So, riding my bicycle to work this morning, I had a bogan fuckwit yell abuse at me and try to run me off the road.

So what, you say? Happens all the time, get over it.

Well, yes, I am somewhat used to this sort of thing. What really got me this time, though, was that not 15 minutes later, at an intersection, there were two police units pulling cyclists up for failing to dismount before crossing via the pedestrian crossing.

What a great use of resources. A highway patrol car and a motorcycle, sitting there slapping cyclists over the wrists for cycling, instead of walking, across a signalled pedestrian crossing. Meanwhile bogan fuckwits are free to try and kill cyclists unworried by inconveniences like law enforcement.

Yet another example of the fucked up state of police powers and priorities.

To celebrate Pi day, I made pi(e)! It is a pumpkin pi(e) (recipe here) I made using pumpkins harvested from the pumpkin vine that has taken over our back yard.

Yum!

I recently purchased a lansky rod based sharpening system, as found here. Overall, it seems to be a great sharpening system, although there are a few caveats.

First off, the good.

It comes with 5 sharpening stones, from extra course to ultra fine. Extra course works really well for grinding a new bevel angle, with the rest getting progressively finer to allow nice polishing of the edge. The jig allows you to get consistant angles on both sides of the blade without having to re-attach the knife when swapping sides. This makes it really easy to get a razor sharp edge, and to re-grind edges to your preferred angles (for example, a 20/25 double bevel, which should give decent sharpness and decent durability).

Here’s a picture of it in use

Note the 4 holes for different angles.

(the knife pictured is my “smithing” folding knife – bought from a chinese ebay seller for around AU$25 delivered. supposed to be a high carbon non-stainless steel, with a 58-59 RHC. Build quality was poor – liner lock did not lock, and hinge bolt had crappy torx sockets which stripped in no time. After repairing the liner lock by re-grinding the edge, and cutting slots in the hinge screw to allow the use of a flat blade screwdriver, all is good now. The blade seems to hold an edge well, and it is reasonably solidly constructed)

In use, I start off with a course or extra course if I need to regrind the bevel. Grind one side until you can feel a bevel form on the opposite side. This means you’ve ground that edge down until it meets the other bevel, giving a thin edge. Once this is done, swap sides and grind away until you feel another bevel on the other side. Now, go to the next finest stone and repeat the same process. What this is doing is polishing the edge, allowing a finer edge to form as you go to finer grit abrasives. Once you get to the finest abrasive, you will need to remove the burr by lightly grinding the other edges. You want to break off the burr, while not forming a new burr. Pretty easy once you get the hang of it.

Now onto the not so good aspects. While the angle guides allow you to get consistant angles, they are not accurate. To describe why, we’re going to have to do a bit of basic trigonometry.

If height is the hole used, angle is the desired edge angle, and then length is the distance the blade edge is from the jig. Here’s a rough overlay which may help illustrate it:

Where we run into problems is that length is in fact variable. Imagine that the next time I go to sharpen that knife, I clip the jig right on the edge of the blade, effectively increasing length. What that does it changes the angle (making it smaller, or shallower). While I will still get a consistant angle, it will be different from last time, meaning that edge properties will be different, and I may need to grind away a lot more steel than I otherwise would have.

To try to combat this, I’ve started noting down the position of the jig on each knife blade a sharpen. This way I should get it reasonably consistant each time, which should help. For example, with the pictured knife, i line the jig up against the thumb stud, with the front lip of the jig about in line with the edge of the main blade bevel grind.

The next issue is the accuracy of the angles. Given that the angle varies depending on how far out the edge is, the marked angles have been made with a certain measurement for length. I assumed that this would have been a couple of centimetres past the lip of the jig, where you would expect most blades would sit. However, doing the maths, it turns out that for the given angles, the blade would actually have to be about a centimetre behind the lip of the jig.

What this means is that the indicated angles are actually larger than the real angles you will get. The wider the blade (that is, the further the blade edge is from the jig), the smaller the angle will be. So, this means if you’re sharpening a meat cleaver with a 10cm wide blade, then angle (for a given indicated angle) will be much smaller than if you’re sharpening a pocket knife.

So, does this mean it’s not worth using this system? No.

It still allows you to get consistent edge angles and razor sharp blades, and do this quite easily and quickly. You can calculate exactly what angle you will get if you want to. Otherwise, just bear in mind that actual angles are less than indicated, and perhaps use the next angle up instead. If you want to get precise angles, then something like the Edge Pro system would work well, but this is going to cost. I’d like to build a system like this at some point, but that will have to wait for the rest of my projects to be done!

I finished making my first knife today, a sheepsfoot (lambsfoot?) chisel ground knife. I’ve been reading a lot about steel and heat treatment lately, so i thought I’d put it to test, and making knives seemed like a nice functional way to do it.

This first knife started life as an old wood chisel I found when I moved into this house. I snapped the handle off one time when i was pretending that it was a cold chisel, so it’s just been lying around. Seems as it started off life as a chisel, i thought it would be appropriate to give it a chisel grind.

I started out by annealing it to soften the steel to a level which I could work. Initially I tried this in a fire, which worked to an extent, but i found it was a bit uneven, with the handle end significantly harder than the tip. I tried this again using a butane blowtorch. Surprisingly, I was able to heat the entire blade to a dull red glow, then I slowly bought the temperature back down by reducing the flame and time it was applied to parts.

Once this was done, using an angle grinder, I ground the sheepsfoot shape, then the blade bevel. Rough shaping of the handle was done using the grinder, then I moved onto a half round file to shape the handle. The flat side of the half round was used to tidy up the blade bevel.

Two handle holes (3mm) and a lanyard hole (5mm) were drilled in the handle. I then cleaned up the metal surface, using a sharpening stone (the hardware store two sided style), then 320 and 800 grit went and dry. The surface still has some arc shaped scratches from the initial grinding with the angle grinder.

I then heat treated the blade, by heating with a butune blowtorch till a dull red glow was achieved, holding it at that temperature for about 2 minutes, then quenching in used engine sump oil. Tempering was then performed by heating with a blow torch until the black coating started to smoke.

I think I’m going to re-do the heat treating and tempering, as reading further indicates that I think I should have held the steel at a high temperature for longer (15 minutes or longer) to allow dispersion of alloying elements, which would lead to better carbide formation. I believe the tempering should have also been done with more heat and for a longer duration, but I will research this further. While I’m at it, I’m going to try to remove the scratches to see if i can get a better polished finish from the blade.

For sharpening, I used my Lansky rod sharpener (reviewed here) to grind a “30 degree” chisel edge. This means it is flat on one side, with a 30 degree bevel on the other. a 30 degree included angle (compared with a 20 or 25 degree bevel on a normal knife, which gives a 40 or 50 degree included angle) should give it a very sharp edge. The downside to such a sharp edge is that it shouldn’t last as long as a dual bevel. Accounting for the high hardness of the steel, I figured this should be ok.

I really noticed the difference in steel hardness sharpening this knife. Compared with other knives I’ve sharpened with the Lansky (such as a cheap chinese knock off gerber folding knife, supposedly with a 440C blade and 56-58 RHC) the steel was much more resistant to grinding, and when burrs formed, they were much harder to remove. So far, the edge seems to maintain near shaving sharpness after cutting through woody branches and stalks, so I’d say it’s a fairly tough edge.

I started out intending to make scales from some scrap 3mm aluminium sheet, but I opted for a cord wrapped handle instead. Mainly due to laziness (cord wrapped is much easier to do), but I do thinkg that it is probably more suitable, as a thick handl would look out of place on a such a small blade. The cord I used for the wrapping is 2mm hoochie cord.

Overall, I count this as a great success for my first knife making experience. Sure, it’s a tiny knife, but I’ve still found it useful harvesting pumpkins and trimming plants. The thickness of the blade (about 2.1mm) means it is not so good for cutting through things, but that’s not that big an issue for a small knife like this. The next task is to make a sheath for it. I figure I’d like to make one in a neck knife style. I think my heat treatment and tempering also needs some improvements. While this one appears to have turned out ok, I think it could certainly be improved next time.

I’ve got some knife sharpening to do, and have come across some useful resources in my research, on sharpening and blade materials:

http://forums.egullet.org/index.php?showtopic=26036

http://users.ameritech.net/knives/

http://www.sff.net/people/pff/steel.txt

A quick summary of the important points for me are:

- 440C stainless is a good choice for blade material
- a 15/20 degree double bevel is a good choice for kitchen knives. adding a few degrees to each bevel increases durability, so perhaps 17/23 might be a better choice for a pocket knife.
- bevel angle is measured from a centreline running through the centre of the blade – actual edge angle is twice the bevel angle, since you have a bevel on each side.
- the aim of sharpening is to make the edge as thin as possible – fixed angles make this more predictable. You can tell when you’ve got a thin edge when a burr forms.

A very detailed resource on steel grades and their performance in knife blades:

http://cutleryscience.com/reviews/blade_materials.html#S_AUS4A

Also interesting reading are the following articles on knife making. I have some old files and chisels which I might experiment with.

http://www.hossom.com/tutorial/jonesy/

http://www.primitiveways.com/pt-knives-1.html