By Matthew ParkinsonDownload Tutorial
Dealing with Medium and High carbon steels
When making a knife or any edged tool a high or medium carbon steel is needed. This kind of alloy is also called “spring steel” or “tool steel”. When working with these steels the higher the carbon content and the higher the alloying content the more sensitive the steel will be to working in the correct temperature ranges. Some of these alloys can be red hard (a temperature range that the steel is hard to work) or red short (a temperature range that the steel is prone to cracking or crumbling) generally these problems are more common in high alloy steels, simple high carbon steels tend less to these problems but will develop large grain size if held at high temperature. Large grain size weakens the steel, is detrimental to the cutting ability of the finished knife or tool.
The best way to avoid damaging the steel you are working with is to know what alloy you are working with. Look that alloy up on line, or in one of the many reference books. Find out what that alloy is prone to, (if it is red short or red hard) what the hardening and temper ranges are. (you will need this info later) how ever with all of these alloys there are a few things that should be done. First Do not soak the steel in the forge, second do not heat the steel to a higher temperature than is necessary to work it, and third as you forge closer to finished shape work at progressively cooler . temperature And finally normalize the steel before finishing the knife (filing grinding etc) to normalize heat the steel to critical temp, this temp can be found by using a magnet to find the curire point,(the point that heated steel turns nonmagnetic) critical temp is a few hundred deg. Higher than the curie point. Heat to critical and let cool in still air to about 400 deg F.(the temp that the steel regains magnetism is generally sufficient), do this three times ( or cycles) this will reduce the grain size break down any carbides that might have formed, and soften the steel making the grinding/filing easier.
In the USA Steel alloys are graded using two main systems, the first is a numeric based system (SAE, AISI) in this system there are 4 or 5 digits that determine the alloy, the first two determine the alloy content and the last two or three the carbon content, these are called points, 100 points equals 1 percent by weight of carbon so 1050 steel would be a simple carbon steel (10=simple carbon steel) with .50% carbon content. The minimum carbon content to make a good knife is about 40 points (.40%) and the maximum is around 1%.
The second grading system is the letter number system of tool steels, theses are specialty alloys that were developed for a purpose so with in one set of steels (O series for example) there can be a total change of alloys with similar fished properties. Some of the more common steels in this system are O1,W1,W2 ,L6,S7 and D2. Most of these steels can make vary good knives but some can also be very difficult to work.
One of the most intimidating things and the greatest fear for any new smith is forge welding. Welding in this context is actuality rather easy; so long as a few simple conditions are met the weld will take.
First what is a forge weld? A forge weld is a solid state weld, which is to say that no part of the metal becomes liquid at any time in the process. In the solid state metals exist in a form where the nuclei arrange themselves in an orderly grid and the electrons are shared as an “electron sea”. This is why metals make good conductors of both heat and electricity. In the case of forge welding, the weld is formed when the two pieces of steel are brought close enough to begin easily passing electrons back and forth, in essence becoming one piece. As part of this process alloying elements may also diffuse across the weld boundary, slowly homogenizing the steel. Some elements, such as Carbon, move relatively quickly, while others, such as Chromium, move much more slowly. The differences in alloying elements between the two materials are what cause the pattern to be visible when etched in Damascus
To form a successful weld it can be thought of that three conditions must be met. The first condition that must be met is a perfectly clean pair of surfaces. By this I mean that there can be NO oxides present in the weld zone and no foreign matter to become trapped in the weld. The second condition is an inert atmosphere around the weld; this prevents any oxides from forming during the process, since these would prevent the electrons from easily crossing the boundary. The third condition is proximity: the two surfaces of the weld must be brought into close contact since this encourages the electrons to cross the boundary and a metallic bond to form. Heat is not necessary but can help to create the conditions necessary to make the weld. Higher temperatures mean greater energies, and at higher energies it is easier for the electrons to jump the boundary. Iron oxide actually melts at a lower temperature than iron itself, so higher temperatures can help an oxides on the surface to flow away. Lastly, higher temperatures mean softer materials, and softer materials make it easier to forge the surfaces into the atomically close contact necessary for the metallic bond to form.
Creating the necessary conditions can be accomplished in more than one way. The classic method is the flux weld; in this method a flux (most often Borax) is used to break down the surface oxides at high temperatures (meeting the first condition) and forming a glassy film sealing the surface,(creating a inert atmosphere and meeting condition two) the flux is then forced out of the joint when the hammer blow presses the two surfaces together (bringing the two surfaces into close proximity and meeting condition three). The down side of this method is the likelihood of trapping flux in the joint; even on the very best flux welds, flux can be seen in the joint on a microscopic level. Due to these inclusions, flux welds work best and are strongest when they are drawn out to at least twice the original length. This refines the weld and distributes any possible inclusions over a greater area.
A more modern method is the Box weld. In this method the plates to be welded are cleaned of scale and oxides by grinding the surfaces clean. They are then stacked and tacked on the corners with an electric welder. They are then soaked in Kerosene and a sheet metal box is built around the stack. The box is sealed with some of the kerosene inside and a small pinhole is left open in one end. The box is heated in the forge, burning off the kerosene and creating a reducing atmosphere inside the can. Once heated through the billet is then compressed to set the welds. The first two conditions are met by the burning of the kerosene. This creates a very reducing atmosphere in which no oxides can form and existing iron oxides are reduced to pure iron. The atmosphere will stay a reducing atmosphere until such time as the billet is cooled, so this meets the first two conditions and the compressing of the billet to set the weld meets the third. The down side of this method is that it limits the size and shape of the welds along with the work that it takes to form a box for each re-stack. On the other hand this method will form a much more solid weld with NO possibility of anything trapped in the welds. This method is really only viable with access to a hydraulic press as the entirety of the welds must be set at once. This method works especially well with hard to weld alloys like stainless steels and for oddly shaped welds as in mosaics.
A very new method of welding is the Oil weld or Kero weld. In this method the forge is run up to welding temp and adjusted to run rich creating a reducing atmosphere. The plates to be welded are stacked and tack welded on the corners. The billet is then soaked in oil or Kerosene. The billet is heated and soaked at welding temp for 1-2 mins (after reaching welding temp) and the billet is then run under a power hammer or hydraulic press to set the welds. This method works under the same chemistry as the box weld except it uses the atmosphere of the forge and the burning oil to create the heavily reducing atmosphere needed to reduce the oxides and clean the surfaces. This method seems to work best if a power hammer or press is available, giving clean, strong welds without the extra work of a box weld. A related method, the so call “bareback” weld, uses the a reducing atmosphere in the forge and long soak times at welding temperature to break down the oxides. This method works surprisingly well and produces exceptionally clean and strong welds. It can lead to strong decarb along the weld lines due to the carbon in the steel being removed to bond to the oxygen from the oxides and form CO2 . Some testing has also shown minor oxide inclusions at the edges of the billet in both the Kero and “bareback” welds, but most smiths consider the small inclusions to be a minimal drawback in comparison to the many advantages of these welding methods
What ever method you choose to use should be based first on your available equipment and second on your material choices. For example, I have had less than perfect results welding wrought steels and iron with any of the flux-less methods, possibly due to the silica slag that is inherent to these materials. As with other aspects of knifemaking, read every thing you can on the subject; understanding how it is working can go a long way to helping diagnose problems when it stops working.
The flux weld in practice
To begin prepare the billet to be welded by assembling and tightly clamping wiring it together if necessary.
To flux weld,The billet should be heated to a dull red heat removed from the forge and fluxed, placed it back in the forge and take the billet to a welding heat (a bright yellow almost white heat, about 2200 deg F) remove the billet and use a wire brush to remove the spent flux, reflux and replace the billet in the forge. Once the billet is back to a welding temp, set the welds on the anvil with firm blows of the hammer, begin at one end and overlap your blows setting the welds along the length of the billet. Wire brush the spent flux off and repeat to be sure the welds are solid. The welds can also be set using a hydraulic press rather than a hand or power hammer. With a press it is best if the whole of the weld can be set under the dies at one time. Squeeze down until you see the flux run out the sides.
Look for dark spot or lines dividing a hot and cooler section this indicates that a weld didn’t take, reheat flux and reweld that section. The welds can also be set under a power hammer, this is helpful with larger billets, but is unnecessary with the smaller starting billets.
Once welded the billet can be draw out by hand, with the help of striker, or with the help of a power hammer/ forging press. How the bar is draw out is irrelevant, it is how ever of the utmost importance the all forging is done parallel or perpendicular to the welds for as long as possible, if the bar is forged at an angle it will place undue stress on the welds and can lead to the weld sheering and in the case of steeled edges or San Mai shift the steed edge off center. Adjust any angled forging as soon as it is noticed before the weld sheers. Work the billet only above a orange heat to place as little stress as possible on the welds.
For a Oil or bare back weld set the forge to a high heat and a reducing atmosphere (slightly gas rich) I prefer to clean the steel by grinding before hand. Place the billet in the forge and bring it up to a welding heat, soak it at temp for 2-3 min then set the welds under a power hammer or press. This works best is the whole of the weld is set at once so use a long set of press dies or go across the wide side of the power hammer dies. Once set the billet can be drawn out as normal. This type of welding produces from the start a very strong weld much less care needs to be take when drawing. There is a slight tendency not to weld at the very edge of of the billet. This is for the most part superficial and easily removed by grinding, if present it should be removes as the billet is prepared for twisting.
beginning with a piece of wrought 7-10” long and around 3/4” square. Reforge the material to this approximate size if it is not available. Cut a slit down one face about 6” long and half way through the material with a chisel. Forge a piece of High carbon stock (1095 W1 1084 etc) to approximately 5/16 /1/2” and beveled to the center along one side.
With the wrought hot insert the steel, and forge the wrought to a close fit around the steel. Flux and take a welding heat. Heat with the steel up and bring every thing up slowly to temp. Weld with a downward strike with the steel edge up first to set the weld then work the two sides to finish the weld. flux and reheat as needed. Using welding heats forge the billet down to 1/4” thick with as much width as possible and keeping the steeled edge centered along one edge. Trim off an approximately 2” long section at a 45deg angle. Forge a loop on the cut edge by setting a shoulder and drawing out the stock. Then scrolling back to form the loop. Repeat on opposing side. Use a chisel to lightly score the steel edge.
Harden in oil with out normalizing, fire strikers work best with large grain. Cool to room temp and wet boil water off the surface 2x to prevent cracking to finish.
Forging the Trade knife
Using the remainder of the billet. Forge material to approximately 3/16” thick. Use a half face blow to set in the tang. Set the tang in just into the steeled edge. Trim off leaving around 1” -1 1/2” of material for the tang and forge out tang. The tang should taper from blade side back and remain 3/4”–5/8” wide.
Forging the shape
Begin by deburring the end of the bar from trimmed end. Now take a heat on the point of the bar,( a forging heat is a yellow heat) set the end of the bar on the far edge of the anvil and hammer the top corner back into the bar. Every other heat forge the thickness back in line with the parent bar. By rotating 90DEG and hammering the flats (work both sides of the flats)
Forging in the point in this way avoids fish mouth. ( the end of the bar folding over it’s self, forming a crack) when working with off size stock forging a point as you would in square stock will lead to fish mouth. As the center of the bar will not move as fast as the out side. If the bar was trimmed at 45deg this should go very quickly. Just be sure that the LONG edge is the one with the steel in it! Once the bar has been taken to a point begin refining the shape of the profile into the perform of the blade shape. Take care as you forge in the shape that the flats do not get wider than the parent bar and that the bar stays flat.
Once the shape is forged in taper the thickness (distal taper) the point of the blade should be about 1/8”or a little under, and taper to the parent bar thickness at the hilt side of the blade. To taper the blade take a forging heat, and forge the point down to about 1/8” then work back toward the hilt tapering the flats, re forge the profile as needed.
Forging in bevels
Begin forging in the bevels at point of tang, to do this angle the cutting edge side of the blade on the anvil and strike at this same angle, strike as near to the edge as possible and once a bevel is established shallow out the angles and begin working higher up on the blade to shift the bevel up the side of the blade until it reaches the spine. If leaving a ricasso pinch out the beginning of the bevel by hammering inline with the edge of the anvil and drawing out the edge. Once pinched in the ricasso should NEVER be on the anvil when forging the bevels in.
Because the edge is expanding as it is forged thinner, the blade will curve away from the edge. Correct this at the end of each heat, when the blade is still in the reds by setting the spine of the knife on the anvil and firmly hammering the edge back to straight .As the bevels are forged in be sure to work both sides evenly. Flip the blade over and work the other side keeping the same angle used on the first. It is best to work both sides in the same heat, but if this proves difficult a workable option is to alternate side to side from one heat to the next. As the bevels are forged in concentrate on keeping the edge centered the bevels even and of an even thickness , forge the bevels to a thickness about that of a dime at the edge.
Refining and Straightening
Working cooler (dull orange-dull red heats) refine the shape in bevels using a lighter hammer with little crown. Use light blows with hammer to even out the edge. Work both edges down to even thickness, then refine the bevels and flatten the blade by sighting for thick spots or bends. Work only on the facets or the bevels never on the spine. Soap stone or chalk can be used on the edge to help sight the blade for flat/straight. Work cooler as final shape is reached, The last 2-3 heats of each section of the blade should be in the reds. This will help reduce grain size and leave the steel in it’s softest state for grinding.
The trade axe
This is a very common method for the making of tomahawks and small axes is the bow tie or wrap and weld method. There are several variations of this method. The first and most common is the cored body, this is when the core of the bit is lined with a high carbon bar, running from the edge to the eye this is a modern method, it take advantage of the relatively low cost of steel. The next method is the welding of the bit and then the addition of a high carbon bit, ( inset, over laid etc) other similar methods utilize a larger block and the eye is slit from the end and wrapped over then welded to form the eye. (placing the weld as the back of the eye. Other methods involve preshaping the piece to be wrapped before welding to form features such as langets, deeply bearded edges or thickened poles.
To begin cut or forge a 6-7” long piece of 3/8-1/2” thick 1-1 ¼” wide mild steel or wrought iron. Mark the center with a chisel or center punch, and set down a 4-5” long section to ¼” thick. (measure around drift to find length and forge to slightly under that amount.)
Use the edge of the anvil to set down a section approximately 2” from the center of the bar. Set down again 2” in the other direction from center and then draw an flatten the material in between the two to ¼”/1” . a flatter can be used to square up the shoulders and dress the set down section.
Trim the ends even approximately 2” from the shoulders . bevel the tips of the ends so that one side is flat and the other has both the shoulders and the bevels . bevel for a length of approximately ¾” and down to a thickness of 3/16” -1/4” thick. Alternately the ends can be left raw and the end trimmed later and a groove cut for the steel.
Now grind, file or scrape the flats and the bevels clean of scale. carefully heat the set down section and bend so that the two flats are lined up at the shoulders. Heat, flux and weld the joint. (see section on welding) When the weld is solid clean up the V formed by the bevels with a file. (or cut in V with chisel) Use a chisel to raise burs on the inside of the V. fit a piece of 1095 to the V by forging / grinding to shape. Cut and set the piece of 1095 in place Hot. (the burs should hold the steel in place) Flux and weld the joint .
Drifting the eye
Use a drift to open the eye hammer around the sides of the eye to expand it and then drive the drift in deeper, this will place less strain on the weld. Be sure to work all sides of the eye evenly so that the wall thickness will stay even. If the weld shears all is not lost re flux and re-weld the joint.
Forging to shape
Forge down the thickness of the bit, beginning at the edge. Greater width to the edge can be obtained by using a crass peen to direct the material movement. Work the sides over the horn to form the shape of profile. The goal is a cross section that is 3/8”-1/2” thick at the eye thinning to 3/16”-1/4” near the edge. Insert the drift and check to be sure that the edge and body of the axe is in line with the eye/ handle. If not correct this now. Forge in a edge bevel take the edge down to 1/16” and take the bevel back for a width of about ½”-3/4”
Flattening and straightening
Using a progressively cooler heats refine the shape of the axe using a lighter hammer (1-2LB ) with a firm blow. Pay extra attention that the edge and body of the axe are both flat, straight inline and centered to the eye .
mark the drift for the desired eye size. (this is determined by the handle size if a premade handle is to be used) work the edges and drive the drift down until the mark is even with the top of the eye or just a little shy. Be sure that the eye stays centered to the body and edge or the axe.
grind the profile to shape , be sure that all the grinder marks are running parallel to the edge. Once the profile is established, as much or a little finishing as you like can be done to the body and eye of the axe. The only other area or the blade that needs to be ground is the edge bevels. This area should be ground and polished , the thickness at the edge can vary with the intended use of the axe. A heavy working axe can have and edge a full 1/8” thick before sharpening. A lighter war axe can have an edge thickness before sharpening of as little as 1/16”. The remainder of the axe can be left as a forged finish or ground and polished .
Using a worn coarse grit belt, grind the edge on the flat platen or contact wheel of the grinder. Clean up the profile of the blade, re-shaping the tip as necessary, until the blade is even and centered. Next, run the blade edge vertically on the grinder so all grind marks run vertically on the edge. Next, use a small wheel attachment on the grinder to even out tang junction or grip area of knife. If a small wheel attachment is unavailable, use files to refine shape of the tang or grip. The joint area between the tang and blade should have at least a 1/8 radius (1/4 inch circle), ideally with no tool marks crossing the edge. This will prevent stress risers from forming and make for a stronger blade.
Once profiling is complete, begin grinding the bevels using a worn coarse grit belt on the flat platen. After the scale is stripped off use a fresh grit belt to grind the bevels flat with the edge up. When grinding everyone has a weak side and a strong side. Begin grinding with your weak side and match your stronger side to it, as this provides more control. Grind the bevels down until the spine is centered and even, the edge is of even thickness and about the thickness to of a dime. If the design has no hard plunge cuts, move to an 8- inch contact wheel with a 120 grit belt and grind the bevels vertically, until all coarse grit marks are removed. If the design calls for a hard plunge, re-grind on the flat platen. First grind using 120 grit, then grind with 220 grit. At this point the blade is ready for heat treating.
If tang is not square to center line of blade, file or grind until even or square.
If blade edge is of uneven thickness side to side or along one edge this can cause warping during hardening and will making sharpening difficult. Regrind thicker sections to match, adjusting the angle of bevel to keep spine centered.
Basic Heat treating
Basic heat treating for knife making is a three step process, it is the heat treating that is the most important part of making a knife. It is heat treating that turns a Knife shaped object into a knife. Step one normalizing, step two hardening, step three tempering.
normalizing, heat the blade to a orange heat and let cool to still air down to a black heat, do this three times . this will remove any stresses built up by grinding, reduce the grain size, and leave the steel in the best condition to be hardened.
Hardening is heating the blade to critical temp.(the temp. at with all carbon is in solution with the iron) and quenching it (in most cases in oil.) this will force the steel into it’s hardest state. Critical temp varies from alloy to alloy (usually between 1450-1550 DEG F) to find critical, heat the steel and check it with a magnet, the temp at which it looses magnetism is called the curie point, (1410 DEG F) about 100deg above this point is critical. In practice quenching from the point that the steel looses magnetism is close enough. judging the temp by color is affected by ambient light so even if when using a steel you are familiar with it is a good Idea to check the temp using a magnet. Heat the blade to this point and quench the blade in oil, quench the blade, edge down or tip first in oil, do not angle the blade when entering the quench or the blade will warp. For most steels vegetable or peanut oil works fine and is non toxic, motor oil can also be used,(fresh not used) as can transmission fluid. For a more consistent quench and when working with faster hardening steels a commercial quenchant like Parks-50 should be used. Quench the blade until all color is gone from the blade then let cool to room temperature. Check the edge using a file to be sure the blade hardened, if the file “skates “ then proceed to tempering. If the file “bites” the blade didn’t harden, reheat to a slightly higher temp and requench then check again. If the blade still isn’t hardening the edge may have decarburized, lightly grind the blade and check again if it is still not hard the steel you are using may not have enough carbon to harden.
Step three Tempering.
Tempering is heating the steel to 200-1000 deg F. This will take away the brittleness along with some of the hardness in the steel. The tempering temps will vary depending on the alloy used , size and type of knife being made. For the most part a temper of 300-450 Deg F for an hour is common. Hardness in steel is measured using the Rockwell C scale (RC) this scale ranges from RC30 (unhardened steel) to about RC70 for a med sized knife (6-8” blade) a hardness of around RC58-60 is about right a smaller knife can be harder (RC58-62) and a larger knife should be a bit softer.(RC52-58)
Temper ranges for common some common blade steels
(Temper ranges found online from various manufactures websites)
Understanding what is happening to the steel during heat treating allows the bladesmith to know when it is safe “to get away with something” and when it isn’t. It also allows the bladesmith to find solutions to the problems that crop up from time to time when working with new steel. Steel is defined as iron alloyed with carbon. All modern steels have alloys other than carbon, but all steels must have carbon present to be steel.
Definition of terms:
- Hardness is a measure of a resistance of a material to deformation. For steels, this is measured on the Rockwell C Scale.
- Harden ability is a measure of the steel’s ability to reach full hardness, both absolute hardness (at surface) and in depth of hardening (hardness at center).
- Toughness is a measure of the steel’s ability to withstand stress (resistance to shock, flexibility, deformation, etc)
- Each different alloying metal will change the properties of the steel. What each alloy and what different alloys together can do is a lifetime of study. As such, I will not go into further detail other than to say that most alloys are present to change the qualities of the steel (i.e. finer grain, higher harden ability, etc.).
Steel is a crystalline material and can form several distinct structures within the crystalline matrix. The first structure is ferrite, which is pure iron crystals in the steel with cementite (iron carbide) binding up the vast majority of the carbon. Ferrite is a body-centered cube of 9 atoms (8 iron atoms at the corners and one iron atom in the center) in which metallic alloys such as nickel can replace one or more of the iron atoms. When steel is heated above its “critical” temperature, a structure called austenite is formed. This is a face-centered cube of 14 iron atoms (again, metallic alloys can replace iron atoms in the structure), which can hold up to 2% carbon by weight between the iron atoms. For the most part, austenite is only present at temperatures above the austenizing temperature (beginning at 1375˚F). When quenched, austenite becomes martensite, which is hardened steel. Martensite is formed when austenite is “frozen” in the quench trapping carbon and is structured as a body centered tetragonal.
The goal of heat treating for bladesmiths is to free up the carbon from carbides and take it to solution with the iron (austenite) then quench to freeze the carbon into solution. In practice this is 3 main steps; normalizing, hardening, and tempering. The purpose of normalizing is to break up carbides, reduce grain size, and allow the ready formation of austenite. This will allow for a shorter soak time at temperature during hardening and finer grain martensite after quenching. Normalizing is defined as heating to the upper transformation point (about 1400-1500˚F) and slow cooling to the lower transformation point about (about 900˚F). Multiple cycles of normalizing can have greater benefits.( this is also called thermal cycling.)
The hardening step consists of heating to above the upper transformation point and cooling within a prescribed rate of time (quench). The length of time between heating and cooling is determined by the alloy (speed of quench). This rate can be found in a TTT (Time-temperature Transformation) chart. When mapped on a TTT chart the hardening curve will look like a nose. So long as the steel is cooled below the tip of the nose within the allowed time, it will harden. The TTT chart also shows the exact upper and lower transformation points, as well as the austenizing points, and the Curie point (the point at which steel becomes non-magnetic). After hardening the steel will mostly be martensite with residual carbides, and in the case of the higher-alloy steels there is often some retained austenite as well. Once quenched, the steel is in a highly stressed state. It is very hard, but also very brittle. By tempering (heating between 250-1100˚F) much of the stress is relieved , a portion of any retained austenite is converted to martensite and the overall hardness is lessened. As the hardness is lessened, the brittleness is lessened, and toughness is increased. A second cycle will temper both the original and newly formed martensite and convert more of the retained austenite to martensite. If the temper cycle is repeated 3 times 90% or more of the retained austenite will be converted to tempered martensite. For the average knife steel this isn’t really necessary since low-alloy steels have almost zero retained austenite after quenching. For blades made from high-alloy steels it can be worth the extra effort, and in some cases is actually necessary.
My method is to begin tempering 50 degrees below the finishing temper (i.e. a temper of 375˚F would be started at a temper of 325˚F). Soak at the lower temperature for 1 hour, remove and let cool. Then re-set the oven for 25 degrees higher, temper for 1 hour, remove and let cool. Then complete a final temper at 25 degrees higher, temper for 1 hour, remove the blade and let cool.
Steels come in three classes: hypo-eutectoid (less carbon than eutectoid), eutectoid, and hyper-eutectoid (more carbon than eutectoid). The eutectoid point (roughly 0.75% carbon by weight) in steel is the point at which the amount of carbon present has “saturated” the low temp material but is not yet sufficient for the formation of “free” carbides. In un-hardened steels all of the material should be pearlite, which is a mixture of ferrite (pure iron) and cementite (iron carbide). Below the eutectoid point the material will be a mixture of ferrite and cemintite and above the eutectoid point the material will be pearlite (ferrite and cemintite) with excess carbon binding as free carbides.
Hypo-eutectoid steels contain between 0.01% to 0.75% carbon by weight. Those steels above 0.4% carbon will harden and tend to be rather tough, though not especially hard. Addition of other alloys can improve hardness and hardenability. The hypo-eutectoid steels are generally easy to forge, grind, and heat treat.
Eutectoid steel is the range right around 0.75% -0.85%carbon by weight. These steels will harden very well and tend to be forgiving when working with them, but do not have the added toughness of hypo-eutectoid steels without added alloys. These are the best steels for beginning bladesmiths due to their forgiving nature and relatively high performance.
Hyper-eutectoid steel is between 0.75% to 1.25% carbon by weight. These steels can yield the highest performance because the excess carbon can form various carbides. They are almost always found with high alloy content, especially such carbide-formers as chromium, vanadium, and tungsten. When treated properly these steels have the best edge-holding and wear-resistance properties, but they are temperamental to work with and react poorly to overheating. Good knowledge of metallurgy and proper control of forging and heat treating temperatures are a must before delving into this group.
After heat treating lightly regrind the blade using a 120grit belt (remember to keep the blade cool) then move to the 220 grit belt and then the 400 grit. (or begin hand sanding at any point) Begin hand sanding starting with one grit lower than the last grit used on the grinder. Sand at an angle to the last grit until and even surface is achieved with no lines left from the last grit, then move on to the next grit. Again at an angle to the last grit sand until all mark of the last grit are removed. The last grit used should run length wise on the blade for the best finish.
For a brighter finish, the blade can be polished using a buffing wheel. Charge the wheel with emery and buff the blade. Clean the emery off with acetone and buff with green chrome.
A word of warning here the buffer is a very dangerous tool , do not present an edge to the wheel or it will catch on the wheel and be thrown. Knife makers have been seriously injured when a blade they were buffing caught and was thrown at them.
use a Hack saw to slot the handle block slightly over length for the tang. Clamp the grip in a vice and carefully heat the tang of the knife to around 900 DEG F. Then use the tang to burn out the slot for a perfect fit. If the blade has been heat treated be sure not to heat the tang past the junction to the guard as this will result in having to re-heat treat the blade. If this is a concern, a bar of steel may be shaped to match the tang used to burn out the handle material. Once the tang is fit, let the tang cool and assemble and drill the assembly for pins. Rivets. Disassemble and use the pin holes to line up the blade then trace the Tang on to the handle material. draw in the profile you want for the handle on the marked side of the handle. Using a hack saw, band saw or belt grinder, rough in the shape to these marks. Repeat for the other 2 facets. Then, round and shape the grip as desired. Adjust as necessary for fine shaping a rasp followed my course files work extremely well. Hand sand the handle/grip to about 400 grit for the best finish.
When hand sanding wood always sand with the grain. Lightly wetting the wood to raise the knap will result in a finer finish
dye or stain between grits starting at around 200grit for the best results.
After re-polishing, assemble the knife and re-check all fit ups. Disassemble the knife and lay out all parts in order and in the proper orientation. Mask off the blade with tape (be sure to keep the blade in the proper orientation ) Mix up epoxy and coat the tang. . Next, coat the inside of the grip and anywhere the grip will contact the guard; along with the spacers if any are used, insert the tang onto the grip. Clean off excess epoxy and let set up by clamping in a vice point up. Wax can be used to clean off epoxy. Once the epoxy begins to set, scrap off any remaining epoxy. Re-polish the grip. Remove the tape from the blade and clean with WD-40, acetone, or denatured alcohol. The blade, guard, and grip can now be waxed or oiled.
- A brass chisel can be used to clean off excess epoxy that has hardened on the blade without scratching.
- Applying WD-40 to a rag will ease in removing excess epoxy.
- A coat of wax on areas that epoxy shouldn’t be will add in cleaning it off
- Mix a good amount of epoxy. (Mix more than is necessary; better too much than too little.)
- Fill the cavity in the antler almost to the top.
- Spread epoxy on the tang and on any surfaces that contact each other.
- Clamp in a vice point up. do not move the knife until the epoxy is set up.
- Once the epoxy is set, but before it is fully hardened, any remaining epoxy can be more easily removed with a wooden or brass scraper.
The first edge on a newly finished knife should be cut in with the grinder to establish a secondary bevel. Once this is done, the edge can be re-sharpened or further dressed with stones.
On all knives with a secondary bevel (basically anything other than Japanese style work and razors), there are three types of edge: flat ground, convex, and concave (hollow ground edge), Most production knives have a flat ground edge of 15o to 25o. A flat ground edge can be easily re-sharpened and cuts well, Most custom knife makers use a convex edge of the same basic angle of 15-25. This type of edge is just as sharp as a flat edge, but it is stronger, and able to hold an edge longer. It is how ever slightly more difficult to re-sharpen with hand stones. The concave edge is a style that works well for some knives, such as meat cutting knives, that a steel will be used to sharpen but is of limited utility for an everyday knife as it is a relatively weak edge, will dull quickly and is impossible to re-sharpen with hand stones.
As said most custom knife makers use a convex edge, to set this type of edge the blade is ground on the slack belt of the grinder. ( I generally cut the edge with a 120 grit belt making sure to cool the edge frequently. ) Hold the knife edge down at a 10o angle, (as measured from the center line of the blade to the grinder) starting at the base of the blade press in slightly, and take one continuous pass along the whole edge. Cool the blade down and repeat these steps on the opposite side. Continue this process alternating sides until a burr (wire edge) develops all along the edge.
At this point move to a finer belt (220 grit) and continue alternating sides. Then, use 400 grit belt to re-polish the edge. Afterward strop the edge on the buffer to remove the bur. The knife should be sharp. If the edge is not sharp after buffing, re-cut the edge at a slightly steeper angle and go through the steps again.
NJ steel baron carry’s all types of bladesmithing steels
Gesswein source for high speed steel gravers , as well as EDM polishing stones
Supergrit grinding belts and good sandpaper (rhinowet)
- Wayne Goddard
- $50 Knife Shop
- Wonder of Knife Making
- Jim Hrisoulas
- The Master Bladesmith
- The Complete Bladesmith
Machinery Handbook – (Pub.) Industrial Press
On the web
- Bladesmithsform.com best overall bladesmithing forum
- Jerzeedevil.com very active and intresting forum.
- Hypefreeblades.com best heat treat and metallurgy forum
- Myarmory best historical blade forum.
- Cashenblades.com great metallurgy and heat treating references