upper range of that includes some extremely useful stuff: most leaf and coil springs in cars and trucks are a 0.6% spring steel, and will make good knives, machetes, swords and axes, as well as springs.

High-carbon runs(without getting into esoteric stuff) 0.6 to a fraction over 1%. Fine knives and other cutting tools are made from this stuff.

The short and dirty of it: the more carbon there is in a steel, not only can it be hardened by heating to the proper temperature and quenching in water or oil, but the higher carbon content increases the wear resistance of the steel. And that is literal; it's not only harder to file or hone, but to hammer as well. Any medium- or high-carbon steel you find now has other elements in the alloy to give if other properties, but I'll not get into that.


Basic tools

Any good hammer can be used, but a double-face(sledge) is best as the basic hammer. Better yet (if you can buy/find/make them) is a double-face and a cross-peen, or straight-peen and a ball-peen, if you're going to do much of this.

The 'peen' is the end opposite the round face. 

A straight-peen is narrowed down to a face parallel to the handle, 



a cross-peen is at right-angle to the handle, 



and a ball peen is exactly that. 



Those faces can help you shape metal in different ways; for instance, use the ball to spread and shape the head of a rivet.

Hammers come in every size from 2 ounces to multiple pounds, brass or steel. And lead; a lead hammer will let you straighten something with sharp corners or some other needed shape without dinging up the shape(use a stump or something for the anvil here).


Anvil

These come in all sizes from "small craft" for setting rivets in leatherwork, to massive multi-hundred-pound monsters. You can also use a section of railroad rail, which works rather nicely. Basically, ANYTHING big and solid enough will work, especially in a pinch.

Tongs

For a working smith, these can come in dozens of sizes and jaw shapes. I mean dozens literally, I've seen the shop of a guy who specialized in decorative work, he had something like two dozen, with jaws shaped to hold square stock, round stock, flat stock, all of different sizes. I should note that he had almost as many hammers, many with specific face shapes for making specific things.


This is a pair I made for holding small round, square and hex stock

For round stock you really need tongs; trying to hold onto the stuff with pliers sucks. If you have some big pliers you could file or drill to cut the jaws to work, haven't tried it personally but have heard it works.

Forge

To forge, you need heat. For that you use a forge. All kinds of choices: burning coal or charcoal, gas-fired, electric. In a pinch you can build a fire in a grill and use some kind of blower to get the forced-draft of air that gives the heat you need.

My first forge was made from a brake drum (cast iron is wonderful for the purpose). Later that drum was put into a rectangular cast-iron sink; drilled holes and cut to make a hole near one end, set the drum in as a firepot.

You can use a small round charcoal grill: line it with clay(fireclay from a fireplace shop is best) to keep it from burning out, cut a hole in the center, use some pipe to bring the air in and a piece of heavy grill or steel with a bunch of holes drilled in for a grate to keep the fuel from falling through.

Blower

For years I had a squirrel-cage blower from an old copier, with a ceiling fan speed control wired in. You can find hand-crank blowers at flea markets or antique shows. You can use a large fireplace bellows, or build a BIG bellows if you're making a serious shop. Long as it'll pump air into the fire in a controlled way, it'll work.


General rules

Try to work high-carbon steel when it's cooled down too far, and it can crack; best to keep it and medium-carbon at a nice medium red, re-heating as needed.

Heating

Get steel too hot - above about 1600 degrees F- and it causes the grain structure to enlarge; that actually weakens the piece. You can repair that by heating it to low-red and letting it cool slowly, repeated several times. You can also work it a couple of heats at low-medium red with lots of light hammer blows, which helps refine the structure.

Any steel you can successfully work and heat-treat with a basic forge hardens by getting it - or the section you want to harden - up to 1450-1550 F, then quenching it. Lower than that, it won't fully harden; hotter and you can wind up with the enlarged-grain problem.

That heat, in color, is often described as a cherry red, but I found something that worked better for me, but you'll have to experiment to actually see it. Take a piece of steel of small size - no more than 1/4" thick, better about 1/8" - and a propane torch. Start heating the piece with the flame directed at a point about 1/2" back from the end, shifting it back & forth just a bit so it heats a wider area, and watch. As it hits about 1000 F you'll start to see a visible heat glow, and as the temperature rises it'll get brighter. You'll notice - at the risk of sounding poetic - a shadow inside the steel, inside the red; as the heat rises the shadow will get fainter and fainter, and right at critical temperature the shadow disappears. That is the point at which you'd quench it to harden. May take some practice to see it, but it works.

Quenching

For quenching, I'd suggest oil. Some low-medium steel may require water, or a BIG piece might, but for smaller stuff - blades, punches, chisels, springs - light oil is better, and better if you heat it up to around 100 F first. Oil is a 'slower' quench than water, but also causes less shock to the piece, and if the oil is hot it flows better, carrying heat away more evenly. There is also less chance of a long and/or thin piece warping.

Heat Treating 

With most steels you might work with, heat-treating is a two-step process. Hardening is done by the quench; it freezes the structure of the piece in a highly-stressed state, with high-carbon steel so stressed that it can crack or shatter if dropped on a hard surface. The second step is tempering: heating the piece up to a lower temperature so as to achieve a balance, relieving enough of the stress that it's not brittle - still hard enough to hold an edge in use for cutting tools, and for springs to make them hard/springy enough to do the job, yet not so soft that it'll bend. Tempering over a heat source by eye is done by the colors that appear on the surface as it heats.

Tempering

To temper by color, you have to take the hardened piece, wipe off the oil, sand the surface to clean it and make it shiny - as shiny as you can, so you can see the colors as well as possible.

As to those colors:  take a piece of shiny carbon steel and start heating one end with a torch, and watch the surface. You'll soon see colors appear: first a very pale yellow, then as the heat soaks in and moves down the piece you'll see the yellow moving and being replaced by darker yellow, then a bronze, then pale purple/blue, then darker blue and if you keep heating you'll see the last becoming a grey. In tempering, pale yellow is the hardest, purple in the middle, dark blue/grey softest. 

 Which you want depends on the steel and the intended purpose:
  • A knife/blade that has to stay sharp as long as possible and won't be subjected to stresses other than cutting might get away with being a pale/medium yellow
  • For general use blades, dark yellow/bronze is better
  • Machetes should be more into the  purple range
  • Springs need to be a purple/blue 
Remember, this coloration depends on the type of steel as well as its intended use! 

Getting this done by hand over a fire is tricky; a lot of people have used either pieces of iron pipe split lengthwise set over the fire (it gets really hot, and you work the back of the blade along it to slowly soak up heat), or something like a die can be laid on a flat plate heated from below. I've also seen a large block of iron/steel heated to a low red and then the back of the blade held on it. Slide the steel back & forth to make sure it heats evenly, and watch the colors; when the color you want reaches the edge, or the spring reaches blue, quench it in the hot oil to stop the process, then let it cool COMPLETELY before anything else.

The above is why I temper most knives in the oven: clean it, shine it, put it in the oven at about 375 F and let it sit for about an hour (longer for a heavy piece, it has to heat up all the way through). Take it out and check the color, if it's not there yet up the temp about 25 F, shine it back up and put it back in for another hour. Whatever process you use, be aware that if you overheat it the only fix it to harden it again and start the tempering process over.

Small springs, especially coil, can often be made without hardening/tempering. Hobby shops and some hardware stores carry music wire in different diameters in 3-foot lengths. Very good stuff with lots of uses, including winding it around something ('mandrel' is the correct term) to make a coil spring. If it's small enough diameter you can do it without heat, but be careful: this stuff is springy, and you're putting real tension on it, and if the end gets loose and whips around it can do you damage.

Resources

That's it for this piece,  a basic run-down of some things on smithing. I realize there are holes, and a LOT more that could be covered, but if I tried to fill in and cover it all this would be a book. If there is interest, I would be willing to write more articles. 

I do want to throw in some places to get tools/materials, so here goes:

Steel

Salvage yards are your friend. Coil and leaf springs, mild steel, all kinds of stuff.
Industrial supply and machine-shop supply will have lots of stuff. One of the online places is Enco. They carry tools and materials,  including oil-hardening and water-hardening drill rods in different diameters. The oil-hardening is usually O-1 tool steel, which makes very good knives. They also have brass and aluminum stock, bearing stock, lots of stuff.

Hardware and hobby stores for music wire and some other things.

Metal Supermarket has a lot of stuff, including brass, in many shapes and sizes.

Tools and sources

If you can afford to buy the stuff new,  Centaur Forge has damn near everything smithing- and farrier-related: tools, materials, forges, anvils, coal, vises. Be aware that the prices on some of it may put you in shock: new anvils are SPENDY, same for a post vise.

Don't forget to check places like local tool store. There's one in Oklahoma called Steve's Wholesale that has hammers and drill bits and chisels and hacksaws/blades, all the usual stuff, and sometimes has anvils as well. The anvils are usually made in China, but can be had for a LOT less than one imported from Europe, and last I heard a new anvil WILL be imported as nobody in North America makes them.

If the anvil is from China, or you find one at a flea market or farm sale, test the face to make sure it's hardened. If it's not, it'll wear badly in use. The test is simple: hold a hammer you know is good a few inches above the face and let it drop. If the face is hardened it'll bounce, if it's not it'll go 'clunk' and sit there. Be aware that not every good anvil rings, so trust the bounce.

Ball peen and cross-peen hammers aren't hard to find, straight-peen you'll have to either buy or take a two-face hammer and modify one side; that's what I did for my two-pound and four-pound cross-peen.

Actual tongs, you'll either buy from someplace like Centaur or at a flea market or farm sale, or make. Yes, you can use big pliers and vise-grips, but for some things tongs that properly fit are wonderful things.

Books

And let us not forget books. Lots of them out there nowadays, some of the good ones are:

Wayne Goddard's $50 Knife Shop

The Complete Bladesmith

Country Blacksmithing  (This one's out of print. If you can't find a copy, quite possibly the library can get one in; it's a good general smithing book.)

The Complete Modern Blacksmith

These are just a few of what's available; check the library, quite possibly they've got some available.



The Fine Print


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