I've been working, learning to forge weld with the intent of making some laminated blades. For me, one of the biggest attractions of the Japanese tools is the blades. Ultra-high carbon steel, laminated to a backing of soft iron........It's not a JUST a Japanese tool thing. Laminated blades work soooooo well!
Big, thick plane blades contribute mass, making the actual cutting edge of a blade more stable. This helps to reduce edge flexation (is that a word?), which can causes a blade to chatter when planing. Thick blades make for a broad bevel surface, which increases stability when hand sharpening. Very thin ultra-high carbon steel can be heat treated to an incredible hardness, but by itself is useless. Pair the thin cutting steel to a thick soft backing, and you get a tool that gets incredibly sharp, but is still (relatively) easy to sharpen. And, Laminated blades LOOK cool! Mono-steel edges seem so bland, for lack of a better word.
I am a firm believer in copying from those who know better, so I am learning how to stick high carbon steel to low carbon iron. No wrought iron yet, but hopefully soon. My source for high carbon steel is the perennial favorite of the backyard bladesmith, old files.....sometimes referred to as type O-F steel (Old File, get it?).
The true composition of the steel used to make files is generally guessed at being 1095, a simple carbon steel with around 0.95% carbon content. 0.95% carbon is pretty high and will make for a very hard edge, exactly what you want for a file, right? It gets more interesting.
I have found some references that Nicholson (a large American manufacturer) may have used a higher carbon, special steel of 1.22% carbon. This steel is also use to make very hard taps and dies, and other high performing tooling. So a file might be made from 1095, or possibly 1.22% special steel.... What other options are there?
That was back in the day. Today, a file can be made from any number of alloys, especially now that manufacturers are outsourcing to international suppliers. The new Nicholson files (made in mexico) have been developing a bad reputation for being soft and wearing out quickly. So, something has changed, some standard has been relaxed to maximize profit. Poor quality control? Cheaper materials? Focus group determines that rust resistance is more important to consumers than ultimate hardness? Products can change, practically overnight.
I have a super cheap set of small detail files that I bought from Walmart a couple of years ago. I think that I paid about $6.
These files have been used hard and, frankly, put my old american made files to shame. These are incredible! I bought one set, and liked then so much that I went back to buy another. A few months later, I tried to buy a set to give to a friend but, to my great dismay, they were gone. Not out of stock, just gone. I still have a hard time getting used to the transitory reality of the global marketplace. Another few months passed.....back on the shelf. The second batch was as good as the first, I just hope that they stay that way.
I forgot to add..... Although I have broken two of these files, I haven't worn out ANY of them, and they see a lot of use! These are every bit as durable as my old swiss Grobet needle files, and maybe better. Certainly cheaper, and easier to source. These will make some great carving tools, maybe this winter.
These are a generic Chinese offering. There is no brand identification of quality, no intent to build customer loyalty. These are made to be inexpensive. Walmart sells other files, too. Those new (bad) Nicholson files? Here is where they are found. Brand loyalty has turned into a sad joke. It's our own fault. It's my fault for buying based on price.
Years ago (before globalization) you could go to a store and maybe have one choice to make. Buy "the best", or buy the cheaper "good enough" brand. Often a manufacturer would open a second line of tools, maybe more expensive, under a different name and targeted to a different demographic. Think Chevy and Cadillac.
Money is hard to get so, generally, we buy the least expensive option. The "cheap" manufacturer sells more tools, is more profitable, and soon buys the smaller "better" company. Now, the "better" company has brand value and a loyal customer base, but they need to make more money...... You can see where this leads.
Now, you go to the store, say Walmart again, to buy a drill. There are six different brands. The price spread is fully represented, from cheap to expensive, but none of the offerings are really any good. All of these brands are owned by Stanley/Black and Decker, but sold in different packaging essentially. This is survival of the fittest. Twenty different options, none of them good. Home depot is no different. I shop there, too.
My cheap China files are great. These (also generic China) files, on the other hand, are total crap.
I bought these at a different store, $4 each. I suspect that they are case hardened mild steel. They make lousy files, and even worse knives. They can't be heat treated. What a waste of packaging. They have a lifetime warranty! Full replacement, you pay shipping, haha!
To harden simple carbon steel, you heat the metal to around 1,500° F, then quickly cool it within a period of time, typically measured in seconds. This sets the crystalline structucture of the steel in an arrangement that is very rigid, hard essentially. More than just hard though, we want the steel to exhibit a fine gain structure, and the grain size is affected by the heat at which we quench the steel at. Higher heat makes for a large grain size. Large grain size is brittle, and won't produce a sharp, durable edge.
To determine the optimal quenching temperature for a given steel, I need to experiment. That means breaking stuff.
So, I've got lots of little pieces steel to practice welding with. What I have been doing is seeing if I can stick these different types of metal together. Some combinations just naturally adhere well. The O-F steel forge welds to mild steel very well. Mild steel to mild steel is giving me some difficulty. Spring steel to spring steel is tough, too.
Anyways, I'm not trying to actual MAKE anything, I'm just sticking stuff together randomly, fold and stick, fold and stick. Insert random scrap of metal, fold it again and weld it. Cut and polish the sample to check the quality of the welds. For me, the key to proficiency is experimentation and familiarity, so I am doing lots of welds, but not trying to make things nice..... so don't judge to harshly, haha!
I found a use for the non-hardening file steel. Bend the metal lengthwise into a U-shape, then weld a small piece of REAL steel into the void. A san-mai marking knife..... My first laminated blade!
You know how it is when you just slap something together and it's total crap, but it's too nice to throw away? I etched the blade with ferric chloride to darken the high carbon steel. The division looks like a differentially hardened hamon (like a samurai sword), but it's actual the lamination boundary. Pretty cool.
I also made a chisel shaped object. Now I can test my heat treatment, and gauge edge durability. Edge tool abuse! The chunk of wood is an old piece of Red Oak.
I've never hammered a knife into a chunk of wood before, but this little blade is remarkably durable. It's probably a good thing that I am a total novice, using junk steel and iron age technology. This leaves a lot of latitude for luck. I didn't take any real precautions to refine the steel (normalize) before hardening, and just applied a thin clay wash to the blade before performing a water quench.
I am pleasantly surprised, amazed really, at how well these blades are performing. The edges are as sharp as any of my Japanese chisels, yet are easy to sharpen. I think that this particular file steel is comparable to the basic Yasuki white steel (1.20-1.30% carbon) used for most Japanese chisels. These turned out harder, and take a better edge than many of my real Japanese chisels, so I am cautiously optimistic. I would take more care if I was trying to actually make something. This was just experimenting.
This little chisel shaped object made for some interesting tests of durability. I slapped the file steel into place, but then bumped it before setting it permanently, so the cutting edge is only 75% hard steel. Sloppy, but interesting.
I took no care, hammered straight down into the oak, as though cutting a mortice. Many times. I pried the waste with less caution that I would use with a real tool.
The back side is REALLY ugly. The vertical black line (that looks like a crack) is the lamination boundary. The blunt part on the left is the mild (unhardened) part of the edge.
The steel held up very well (better than expected) but the unhardened part just folded, as it should. The cutting edge isn't magic, it didn't shave the steel from my anvils edge. I tried, but the edge chipped a tiny bit, then was easily resharpened. It didn't make for a good photo.
I hammered the faux chisel into a section of mild steel rod.
Penetration 1/16", 5 hammer blows. I've never done that to a chisel before. Well, not intentionally, that is....
You can see the faintest evidence, right in the center, but it's mostly due to the iron rod burnishing the darkly colored (oxidized) steel cutting edge.
I expected the edge to shatter or, at the least, to crumple or chip. No damage, and still shaving sharp.
Not too bad for an old file.