Teller
Canyon
Forge
Teller
Canyon
Forge
Forging, Heat Treatment, and Finishing
Contents
Hand-forged to Nearly Finished
Forge Fuel
Finishing
Heat Treatment
Heat Treatment for 5160 and 52100 Blades
Heat Treatment for Straight/Plain-Carbon Steel Blades
Some Thoughts on Finish for the Blade and Fittings
Handle Materials
Construction
Concessions to Modernity
Quality Assurance and Testing
All of the knives we make are hand-forged from new steel. Most of the non-damascus knives are made from new 5160 Grade H barstock or new E52100 round stock. You can read more about the rationale behind our choices in steel and blade design in Our Thoughts on Knives and Steel.
The primary reason for forging steel, whether knives or rifle receivers, is to orient the grain structure of the steel to the shape of the product. Multiple normalizations following forging and finishing operations greatly reduce the grain size. Correct grain orientation and small grain size give the steel much greater shock strength which results not just in toughness of the body of the blade but also in better edge retention and a greatly lessened tendency of the edge to chip.
To satisfy the absolutists, yes, the strongest possible blade would consist of a single grain. However, given that we live in the real world where, at least at the moment, no-one knows how to do that and given the fact that the grain boundaries are weaker than the grains, the best achievable result is a structure consisting of very small grains. That's because any stress imposed on the steel is then distributed over more of the weaker grain boundaries. Furthermore, some alloying elements, like chromium and nickel, impart some lubricity to the grain boundaries, further increasing the toughness of the steel.
Hot-rolled barstock has a structure consisting of relatively large grains in a pattern which is oriented generally parallel to the long axis of the bar. The forging process orients the overall grain pattern to the geometry of the blade. Obviously, it's not possible to achieve this purely by stock reduction which simply cuts across the grain pattern of the steel. A forged blade can be finished by grinding or filing without disturbing the "forged-in" grain orientation provided that the blade was forged to its final geometry prior to finishing. Everything we do to a blade with either files or abrasives after forging is a finishing operation. The three-dimensional shape of the blade is 100% complete when it comes off the anvil.
We make hand-forged knives from new steel bar or round stock to finished condition with minimal stock reduction. The only place we do anything that could legitimately be referred to as stock reduction is at the blade-tang transition. There are, in general, two ways to handle this. The traditional smithing method is to set the tang down over the edge of the anvil. This works but can have an undesirable effect on the grain flow at the base of the blade (the blade-tang transition). Instead of doing it this way we usually file or grind most or all of the the blade-tang transition (shoulder(s)) after forging.
We started out using coal but were never satisfied with the results. This was due in part to the fact that good forge coal is hard to find here and clinker was a real problem. Coal also burns hotter than is needed for forging blades. Most importantly, when forging very close a large number of heats are needed and it's difficult to keep a reducing fire all of the time with coal. The result was that we almost always saw some (at least surface) decarburization of the steel. We were well and truly unpleased.
We then switched to charcoal for forge fuel. Tim Lively convinced us that charcoal is a very good forge fuel for bladesmithing, and he was right. We've found that with it we've had very little decarburization and essentially no pitting even when forging a blade takes as much as 12-24 hours. There are at least two factors at work here. It's easier to maintain a reducing fire with charcoal and charcoal doesn't generate as much heat as coal. A welcome additional benefit is that the amount of harmful impurities present in charcoal is much less than in coal (especially the coal available around here).
Not just any charcoal will do for this purpose. Your basic barbecue briquettes contain a binding agent, usually clay, making them undesirable as a forge fuel. The less-expensive charcoal briquettes are actually mostly coal dust and clay binder, making them the consumer's best choice in bad coal. We make our own charcoal in 20-30 gallon batches from deadfall and scrounged dimensional lumber scraps using a retort based on a design by Daniel O'Connor.
If you're interested, for whatever reason, in making charcoal you should remember that there are some kinds of wood that you shouldn't use. Treated lumber has stuff intended to kill fungus and bugs in it that you definitely don't want in your charcoal. Arsenic, frequently present in treated lumber, is poisonous. Another one is wood that contains a significant amount of silica. Osage Orange and some others manage somehow or other to incorporate what amounts to sand in them. If you make charcoal from them you can get clinker (molten rock) in the fire when the charcoal is burned in a forge.
From our point of view, finishing begins with the forging of the blade. Forging the blade and tang as close to finished condition as possible results in less filing being required prior to polishing. In general removing irregularities in the surfaces is done better and more rapidly by forging than by filing. Still, most of the actual time spent making a knife is in the finishing process.
Any residual irregularity in the profile and (usually all) hammermarks are removed by draw-filing and/or grinding. The blade is then hand polished using stones to at least 220-grit. Final finishing and polishing are done, by hand, with stones and various other abrasives following heat treatment.
Obviously, the heat treatment procedure required is dependent on the type of steel used. We've chosen to use (almost exclusively) two steels (see Our Thoughts on Knives and Steel) for which the heat treatment procedure is essentially the same. In any case the goal is to retain the grain orientation achieved during forging and to reduce the grain size while hardening the cutting edge(s) and keeping or rendering the remainder of the blade and tang springier and stronger/tougher.
The heat treatment process we follow produces a blade with a consistently small grain size, that has a hard edge and is tough and springy everywhere else.
Heat treatment actually begins during forging by careful heat-cycling of the steel and forging with reduced heats after initial shaping.
After forging and finishing operations on the blade are complete the blade is normalized at least three times to relieve induced stress and to reduce the grain size.
Most of the blades we make are differentially hardened by edge quenching (see Quenching Methods and Steels) three times in heated oil, with the blade being allowed to cool in the oil overnight each time. The interval between quenches is no less than 24 hours. The hardened portion of the blade is then reduced to working edge-hardness by tempering in three one to two-hour cycles depending on the thickness of the blade and cooling to room temperature after each cycle. Between the second and third tempering cycles the blade is cooled to -20F and held at that temperature for 24 hours. The sub-zero cooling is needed because for steels containing greater than 0.5% chromium the martensite final temperature (from metastable/retained austenite) is below room temperature. It takes nearly a week of elapsed time to heat treat a blade this way but it pays off in the finished knife's performance.
Most of the information above concerning 5160 and 52100 applies to 1095/1084/1075 (see Steel Information), as well. The only substantial difference is that straight carbon steel does not benefit from multiple quenches or from sub-zero chilling following quenching (the martensite final temperature is above what most of us would think of as room temperature). These steels are quenched once and then tempered three times, being allowed to cool to room temperature each time
We'll polish blades to whatever degree the buyer wants, but some things should be kept in mind when making the decision. First, a mirror finish on a blade tends to show marks from use. Notably, an edge-quenched blade is relatively soft at the spine and is, in general, a bit more prone to picking up scratches above the quench line because the steel above there is progressively softer in the direction of the spine.
Having said that, we prefer at least a 600-800-grit (often 2000-2500-grit) finish with all fire-scale and irregularities in the surface removed on hunting and kitchen knives because it's easier to clean them thoroughly if they are really smooth. We don't like to leave any fire scale on hunting or kitchen knives because stuff can get under the scale and stay there. This is good news for preservation but bad news if you're concerned about bacteria.
It's worth noting that if you don't put the knife in its sheath dirty the only scratches it will get are from contact with whatever you're cutting with it. It will get scratched, though, even on the really hard portions of the blade; it's just a fact of life if you actually use a knife.
We can, of course, leave the blade hammer-marked everywhere which, if you like the look, results in a blade that doesn't show marks from use to any great extent. On the other hand, if you don't like the look of a hammer-finished blade you might say that it simply doesn't look any worse after use.
That's our 2-cents worth on level of finish. The level of finish on your knife is up to you.
Here in Colorado, stabilization of tight-grained hardwoods isn't really necessary provided that they are sealed well. We frequently just use tung oil. Of course, that means that the wood needs some care just like the blade (see Knife Care). We'll use stabilized wood if the customer wants it and in general, will use almost anything the customer wants other than shell and stone for handle materials.
Most of our knives are made with a through-tang design. Our through-tang knives are not "stick-tang" knives. The tangs on them are nearly the width of the blade at the front, tapering to 1/4 inch to 1/2 inch at the rear depending on the size of the knife; as the term implies, the tangs go all the way through the handle and pommel or buttcap. The tang is peined over the pommel or buttcap. This type of construction, using Acraglas Gel® to further secure and seal all of the parts, results in a very strong handle that simply will not loosen. In fact, the only way to get a handle made in this manner off the knife is to grind it off.
We take a pragmatic approach to most things. For example, producing the "look" and performance we like in a knife quite naturally results in the choice of the hand-forged method rather than stock removal. While we prefer traditional means of production and produce very good results with them, there are some cases where hand work adds nothing other than expense and time. In these cases we simply use the best tools and materials for the job. In short, we use power tools where they make the job easier or faster without compromising our commitment to hand-work.
We use Acraglas Gel® (which was designed as a rifle-bedding compound) to attach and inside-fill wood, bone, antler, and other handle materials. It contains nylon fibers, is much stronger than plain epoxy and won't crystalize and fracture like plain epoxies, produces a very strong handle-to-tang bond, and is thoroughly waterproof. If pins are used they are radially grooved to give the epoxy something to grip and are not peined or riveted. Peined or riveted pins simply aren't necessary and impose stress on the handle material which can result in eventual cracking and/or splitting. In any event, pins are really just "insurance" because the epoxy bond between the handle materials and the tang is very strong. On full-tang knives we always drill some extra holes in the tang so that pins-or-not the epoxy bonds the scales to one another as well as the tang.
We also use new steel because that can yield better, more accurate heat treating results since we know exactly what the steel is. We actually do use scrounged/junkyard steel for making some tools that we use in the shop but, let's face it, the tools we use don't get used as hard as do the knives we make relative to their structural cross-sections. Smithing tools are built much heavier than knives. The quality of the steel in them usually isn't as important.
Every blade we make is tested prior to final finishing and knife construction.
Every 5160 blade we make is tested for overall durability and toughness by bending and checking for correct return to straightness without showing any signs of chipping or cracking of the edge. With larger knives 2 inches of the blade is clamped in a vise and Ken leans his whole 180 pounds on it. The blade is expected to return to straight afterwards. We don't bend them with a cheater bar because we're testing for real-world use and we definitely do not recommend that you stick a pipe on the handle of your knife and use it as a pry bar. Get an actual pry-bar for that; they're much less expensive than our knives. You also shouldn't try to pry knots out of lumber (why do people do that?) with small knives which are usually edge-hard over a larger portion of the blade and thin enough that you'll likely snap the point right off.
Edge hardness is checked using Wayne Goddard's "brass rod test" where the sharpened edge is flexed over a brass rod and then checked for bending or chipping.
On large knives having a markedly convex edge we place a 1/4 inch mild steel rod on the edge and give it a whack or two with a hammer. The edge must not chip or dent. The steel rod must be notched by the blade.
We test the edge retention of the blade. The only reasonable way to assess this is to cut stuff with the blade. With big camp and bowie knives we usually chop up pine 2x4 and/or pine, fir and scrub-oak limbs or splits concentrating on the hard spots (knots) in the material. With other knives we cut up leather scraps and/or cardboard or rope. What we do in this test is more by feel and experience than by science. The point of the test isn't to cut stuff with the knife until it's too dull to continue. We know what we expect of a knife's edge-holding ability and it doesn't take a great lot of stuff getting cut up to see how the edge responds to use. To be acceptable the edge must not show any sign of chipping and the knife must still make nice clean cuts in paper using the dullest portion of the edge after the test cuts.
If Ellen (who is even pickier than I am) finds something she doesn't like about fit or finish of the completed knife, it doesn't go out the door until it's fixed or another one that does pass muster is made.
Finally, we want you to be happy with a knife you buy from us, so if you find something you don't like about it when it gets to you, let us know about it and we'll make it right.
page last modified Sat, 19 Jul 2003 17:58:00 -0700 (MST);
Copyright© 2001-2004 Kenneth L. Smith and Ellen Van Landingham, All rights reserved. Teller Canyon Forge, Teller Canyon Knives, TellerCanyon.com, and the Teller Canyon Forge Logo and Touchmark are the trademark property of Kenneth L. Smith and Ellen Van Landingham.