Knife/Blacksmithing course Port Macquarie Oct 19 & 20 2013

Steps involved

1. Get a piece of steel and start forging it.

Ours was a bit of an old plough. The steel was a good size for changing into a knife. It was approx 0.7% carbon content. Called 10 70 steel for this reason.

The forge was coke fuelled with an adjustable air flow valve coming from underneath. Our working temperature was approx 1300C. You need to stoke or poke the fire occasionally. Turn the air off when your product is not on the fire to save fuel. The coke needs changing when you hear the fire is not burning ideally. Do this by putting new coke on top, waiting til it catches alight and then scoop the old coke out to the side.

What is coke anyway? wiki says

Coke is a fuel with few impurities and a high carbon content, usually made from coal. It is the solidcarbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Cokes made from coal are grey, hard, and porous. While coke can be formed naturally, the commonly used form is man-made. The form known as petroleum coke, or pet coke, is derived from oil refinery coker units or other cracking processes.

From what I remember the process to get the knife shape involved flattening and lengthening our piece to the desired size. Then I think bevelling the blade edge. Then using a steel rod to create an indent approx where you want the handle to start, by belting the rod with a hammer into your knife stock. Using the horn of the anvil to create a curved grip profile in the handle section. Deciding on a point angle, I chose to forge mine with the tip slightly down. By now we sort of had the rough shape. We did cut about 2cm off the end of the handle by “hot cutting” ? Ie, chiseling this section off when the stock was hot rather than cutting it off with an angle grinder for example. In our case we had a sort of gullotine tool which could be located in the hardie hole of the anvil. The stock was placed hot into the guillotine and cut but hitting the top blade down, pinching the steel which could then be easily snapped off with tongs. Not recommended to punch all the way through and have pieces of hot steel flying across the workshop. At the end of the forging process we let our knives cool slowly in a covered tray of vermiculite, taking care to place the knives in a tip to hand lateral fashion to avoid sideways warping of the stock. We let them cool for approx 1 hour.

As far as I know vermiculite is some kind of rock thing. This grade was extremely soft with large particle size averaging about 5mm. Much larger and softer than what I have used in latex moulds or as a general filler. It seems to have a lot of applications according to wiki.

Now the forging is done.

Side factoid – When steel is glowing red hot it is no longer magnetic. You can use a magnet as an indicator to see what state the steel is in.

Step 2. rough shaping

Now using a linisher with 40 grit (?) we cleaned off the carbon scale and surface impurities. Also did the “rough” shaping of the knife. I say rough because, well, it actually didnt need that much shaping on coming out of the forge. Surprisingly, I needed up with a forged piece very close to the shape I wanted and didnt need to take off much material at all, like at most 2-3mm and nothing in some places…Probably due to the expert guidance i had with my hammer blows. The shaping process from here on would be identical to if you bought a blank stock piece instead of forging.

Step 3. heat treating (hardening/tempering)

We know moved on to the LPG forge to take our stock to an ideal temperature for hardening more accurately. This forge construction was basically a barrel shape about 50-60cm long, maybe 40cm in diameter made from High temperature insulation wool inside a steel frame. It was capped on either end with removal heat brick doors. The propane falme came from above, and also had an airflow control attachment allowing for temp adjustment. So temps could be adjusted using the regulator, the airflow falve or opening and closing the doors. We had an electronic thermometer to monitor.

For hardener we got this forge to about 800-820C and then put in our stock, in a spot where the flame was directly blasting it.

it didnt take long to heat our knives until they were an even glowing cherry red colour, about 5 mins? The next step was to quench them quickly in an oil bath (a mixture of oil, hyraulic fluid and wax, in what ratios I dont know). The quenching was done so that only the cutting edge was dipped, not fully submerging the whole knife. This was done carefully by holding the stock with tongs and gently dipping the blade in oil with a forwards and backwards motions, taking care not to go sideways as this might warp the blade. We then let our knives cool on the bench resting on their spines, not sides, so they would cool evenly.

Now that they were nice and hard they needed to be tempered to make them less brittle. This was done in a conventional oven, 1 hr at 190C, 1 hr @ 200C and 1hr at @ 210C

This was the end of day 1.

Day 2.

With all the forging and hardening done this day was all about shaping and filing, attaching the handle and sharpening.

Using the linisher and moving from 40 grit thru to 400 grit.

Im not going to write much about this but there were a few things to note.

Obviously you want to get your blade pretty well done except for sharpening before you attach the handle so you dont scratch or handle it unnecessarily. For my handle I used a timber called beefwood.

I found the shaping and sharpening of the blade by far the trickiest part of this whole process and I probably use a linisher on a daily basis normally. But I have never tried to use it to this degree of accuracy before! The blade is given its shape by, eg, holding the handle with your right hand, and the tip (with the sharp side facing up) with the fingernails of your left hand. Hold it basically parallel with your vertical linisher surface. Drag it from the start of the blade near the handle to the tip in one even motion. You want to keep it at exactly the same angle every time (whatever that is 22deg for eg). You do not want to see several sharpening facets across your stock as this will only get worse as you move up through the grits. You want to shape both sides evenly leaving about 0.5mm as the final width before the final sharpen.

This whole process is done quickly, as in not too slow across the linshing and thus building up heat (hot for your hands and bad for the tempering). But also slowly, dont rush it, practice your moves in mid air or with the linisher off so you can get those strokes in your muscle memory. You can always take more off but you cant add it back on!!!

Dont forget to constantly dip your knife in a bucket of water below the linisher every time you file to stop the heat build up. Do this before you look at the cut you have just made.

The handle is fairly straightforward. Rough cut the handle stock on the bandsaw based on your steel profile. We used some ingenious bolts called corby bolts which I have bot used before. Brass.

http://www.bushcraftozstore.com.au/products/brass-corby-bolt-14

Line up the holes squentially on the drill press so you drill one and secure it temporarily with bolt to keep the other holes in line. We countersunk the actual knife holes, mainly as a deburring action I think.

Although the bolts would probably suffice we added some 5min epoxy taking care to not get it all over your knife. After tightening and curing the bolt heads were simply sawn off on a metal bandsaw.

The handle was shaped on the linisher as well up to 400 grit. Then a coat of sanding sealer and about 3 coats of finishing wax buffed. If you have more time burnishing oil is also a good finish.

I forgot to mention when sanding the blade the typical sanding/polishing rules apply of going only in one direction until all previous grit marks are removed and then changing direction. With the final strokes being from handle to tip creating a smooth finish.

Now the knife is pretty much done. My teacher Wayne did the final sharpen on some paper sharpening wheels. Yes paper. This is the last more obtuse bevel on the <0.5mm edge you have left, and the plane you would follow for a fortnightly sharpen with a steel.

As our knives are steel not stainless i expect some tarnishing to occur over time and Wayne suggested a wipe with gumption every now and then would clean that up. WD40 would work as well but not if you plan to use the knife on food!

Good refs

http://tidewaterblacksmiths.net/2.html