Building Nathan Fosters Hunting Knife
This page documents the construction of a bowie style hunting knife in CPMS35VN for Nathan Foster of Terminal Ballistics Research in New Zealand
Nathan Foster is the principle of Terminal Ballistics Research; a New Zealand based business that was formed to educate hunters and shooters worldwide. This is delivered via his extensive online cartridge knowledge base, tutorial books, hunting tutorial services and rifle accurizing services (including self learning via bedding products and tutorials). The TBR website is recognized internationally as an information resource that provides useful and meaningful research that is firmly grounded in genuine, in-field experience. The site currently receives over 100,000 new visitors per month.
Here’s a link to the TBR website homepage. http://www.ballisticstudies.com/
I visited the TBR site personally many times when I was choosing and developing my own hunting kit and also read a number of Nathan’s books. I found the information so valuable that I made and gave him a knife as a personal gift of thanks. Later I also made him a field bowie, to his design, out of 52100 carbon steel. The initial idea was to compare the carbon steel to one made from high-end stainless, by testing them in the field during Nathan’s numerous hunting trips. However for various reasons the stainless version didn’t materialise. Until now ! Following recent (June 2017) chat on the TBR forum I’ve asked to donate another field bowie in CPMS35VN stainless to the cause. The installments below will document the building of this knife and hopefully, later on, include some pics of it being used in the field. I will also put some of the more significant photos on my Instagram account; warrick_at_riflebirdknives
The story will unfold from the top of this page downwards, so start reading at the top and scroll down for more updates.
This is the drawing supplied to me by Nathan. All measurements are approximate and to act as guides for me rather than dictates.
A couple of points I’d like to make before we start;
Firstly, call me a design snob, an artistic Nazi, whatever, I’m not a fan of the traditional bowie profile, for no other reason than I don’t like its aesthetic. However having watched some of Nathan’s videos, showing the way he uses his knives in the field, I understand where he’s coming from and will endeavour to meet that need.
Secondly, I never and I mean never, make a knife to specific drawings. This is because as an artisan I like to have creative control, the client has to throw me a bone by letting me add my creative whims here and there. I’m not a factory and I’m doing this for the pleasure of it. That being said, in the name of our experiment I want to eliminate as many variables as possible and will do so by meeting the brief as best I can.
Personally, I’m looking at this drawing and thinking the handle is too short, I’d like to add another 10mm to the length, especially if a lanyard hole is to be included on the lower butt. Otherwise lets go !
The steel: CPMS35VN is a premium stainless steel made by Crucible USA. It was designed and is aimed specifically at the high-end cutlery market and according to the data sheet should demonstrate improvements in what’s called ‘toughness’. In the knife making game toughness refers to the ratio of hardness/edge-retention/brittleness/wear resistance. Unfortunately, due to some inconvenient laws of nature, they can’t all be high at one time, there are trade-offs and the ideal result is the best compromise you can wrangle from this mix. Here’s a link to the Crucible data sheet for this steel. CPMS35VN You may also like to Google around the ‘custom knife world’ for commentary. Warning, this will all be opinion (of course). One thing is for sure, this gear does rank up there for plain martensitic steel, coming in at around $300/m for raw bar 4.5mm x 50mm at the time of writing.
With the bar of steel cut to length, I print and cut out a paper copy of the plan. This is marked onto the steel (left) and then a rough grind of the outline is made (right) What does this process look like? Well you can follow the link below to a short video on my Instagram account. You have to press to start. To come back here, just use your return arrow.
The profile is then refined with some more delicate grinding and the use of traditional elbow grease and hand files (left), then checked against the plan (right)
In preparation for grinding the bevels into the blade a centre line is marked on the cutting edge and spine of the blank. For the cutting edge, the grinding process will endeavour to come close to this line from each side, leaving a 1mm wide “landing” that will later accommodate the cutting edge itself. The line on the spine allows me to judge and centre the distal taper, which will extend from the start of the clip to the tip. I also mark two parallel lines on the handle section in preparation for tapering the tang.
Tapering the tang. Why? Well, mainly to minimise weight. This is a sizeable knife and steel stacks on weight quickly with length, so any savings are valuable, something that will gain in importance with every step you take toward the end of a long day in the field.
The red device is a strong magnet with 25kg of pull. The tapering process starts with putting the butt against the grinding belt and removing steel until I reach the parallel lines. I then progressively lean forward, pushing the taper up the tang toward the ricasso. The end effect is an even taper from the butt to the ricasso, which is then repeated on the other side.
It is vitally important that the tang remains dead flat during the tapering process. Otherwise the handle material will show ugly gaps and a lack of tolerances. Here’s where patience, practice and skill come to the fore. I check it regularly against a straight edge, hold them up to the light and if there are any gaps, it’s back to the grinder to slowly refine and refine.
The tapered tang. The taper is flat and even on both sides, meeting the parallel lines at the butt. That’s a lot of steel-weight removed but don’t worry, there’s still much more there than you could bend with use.
I suppose I should mention that a flat, no gaps, tapered tang is also a demonstration of skill that knife makers will flaunt on occasion. Yep, the equivalent of a posing pouch at a body building contest. It does take time and it is one of those extra yards we travel.
Grinding the plunge bevels, removing the metal along the length of the blade to make it, ….well, a blade.
The full process took around two hours. You’ll be happy to know that while there is plenty of video to watch, I abbreviated what you get to see substantially. If anyone wants to watch the full two hours they can contact me and we’ll arrange a screening at a cinema near you.
You’ll note I’m wearing gloves. I’m also wearing good quality ear-muffs, have safety glasses and a dust extraction system. The gloves sport thick slices of saddle leather taped onto the thumb pads. These are to insulate my thumbs from the hot metal, mainly during the 60 grit (green belt) phase. Check out my coat. They aren’t tears on the belly where my verandah has contacted the grinding belt, they are burns from when I grind carbon steel. I sometimes get lost and absorbed in the moment and don’t realise that the shower of sparks has set my coat on fire. “What’s that burning smell, oh $%$@#@, it’s me!” Yes, I have set the house fire detectors off once.
There are also small lengths of mild steel super-glued to each side of the knife just in front of the tang. These give me leverage, allow me to easily torque the blade into the belt, cutting edge first. Without them I might accidentally destroy the thickness of the spine. (Happens in a blink and then it’s back to hacksawing off another length of steel bar).
During the grinding process you’ll notice I stop quite regularly and turn the knife around in various directions. This is not for your benefit, it’s me checking progress. A little at a time and steady as she goes, always checking, always checking.
After the main bout of grinding has been completed. Here’s a close up of the scribe line we put down the centre. This photo shows the bevel grinds from each side have met evenly, leaving around 1mm width of metal, forming what’s called a landing. This landing will be the focus of the two much smaller bevels that create the actual cutting edge. Making the cutting edge is the very last thing done to the knife, just before it’s shipped to the client. That’s the best way for me not to cut myself….
Hand sanding the blade. This takes a couple of hours but ensures the flats are uniformly flat. There is also a significant aesthetic component here, getting all the ‘brushed’ strokes aligned in a meaningful direction, in this case parallel to the length of the blade. I start with 400 grit and then, for this knife, finish with 800 grit. No doubt I’ll have to repeat some of this work when the knife comes back from heat treating but it’s good to get as much work done now as possible, while the steel is still relatively soft, that is, just normal ‘steel hard’.
The second photo is me stippling the ricasso, just done for looks.
Ready for heat treating. All drillholes are made, the hand sanding is finished and brushed look is established, the ricasso is stippled. Also, you’ll notice I’ve been through with hand files and tidied up all the curve radiuses, squared off the spine, finger guards and butt. Note how the tapered tang looks and how the distal taper extends from the start of the clip to the point. Lastly, I put it in a vice and flex it this way and that, making sure it’s dead straight when looking along the spine, we don’t want any bends along the length from tip to butt.
Heat treating is where the hardness is raised significantly from ‘normal’ steel hard to ‘knife’ steel hard, otherwise it won’t hold an edge for very long. Side effects are also benefits. Hardened steel is springy, so it’ll bend and then come back to its original shape. The steel also gains wear resistance. Simply, this hardening is not ‘case hardening’. Rather, it involves soaking significant heat right through the steel long enough for molecular changes and, in this case, air quenching in aluminium blocks or similar to freeze those changes in place. The steel is then tempered to relieve stresses and take away some of the brittleness that hardening brings.
Unfortunately, this is also where we have to let our project sit for a wee while. I need a batch of at least five knives to submit for HT, so it’ll have to wait until there are four more ready to go.
Here it is, making part of a batch off to heat treating.
You’ll note the surfaces of the back three haven’t been finished off to the same extent as the front two. They are going to be coarse-grit sand blasted after HT, so they’ll end up with a frosted look.
The black G10 composite handle material has arrived. The first process is to grab a texta and crosshatch the side that will attach to the tang. Then, using a figure eight motion I sand it flat on a sheet of 80 grit that has been taped to a square of 10mm thick float glass. Keep doing this until the texta marks are all gone. Even better, if you hold the scale up to a strong light you can’t see a gap between the flat surface and a straight edge resting on it. Has to be as flat as you can make it so there is no movement between the handle and the tang in service. This takes time but is very much worth the effort.
Left image shows sanding the brass rod that will be cut to make the handle pins. Roughing it up so it has some teeth during the handle glue-up.
Right image shows the same treatment being given to the tang of the knife. Well scratched with some 50 grit
Why pins? As you are aware, glue has great tensional strength, can lift a tonne with one drop etc. However it is not so strong if given a lateral shock. The pins are there mainly to strengthen against sideways hits. They also provide a pathway that links one side of the handle to the other, making for a solid sandwich.
here’s all the handle materials ready to go. It’s important to note which pins (cut from the brass rod seen being sanded in the photo above) are front and back as they are different lengths due to the tapered tang. The front set are longer than the rear set. The fat brass at rear is a lanyard tube. I mark the paper towel to make life easy for myself.
The tapered tang creates and angle between it and the vertical drill bit. To make sure I’m drilling perpendicular when setting the pin holes I have to tilt the drill press table by the inverse of this angle, normally a couple of degrees. I use a digital inclinometer, accurate to within a tenth of a degree, to set this up. The procedure is then reversed for drilling the other side of the handle material.
One side of the handle material is clamped onto the tang and drill holes made. As each drill hole is completed its corresponding pin is slotted into place, insuring there is no movement during the rest of the procedure. I run the drill on a relatively slow speed, around 400rpm to minimise heat and tear out, backing out often to clear the hole. These man made fibre materials will last forever on a knife handle but will warp if cooked, thus ruining all that hard work we put into flattening them on the sanding glass.
Time to drill the other side. Note the drill table has been tilted to correspond to the change in angle of the tapered tang. Also, the first set of scales drilled is now on top and the undrilled set is on the bottom. Thus the first set now acts as a template for drilling the second set. Here’s a tip to aspiring knife makers, never drill the second set without the first one attached, it’ll end in tears I can tell you.
Push a couple of pins through to the tang and hold it in place relative to the rest of the existing holes. Then as soon as new holes are drilled right through both sets of scales, put pins in them as well. Lock everything and stop as much movement as possible.
Left. Once the holes are drilled, remove the knife and pin the two scales together. The shape of the front, the leading edge of what would be the bolster, is then cut into both scales. The bolster face is then sanded smooth, right down to 2000 grit, because once the scales are attached to the knife there is no access to this portion of the handle.
Right, hand sanded and polished.
Left. The handle material is cut from the rectangular roughly to shape and all the bits are laid out prior to glue-up. I like to be organised during this phase because it’s a gloopy, sticky business at the best of times.
Right. An old sheddies trick, put Vaseline on the surfaces of your clamps so they don’t get glued to the job. Man, has this one shed-hack saved me a lot of heartache.
The glue-up is done. All the pins are rolled and dunked in glue and put in place, the inside surfaces of the handle scales are fully smeared in glue. After the clamps are fixed in place I then take some time to clean up the squeezed out glue on the ricasso, which is the metal in front of the bolster. Easier to do this now than after the glue has set.
I use a special two part mix called Megapoxy made by Vivacity Engeneering. It’s supposed to be good to go after 24hrs, however I leave it for three days because the next phase of work does generate frictionaly heat and sideways torque, so I want it to be as set as set can get.
The post-it note is because I often have more than one on the go, so to avoid confusion etc.
This is what it looks like straight out of glue-up. Nothing pretty about that mess and those squeezed out wisps of glue, the ones that look all soft and creamy, are as hard as stone so quite sharp and just a little bit deadly.
Here’s me shaping the handle. I use a large belt grinder to rough in the coarse shape. It’s mostly explained during the video so you don’t need me to write it up here.
After coarse shaping on the grinder, I take it to the bench and hand sand in some final contours. I go to the finer grits and get rid of all the ugly scratches, nicks, divots and generally tidy the handle and tang’s metalwork up.
Left, I use a drill to remove the build up of set glue inside the lanyard hole.
Right, more hand sanding, this time softening some of the edges where I know fingers will rest. Look carefully at the peak of the thumb rest and you’ll see I’ve put in a slight chamfer.
Here’s the finished knife. The handle has been through some more mucking around to get to this stage. Firstly, as above, it was sanded and made into a usable shape. However, I found that even at a relatively coarse 800 grit the G10 was too slippery. I debated chipping just the apex of each side but eventually decided to have the handle sand blasted. This looked great but was still too slippery. So, I’ve put a random chip all over and sand blasted it, and…..it’s much better. Gloved or wet hands should be able to find some purchase and grip. The only place I didn’t chip was inside the finger guard, that’s left smooth because I thought texture there would be irritating.
Anyway, the handle is finished and overall, the knife is a bit of a beast.
So that’s it, the knife is now in Nathan’s hands and being put to use in the field. This page didn’t cover my making the leather sheath, maybe I’ll do that kind of thing at another time.