By Matthew ParkinsonDownload Tutorial
Dealing with Medium and High carbon steels.
When making a knife a high or medium carbon steel is needed. This kind of alloy is also called sometimes called “spring steel” (a alloy that springs are made of) or “tool steel” (one of a selection of alloys intended to make tools out of) theses terms should be understood to just be very rough classes of steel rather than a specific alloy. When working with these steels the higher the carbon content and the higher the alloying content the more sensitive the steel will be to correct temperature ranges. Some of these alloys can be red hard (a temperature range that the steel to hard to work) or red short (a temperature range that the steel is prone to cracking of 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 severely over heated or held at high temperatures for long periods. Large grain size weakens the steel and is detrimental to the cutting ability of the finished knife.
The best way to avoid damaging the steel you are working with is to know what alloy it is that 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 forging heat range is, what the hardening and temper ranges are. (you will need this info later) With any of these alloys there are a few things that should allways be done. First Do not soak the steel in the forge for no reason, 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 temperatures. And finally normalize the steel before finishing the knife (filing grinding etc) to normalize heat the steel to past critical temp, the critical temp can be found by using a magnet to find the curire point,(the point that heated steel turns nonmagnetic) critical temp is for the most steels fifty to hundred deg. Higher than the curie point. Heat around 1600 degF (200 deg past Currie point) and let cool in still air to the recolessance point (around 900DegF), 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 and sold 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, theses 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.
What is a Seax? The Seax (also spelled as Sax or Sæx) is the knife of the Vikings, but also the knife of all of early Europe. It was carried by the Goths, the Vandals, the Brits, the Anglos and especially the Saxons. The Saxons identified with the weapon so closely that their tribal name was derived from the word Seax. (seax litterly means knife, so the saxons are the people of the knife) The Seax ruled the sheaths of Europe from the 4th century until the 11th century and were carried by all walks of life. The Seax can vary greatly in form , from a small 5” long scramaseax used for every day tasks, to the 24”+
Langseax used in defense. Many but not all seaxs are pattern welded and the complexity of the patterning vary s greatly with region, time and presumably with the wealth of the original owner. There are several shapes of blade that can be considered a Seax. Generally speaking they are single edge blades with a straight cutting edge forming a single bevel from edge to spine. No seax I have ever encountered has a ricciso the the primary bevel always runs from edge to spine and continues into the handle. The point can be centered or set to the top or bottom of the blade.
Seax typology retrieved from SFI.COM and myarmory.com post by Kirk Lee Spencer
The one style that stands out with in this frame work is the Broken-back, this type of Seax show up all most entirely in the UK and further differ from the few that are found on the continent. Those found in the UK tend to swell from the base to the break in the spine and have a straight edge with a bit of belly coming to the point. The continental broken backs tend to be narrower and to have a parallel cutting edge and spine. The points on this style are centered toward the cutting edge, a small amount of up sweep is
common. I have seen a small group of seaxs showing up on Ebay that a reputed to be Frankish/ Merovingian dating from 450-750 that seem to be broken backs with a a bit of re curve with fairly parallel spines. With out examining them or reciveing better Provenance on them I don’t want to call these common but they are legitinit enough I feel them worth mention. For the classic Saxon broken back found all of the Britain, The break or clip is normally flat but a large radius or sweep is also seen as it the so called Kentish Notch. This style has little to no distal taper, in fact in some cases
they can have a reverse distil taper, that is to say they thicken at the spine up to the widest part of the blade. The length of the tip also varies greatly from a short abrupt clip to a long and stretched out needle like point. These can vary in size from small 3-4” blades all the way up to langseaxs of 28+ inchs.
There are several typologies in use describing the seax all based on common groups of like blades or groups of blades that based on finds come from the same time and general area. There are how ever many small groupings that do not show up in the larger overall record that can be interesting , for instance a group of broad seaxs found in an area of poland belonging to one of the Balt tribes has a fascinating T backed cross section not seen on any other seaxs. Regional changes and tribal differences in form, not just in ornamentation Form a strong indication that unlike the double edged sword blades of the period the seax blades were locally manufactured. For the most part a clear linage is recognizable even with these outlying forms. There are a few forms that are ether divergent or unrelated forms. A good example of this is the large broad seaxs of the vimose type that have a very unique tang and grip construction , they are all most a full tang with an upset inner edge forming a T cross section the grips are very short, and unlike other seaxs offset to the back of the blade. They have a very unique handle shape that is not seen in other seaxs but is reminiscent of the falcuta so they may be related to that (though coming from finds in Denmark that seems unlikely) or they may just be an interesting tribal off shoot of the seax.
Historical Pattern welding
Pattern welding began as a way to improve the available steel. It quickly evolved into both a decorative technique and a way to improve the strength of the steel.
The Viking era smiths choice of alloy would have been based on, first carbon content, and second on the trace alloying elements (vanadium, phosphor, manganese, chrome, nickel etc) the carbon content would most likely have been tested by hardening a short section of a bar and breaking it to check the hardness/ brittleness. Bars of steel would then be graded based on hardness and mixed in the laminate for the desired hardness or carbon content in that area of the finished sword. (Harder at the edges and softer at the core) the Ideal would be for the edges of the blade to be very hard the area just behind the edge to be springy and tough and the very core of the blade to be almost dead soft. This combination allows a safety factor to be built in to the blade. The hard edge will hod a sharp cutting edge, springy area will support the edge and allow the blade to flex and return to true and the soft area at the core helps to absorb shock and resist fracture. This helps to ensure that if the blade is stressed past its yield point that it will bend rather than snap. The edge is the only area of the blade that needs to be hard, this hardness allows the blade take and keep a fine sharp edge but must be balanced with softer areas of the blade or it will crack and snap in use, with the soft core, if the blade is over stressed to its’ failure point any cracks that do form can not precipitate across the whole of the blade allowing the blade to still be fought with.
This perfect balance of hardness spring and soft is all but impossible to reach with such inconsistent materials, so wail Viking smiths did the best that they could they tended to error on the soft side ensuring that if the blade was forced beyond it’s yield point it would bend rather than snap. A bent sword can still be fought with a broken or snapped blade could cost you your life in a fight.
The next factor in choosing an alloy is the trace elements these elements can affect the heat treating somewhat, (less so based on the hardness test rather than on a know carbon content) but the real affect of these added elements is in the finished blade. Deference’s in chrome, nickel will tend to etch silver and additions on manganese, vanadium or phosphor will tend to etch blacker. The addition of Phosphor might have been important not just for the look but also for the performance of the blade Phosphor can block carbon migration in steel, helping to segregate the various areas of the blade and keep the intended carbon level isolated.
I do not know how or even if the Viking smiths graded the steels for these elements, if they did I don’t know how they went about it. I have read nothing that addresses this point. That being said, I do feel that they must have graded the bars somehow and in examine photos of surviving blades and in the limited x ray studies I have seen there appears to be differing alloys used purposefully in the pattern. My understanding is that the blades were etched to show the pattern, but even if not etched when differing alloys are used a subtle pattern is still visible when the blade is polished. If the pattern is only based on differences in carbon content the pattern would not show in this way and would be far more subtle even when etched with acid.
My best guess on how the Viking smiths would grade the steels for color is that a small window was polished in to the bar and etched with a mild acid (vinegar, tanic acid or some such) then graded against each other. It is also possible that the grading was done based on where the bars were acquired. i.e. knowing that a bar made from this ore from this furnace would etch blacker than one from this other ore. This seems unlikely as a finished bar from any ore looks much the same and I find it unlikely that these could be keep separated for any length of time or with any degree of certainty.
Using modern steels
First choosing two complementary alloys will go a long way to making the pattern weld work. several combinations are common (L6/O1 15N20/1080 8670m/1095 etc) these common mixes all work well together and show good pattern. What will show pattern in the finished blade are deference’s in nickel, chromium and manganese the first two will show as brighter line in the pattern darker lines are due to a high Manganese content to one of the alloys. The next thing to think about is the total carbon content of the finished billet, carbon will pass across the weld boundary after around three welds the carbon will be evened out. So the total carbon content needs to be high enough after welding to still harden. Choose two alloys with similar working propetys, forging range, austenizing temp, hardening rate and temper ranges should all be close with the two alloys this will allow for easier heat treating later and will help ensure that he alloys will work well together rather than fighting with each other when forging or heat treating.
A good example of complimentary alloys are 15n20 and 1070-1095 15n20 is basically 1075 with about 2% nickel with these mixes the end carbon content is around70- 80 points and the finished billet should heat treat about like 1084.
On the other hand a very bad choice for a cutting edge would be mild (1018) and 4130 this might show good pattern but the billet would not have enough carbon to harden.
The next choice is the over all pattern. All Viking patterns are based on twists change the topography. What pattern you choose will determine how many bars you need in the laminate And how many layers in each bar.
I have heard and read that all Viking pattern welding began will billets of 7, 9 or 11 layers, this may or may not be true, but I have found that sticking to these layer counts looks “right” in this type of pattern welding so I tend to use them. For some of the continental styles (Merovingian and Carolinian etc.) I have noticed slightly higher layer counts of 15-20 layers of so. The key elements of this style of pattern welding are relatively low layer counts, multi-bar construction and very little material removal to affect pattern development. With almost all of the patterns twisting is used to develop the pattern. How tightly twisted and how the twist interact with each other forms the pattern. In some of the more complex methods of construction the twisted bar is cut in half and inverted so that the core of the twist show to the out side, this depending on how much is removed by grinding makes a checkerboard, star or X pattern.
Methods of modern pattern welding
The part of pattern welding that is always the greatest fear for any new bladesmith is the 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 steels used are what cause the pattern to be visible when etched.
To form a successful weld 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 oxides on the surface to breakdown or 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 using more than one method. 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. In this method 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 restack. 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) 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 however 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, reading every thing you can on the subject is advised; understanding how something is working can go a long way to helping diagnose problems when it suddenly stops working.
For this purposes of this class the seax made will use a 3-5 bar laminate, this will allow for many varying patterns. We will weld two billets laid out as follows.
For illustrating the starting billet arrangements FE=3/16 1084 fe=1/8” 1084 Ni=095 15N20
Next a 9 layer billet – FE/NI/fe/NI/FE/NI/fe/NI/FE
And an 11 lay billet- FE/NI/fe/NI/fe/NI/fe/NI/fe/NI/FE
When welded these billets should have an average carbon content of about 80 points and should heat treat about like 1080. you can compute the total carbon content to a fairly close degree by adding up the total amount of thickness of the billet, next add up the amount of thickness of each alloy. Use the thickness numbers to figure out the percentages of each alloy. Use the percentages to find the meen average of the two steels carbon contents. This is not necessary when using 15N20 and 1084,1075 or 1095 as theses mixes in any ratio will end up with a good carbon content.
The flux weld in practice
To begin prepare the billet to be welded by stacking tightly clamping and welding the corners to hold it together or bind the stack tightly together with iron wire. At this point a handle can be welded on or tongs can be used to hold the billet when welding.
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 degF) 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 used in viking style pattern welding. note on the hammer used for welding, the size of the billet you are making will to a great extent determine the size of the hammer needed, and the larger the billet the larger the hammer needed. A heavier hammer will transmit more force to the center of the billet than a lighter hammer. For this reason there is an upper size limit on billets that are practical to weld with out a power hammer or forging press. If only the core layers are taking try a lighter hammer as too much of the force could be going to the center of the bar.
Common issues with welds
Trapped flux – to prevent wire brush and reflux often and do not over flux the joint, there should be just enough flux on the joint to wet it when heated. Do not soak at temp to long and over lap the welds working form the welded section back. To repair scrape out the trapped flux and re-weld. If possible cut out this section or work around it.
Weld sheer- To prevent this work only at a higher temp, and KEEP THE BAR Square to the welds
Repair when possible by resquareing the bar then fluxing and re-welding.
Sections not welding-to prevent be sure the bars are clean and fluxed and at a high enough temp to weld. To repair wire brush and reflux 2-3times to remove any oxides that might have formed before attempting re-welding.
Oil weld or Bare back weld
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. Electric welding the billet together works best as the weld areas need to be held in close proximity when heating, though Wiring the Billet together is a possible option. Place the billet in the forge and bring it up to a welding heat, soak it at temp for 4-5 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.
Preparation for patterning
Once welded (what ever method used) the billet can be draw out with a hand hammer, with the help of striker, or with the help of a power hammer/ forging press. How the bar is drawn out is irrelevant, it is how ever of the utmost importance the all forging is done parallel or perpendicular to the welds, if the bar is forged at an angle it will place undue stress on the welds and can lead to the weld sheering this becomes less and less important as the bar is drawn out and the welds become stronger. Off angle foging can also affect the look of some patterns and make them difficult to predict. It is a good Practice to adjust any angled forging as soon as it is noticed before the weld has a chance to sheer. Work the billet only above a orange heat to place as little stress as possible on the welds. This is especially important when forging the blade from the patterned billet as forging in the edges must be done on angle to the weld and places a great deal of stress on the welds.
Common types of Patterns and how they are formed
Chevron-This pattern is formed two bars of opposing twists a more interesting version of this pattern can be had by stopping the twists and reversing them farther up the bar. Single twist- a single laminated bar tightly twisted this pattern must be forged close to final shape grinding to deep will alter the pattern.
Straight- the patterned bar is welded in so that the edge of the laminet is showing.
Reversing twist – a tight right hand twist that runs into a tight left hand twist .
X or stars pattern is formed when 20-25 percent of the twisted bar is removed after forging.
Checkerboard this pattern is formed by cutting a twist in half and inverting the bar so that the inner core of the twisted bar is shown. This pattern must be fogred close to shape of the pattern will be altered.
Serpent This pattern is formed by reverse twisting a bar with 90* twists. I find the best pattern is obtained by twisting this pattern thicker than normal 5/8’-3/4” and then forging one face down to 3/8”-1/2” thick and just flattening the other facets forming an off size bar around 5/8” /3/8”
When planning the pattern remember that more than one pattern can be used in a blade. For example a serpent pattern can be flanked by a chevron above and a flat laminate into a reversing twist below. Or a single bar can change pattern with in a blade Ie- at the base a tight twist into a straight into a reversing twist.
Lastly it is best with all twist patterns to always twist tighter than you think it needs to be as the pattern will stretch in the forging. In the case of the reversing twist of a serpent to twist the shortest section possible. It can also be helpful on chevron and similar patterns to do the twisting closer to final thickness, this can make it harder to weld the laminate together but will allow more control of the pattern stretch.
Begin by planing out the pattern for the seax. A finer pattern welded bar (of 25 +layers) or a piece mono steel can be used for the cutting edge (this finer bar can be had by restacking a portion of the 9 or 11 layer billet to the required layer count.) What ever the choice the bar should be reforged to match to the size of the remaining parts of the billet. 0nly what will be the cutting edge should be made of this finer patterned steel. Then plan out the remaining 3-4 bars of the pattern. All the bars can now twisted to produce the desired pattern and cut to length . The twisted bars are ground clean and flat on two opposing facets and laid out for assembly.
Then ends of these bars can be tacked together with a TIG or MIG welder to hold them in place with a handle welded on or the assembly can be wired together and tongs used to hold the billet for welding. If using tongs I like to leave one of the bars 2-3 inchs to grab with the tongs. The billet is then welded together just as the main billets were. Beginning at one end and working troward the other end. Over lap every welding heat by at least ½ and work from welded section on to be sure the weld has taken. Once the billet is welded solidly forge in the thickness to around 1/4” thick (or the thickness of the spine) at this point trim off the electric welds on the point side . For the best look to the pattern at the point I clip off the point at an angle this will allow the pattern to follow the edge more evenly at the point.
Forging the shape
once the pattern welding is complete and the billet is forged to thickness with the tack welds removed and the tip of the bar trimmed, begin forging in the over all shape. Forge tin the point and a small amout of distel taper. If making a broken back seax, forge in a small amout of taper from the break in the spine back to the tang side of the blade. The amount of taper can vary but I like around 3/8” or so of taper on a blade of 6-8”
With the profile of the seax mostly forged in The tang should forged out. A step in and long taper of 6-8” is best if it is to pass through a handle and be riveted in place other wise a short tapering tang of 2 -3 inches is common.
Forging in the tang
Once profile is forged to shape, set in the tang using a spring fuller. Be sure to account for the amount of growth in length due to beveling, if a certain length is desired bevel the blade first then sent in the tang once the blade is to length. The tang should remain ½ to 2/3 the width of the blade at this point, cut off leaving 1-2 inches of stock after the step forged in from the spring fuller. Then, forge out the tang to a taper 1/3 to ½ the length of the handle, for a stub style tang. If making a through tang seax. Be sure to leave more material on the knife when cutting off and forge the tang out to 1-2” longer than the finished knife handle. The extra length can always be easily trimmed off but adding length is much more difficult. Remember that most seaxs had very long grips by modern standards, 6-8” being common.
- Use the end of each heat to flatten the blade before re-heating.
- Only work the steel down to a bright red heat. DO NOT soak the steel at a high temperature in the forge.
For most of the point shapes the blade is forged out as with any modern shaped knives excepting the lack of ricisso. The broken back Seax how ever can cause some problems.
For the broken-back I begin by forging in the basic profile. I find the pattern looks best if the end of the patterned bar is cut at 45-60 Deg. angle and then the profile is forged in. If the point is fully forged in to the profile the pattern will get stretched and look “off” crushing down along the edge. In the finds I have examined and in those I have studied photos of both methods seem to have been used in period. This same technique can be used for other patterns of seax depending on the intended pattern at the point. If an angle is cut across the pattern and then the point forged in the pattern will tend to follow the edge and run up off the spine. If no cut is made and the point is entirely forged in the pattern will shrink down as the point narrows and it runs off the tip. All ways try and keep in mind what the pattern will do as it is forged out and try to work the material in a way that directs those changes in the direction you want rather than the reverse.
No distal taper should be forged in to the blade until the point that the broken back begins, forging in a good amount of distal taper to this area will help later in preventing the tip from shifting as much when forging in the bevels but to much distal taper can shrink the pattern as it nears the point.
Forge in the bevels beginning at the point. As the point rises force it back down keeping the cutting edge to the desired shape. Set the edge down first working form both sides with even angles to keep the pattern centered and to put as little stress as possible on the welds. Continue the bevels up the side of the blade all the way to the spine forging in the last of the distal taper with the bevel. 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 concentrate on keeping the edge centered the angle of the bevels even and that the edge is of an even thickness. Forge the bevels to a thickness about that of a dime at the edge. Forge the bevels all the way into the tang
All of the forging should be done HOT do not forge bellow an orange heat. The more material movement, the hotter the material should be. After the blade is close to finished shape, cooler heats can be used to refine, straighten, and flatten the blade. I Leave the blade a little thicker than I do with a mono steel blade. This is to allow for minor surface flaws due to flux inclusions or the edge of a bad weld to be ground out. Begin refining the surface and shape, Working cooler (bright orange to red heats) refine the flats of the bevels using a lighter hammer with little crown. Use light blows with the hammer to even out the edge. Work both sides of the edge down to even thickness, refine the bevels and flatten the blade by sighting for thick spots or bends. Soap stone or chalk can be used on the edge to help sight the blade for flat/straight. The more even the forging the more even the pattern will remain, if to much needs to be ground out to adjust for some error in forging, the pattern will reflect it. When refining and straightening work cooler as final shape is approached. The last 2-3 heats should be in the reds. This will help in the accuracy of the forging and will begin to reduce grain size and leave the steel in it’s softest state for grinding. Once the blade is as straight and flat as possible, take a normalizing heat. To normalize, heat the whole blade to non-magnetic and cool in still air; normalize the blade 3-4 times before grinding.
Soaking the blade in Vinegar over night or in Ferric chloride for a few min will remove the scale and make the grinding far easier. The scale will dull the belt quickly and make the blade difficult to grind. If etching isn’t an option use old belt to clean the scale off then switch to a fresh belt to do the more controlled grinding.
Begin by profiling the blade using a worn 30-60 grit belt. Grind back the profile shape and even out and adjust the lines of the knife. Leave the tight radius on the inside of the tang to be filed in later. After grinding the profile to shape run the spine and edge lengthwise on the grinder. This is to make the tool marks run the long way rather than crossing the edge. Any tool marks running across the width of the edge or spine will be a stress riser and run the risk concentrating stresses leading to cracking in hardening. This isn’t all ways the case but running the tool marks the length of the blade is cheap insurance against a cracked blade.
Now begin grinding the bevels using a fresh 40-60 grit belt. With the edge up grind the bevels, set the angle with the first pass and stick to it, you can adjust the angle by adding pressure to one side or the other, as you grind but try not to set a new “facet”. Grind along the flat from the base of the blade into the tang. Cool the blade in water as soon as it is to hot to touch but try and keep you hands dry; wet hands will get burned much sooner than dry hands also be sure to dry the blade before grinding again as the water tends to glaze the belts. Grind one bevel down to clean metal then begin grinding the reverse side. Keep the same angle from side to side and from pass to pass. Grind the flats down until the edge is centered ,straight and about the thickness of a dime.
Switch to a 120 grit belt, re grind the flats with the finer grit belt so that the grinding marks run the length of the blade. Careful use of the 8” contact wheel can aid in evening the flats. If the results from the grinder are less than acceptable a file can be used to flatten and even out the bevels.
Even out the tang transition and any other hard to reach areas with a small wheel attachment on the grinder or by using files. Be sure that all tool marks run the length of the blade to prevent stress risers, this is cheep insurance. Remember that a file only cuts on the forward stroke, so apply a small amount of pressure when pushing the file away from you, and release the pressure when you draw the file back. Just a small amount of pressure is all that is necessary, just enough to get the file to “bite” any more is a waste of energy and will just make the file cut slower and wear out faster. Take the blade to at least 120 grit or the equivalent before heat treating.
The main goals of grinding are to make the bevels as flat and even as possible. The cutting edge should be around the thickness of a dime and as even along the length as you can make it. The spine to should be an even thickness of an even taper with no drastic changes in thickness.
Basic Metallurgy and heat treating
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.
- Hardenability is a measure of the steel’s ability to reach hardness, both absolute hardness (at surface) and in depth ofhardening (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 hardenability, etc.).
Steel is a crystalline material and can form several distinct structures within the crystalline matrix or lattace. 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 in the interstitial spaces of the structere of iron atoms. For the most part, austenite is only present at temperatures above the austenizing temperature (beginning at 1335˚F). When quenched, austenite becomes martensite, which is hardened steel. Martensite is formed when austenite is“frozen” in the quench traping the Carbon in the interstitial spaces and shifting the structure to a body centered tetragonal.
The goal of heat treating for bladesmiths is to free up the carbon from carbides and take it into 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 grained martensite after quenching. Normalizing is defined as heating to the upper transformation point (about 1600˚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 unique to each alloy. 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 temperature use to generate that curve. 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,converting the structure to Tempered Martinsite by releasing a small amount of the trapped carbon, in addition 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 temper 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 blade 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 pearlite and above the eutectoid point the material will be a mixture of pearlite and 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% carbon by weight. These steels will harden 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 ease of heat treatment and relatively high performance.
Hyper-eutectoid steel is between 0.85% 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 of alloys
Basic heat treating
Basic heat treating for knife or Axe 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.
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. As long as normalizing was done prior to grinding a simple stress releaf can be used rather than a full normalization. To stress relaeve heat to 1200-1300 DegF and let cool. This method reduces the risk of Decarb and the amount and depth of scale that will need to be removed after heat treating.
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, (1500DegF for 15n20/1084 mix) the simplest method is to heat the steel and check it with a magnet, the temp at which it looses magnetism is called the curie point, the curie point is about 50-100deg below critical. In practice quenching from the point that the steel looses magnetism is generally close enough. judging the temp by color is affected by ambient light so even 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 most likely 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 but is not recommended due to the toxicicty of the fumes. For a for the best, most consistent quench and when working with faster hardening steels a commercial quenchant like Parks-50 should be used. The speed of the quenchant should be matched to the speed the steel you are working with requires. 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 150-1000 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. (a temper of 425 DegF for a seax of 5-7” is about right) 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)For a bit greater performance three cycles of temper can be done, the first 50 deg below the finished temper. For example for a temper of 350 start with one hour at 300, let cool then one hour at 325 let cool and a final temper of 350 for an hour.
Temper ranges for common blade steels
Steel AS Hard 300 Deg 400Deg 500deg
1050 RC59 RC55 RC52 RC48
1075 RC64 RC62 RC59 RC58
1084 RC66 RC64 RC60 RC55
5160 RC62 RC59 RC56 RC54
O1 RC64 RC62 RC60 RC58
W1 Rc65 RC63 Rc61 RC59
(Temper ranges found online from various manufactures website)
Polishing and etching
Regrind the blade to at least 220 grit, then begin hand sanding at 100-150 grit. Use a sanding block and sand crossways to previous grit to ensure all previous grit marks are removed. To speed up hand sanding a palm sander with a hard backing can be used for the first two or three grits, the final grit before etching should be done by hand using a back up pad. ANY deep coarse scratches left in the finish will show up in the etch so be sure to have as even a surface as possible. a finish of at least 220 grit needs to be present before attempting to etch 400 grit is preferred. Many Acids will work to show the pattern, the most common one used in the knife making world is Ferric chloride. A relatively safe acid to work with it is often sold as circuit board enchant. An approximately 10% solution of ferric chloride and distilled water seems to work best but I encorage you to expaiament and fide the mix that works best for you. Prepare the acid in a acid safe plastic or glass container that is deep enough to hold the whole of the knife that will show above the grip in the acid. (always add acid to water never the reverse )
Now prepare the polished blade by washing it with dish soap and water to remove any oils on the blade, dry the blade and be sure not to touch it, any finger prints on the blade will ruin the etch.
Submerge the blade in the acid and suspend it for 1 min or so. remove the blade and check to be sure that the whole blade is etching evenly. If it is, replace it in the acid. If not, rinse and wet sand the blade and then replace it in the etch. Check it again after 1 min or so, if the blade is still not etching evenly, try wet sanding and washing with soap and water. Once the blade is etching evenly, etch for about 5 min then remove the blade rinse and lightly wet sand the blade with 400grit. Replace the blade in the etch for another cycle of 5 min. repeat using 600 grit paper until the desired depth of etch is achieved. The amout of time and number of etchs it take to get a nice deep clean etch on the blade will depend on many factors from the temp of the acid to the underlying structure of he steel. The remaining acid on the blade needs to be neutralized. For ferric chloride baking soda or ammonia (windex works well) can be used. The blade should be Then rinsed thoroughly dried and immediately oiled or waxed to prevent rusting. For a darker contrast, after a deep etch has been achieved the blade can be blued (hot of cold gun blue) that the highs re-polished using worn 600grit paper on a hard backing. I have found the OxPho cold blue from Brownells to work well and give a nice dark blue/gray black.
Making and fitting the grip
Very few Seaxs have been found with intact handles. They and the few found with metallic guard or pommel fittings along with contemporary art give us clues as to the shape length and thickness of the grips. The grips do seem vary greatly with the differing types of seaxs. But other than the Norwegian sword hilted longseaxs none that I have seen have guards that are much wider than the blade.
Generally Seaxs tend to have grips much longer than is normal on modern knives, 5-8” being common. Oval or a D shaped cross sections being most commonly seen. For the most part seaxs were hilted entirerly in organic materials (wood bone horn or antler) leading to the few hilts remaining. Some few have been found that have grips that are heavily carved, geometric Knot-work and zooamorphic themes seem common. The style of ornamentation being determined by the tribe, time period, and area.
What ever the design with the blade ground and poilshed draw the tang on the handle material then lay out the shape of the grip on the wood. Mark a center line on the side 90 Deg. from this layout. Use a square to continue these lines to the top of the material. Using these lines as guides, clamp the material in a drill press and using a slightly undersized bit drill out the slot for the tang resetting the handle block in the vice to drill both angles of the tang. Scrape out most of the excess material then clamp the material for the handle in a vice and carefully heat the tang of the knife to 500- 900 DEG F. Then use the tang to burn out the slot. As the blade has been heat treated, be sure not to heat the tang passed the junction to the blade as this will result in having to re-heat treat the blade. If this is of great concern, a bar of steel may be shaped to match the tang and this used to burn out the handle materiel. Check the fit between the blade and handle and adjust if needed
Optionally a bolster can be made from antler horn or another type of wood and this piece filed out to a better fit with the blade. Once the tang is fit,if using a bolster fit that then remove material from the top of the grip to get the back of the bolster and the handle to meet up flush with the tang bottoming in the handle.
Check to be sure the drawn in handle profile is still centered. Use the draw in the profile as a guide to remove material and shape the grip. Using a band saw or belt grinder is faster but easy to go to far and ruin the shape. Using a hand saw, a rasp or file is slower but easier to control. Rough in the shape to the marks (at this point if a pin is included in the design drill and fit that fit that then continue: though I have never see a pin included on any but the vemos type seax). Draw in a center line based on the blade. Then draw in the other profile and repeat the material removal for the other 2 facets. Double check that he blade is centered to the roughed in grip check the handle and blade are lined up and adjust as necessary. Round and shape the grip for rounds of ovals take the corners off and make an octagon. Then round by removing the corners of the octagon and finally by blending out the high spot and rounding with a file or sand paper.
If the design is a through tang a washer should be made to fit the tang were it sticks out of the back of the handle, this can be nothing more than a stamped washer from the hardware store filed to fit, to an elaborate rosette. The fit should be tight so that the washer needs to be forced down the last 1/8” or so of the tang. I find it looks best if the washer is inset slightly into the handle material. A small chisel can be used to remove the material. With a through tang a thin bolster plate, ferrule or a bolster made of antler or horn is a good idea, helping to prevent the tang from splitting the wood when peened. Another option is to use a slightly looser fit washer and bend the tang over rather than peen it , this method is also see on many originals. I suggest if doing a peened tang or the folded over design to weld or braze on a piece of soft iron or steel to the end of the tang this makes the peening far less likely to crack and chip out when peened. The end of the tang can be used but be as sure as possible that it is fully annealed.
Hand sand the handle/grip to at least 400 grit for the best finish. When finishing wooden handles I generally sand to 120 and then apply any stain I am using. I let that dry and sand at 220 reapply any stain and then move on to 400 grit. If no stain is being used I wet the wood with clean water between the final few grits to raise the nap for a finer finish. At 400 grit I begin applying oil. ( Truoil is a old stand by that is highly recommended) I generally do 2-3 coats of oil using super fine steel wool between coats. I use steel wool to smooth the surface of the final coat of oil and finish off the grip with a bit of wax buffed with a soft cloth. (furniture wax, paste wax,gunstock wax all work well giveing slightly different finishes)
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. After wards 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.
Some makers will cut in the edged before etching and final assembly and then blend out the secondary bevel using stones or sandpaper. This can be more attractive but after sharping one or two times the appearance is the same as sharpening after assembly. My personal preference is to take the blade very thin behind the edge and use a Minimal secondary bevel.
After sharpening, re-polishing and etching the blade , 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. Slide on any bolster and get epoxy under it. Next, coat the inside of the grip and anywhere the grip will contact, insert the tang onto the grip. The blade can be clamped or set in a vise to cure. Clean off excess epoxy and let set up. Once the epoxie begins to set it will peel off finished surfaces easily until fully hardened. Re-polish the grip if necessary and re apply finish. 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 steel.
- 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
- Wayne Goddard
- $50 Knife Shop
- Wonder of Knife Making
- Jim Hrisoulas
- The Master Bladesmith
- The Complete Bladesmith
Machinery Handbook – (Pub.) Industrial Press
Viking sword – Ian pearce
Records of the Medieval Sword-Ewart Oakeshott , also The Archeology of Weapons: Arms and Armour from Prehistory to the Age of the Chivalr
The sword in Anglo-saxon england- Hida Davidson