This guide is intended as a reference for buying modern Japanese swords, as my knowledge of pre-modern and antique swords is limited.

     Buying a Japanese sword is complicated enough; buying one on eBay can be twice as complicated. Why? Because if you buy a sword in person you can get a feeling for the seller - you'll have more to go on to know if the seller can be trusted. You'll also be able to handle the piece and see it's condition and quality. So why buy a sword on eBay? Because you can get one heck of a deal if you take your time and shop!

1) Know your seller! This is very important. Check your sellers feedback carefully, be cautious of any seller with a feedback under 98% unless there's one helluva good reason for it, ie; sickness that kept the seller from meeting commitments for a period, but the feedback is otherwise good. If you see more than a few negative or neutral feedbacks that complain of non-delivery or that the item was not as described, you're probably in the wrong place to buy a sword. Contact the seller if you have any questions about him or her, or about the item. You can learn a lot from the response - or the lack of one.

2) Know what you want the sword to do. If you want a display sword and have a limited budget, don't waste your time looking at hand forged functional swords. If you plan on using the sword for tameshigiri (cutting practice with a live blade), or if you just want a display sword but want it to be the real deal, get a good hand forged sword. I recommend a carbon content not less than .45% for a functional sword.

 3) Blade material: There are three basic blade materials for modern Japanese style swords, these are; steel (commonly called carbon steel), stainless steel, and non-steel alloy (commonly called alloy). I'll do my best to explain what each one is and what it's good for.

     Steel:  Commonly called carbon steel - which is redundant - all steel by definition contains carbon. Steel is simply iron with carbon added. The carbon makes the iron stronger. Period. There's nothing magical about carbon steel. Here's a breakdown of the various types of "plain" carbon steel and what they're good for:
 
Plain Carbon Steels

     These steels are iron, usually (but not always) with less than 1 percent carbon, plus small amounts of manganese, phosphorus, sulfur, and silicon. The characteristics of these steels are primarily a product of carbon content, although the alloying and residual elements do have a minor influence.

Plain carbon steels are divided into four groups:
1. Low
2. Medium
3. High
4. Very high

Low. Often called mild steels, low-carbon steels have less than 0.30 percent carbon and are the most commonly used grades. These steels are too soft to hold an edge, and would be easy to bend with use. Some display swords are made from mild steel. I'd prefer stainless because neither is fully functional and stainless looks better.

Medium. Medium-carbon steels have from 0.30 to 0.40 percent carbon. Increased carbon means increased hardness and tensile strength, with decreased ductility. These steels are too soft to hold an edge, and would be easy to bend with use. Some display swords are made from medium carbon steel. I'd prefer stainless because neither is fully functional and stainless looks better. Carbon content of .40% is an important threshold; steel with a carbon content of .40% or greater can be hardened, below .40% it cannot be hardened.  

High. With 0.45 to 0.75 percent carbon, these steels are capable of sword quality hardening, can hold an edge well, and make a good sword. Remember that a sword is not just a big knife. A functional sword will be subjected to stresses that a good knife has nightmares about!

Very High. With up to 1.50 percent carbon content, very high-carbon steels are used for high quality knives but generally not for swords.

     The lowest carbon content usually found in functional swords is .45%, and this would be called 1045 carbon steel. The highest carbon content commonly found in swords is .95%, and this would be called 1095 carbon steel. The "10" that precedes the percentage indicates that it is plain carbon steel. Another prefix you might see is "51", as in 5160 steel. The "50" family of prefixes indicates the chromium content, and is usually used in manufacturing springs, but also makes an excellent blade.

     Generally, the higher the carbon content, the higher the price. Lower carbon steels are easier to sharpen, but don't hold an edge as well.

Stainless Steels

     There are many types of stainless steels which fill a variety of roles. For the purpose of this discussion, there are four basic types. All of them contain varying degrees of carbon, manganese, chromium, and vanadium, as well as a few other ingredients. It is the quantities and ratios of these ingredients which give each type its characteristics. It should be noted that although a very high quality functional knife can be made from stainless steel, it is impossible to make a fully functional sword from stainless. There are some stainless swords that can be used for Aikido, Iaido, and kata, but a stainless sword should never be used for tameshigiri; it will either bend or break, and usually on the first swing.

     Here are the four types commonly used in swords and their general characteristics:

420, 420J and 420J2: Quite soft and not very rust resistant. Very inexpensive and easy to grind, so lots of cheap swords can be made very quickly. Swords made from these steels should do nothing but hang on the wall; even swinging one could break it.

440A: Soft but extremely rust resistant. Treat these swords as you would one made from 420 steel; it will look better than 420 steel, but will be very prone to bending. You could probably store a 440A sword in salt water and not have it rust; good quality diving knives are made from 440A.

440B: Harder than 440A, but less rust resistant. A good quality sword made from 440B can be used for Aikido, Iaido, or kata if the blade is thick enough and the tang is long enough (it doesn’t have to be a full tang, but it should be at least eight inches long and not be a rat-tail), but won’t be suitable for tameshigiri. Again, good quality diving knives are often made from this type of steel.

440C: The hardest and least rust resistant in the 440 family. These are the most functional stainless swords, but still can’t be used for tameshigiri.

     Swords marked “440” not followed by an A, B, or C are usually A or B. Contrary to popular belief there is no such thing as “plain 440”.

There are other families of high quality stainless (such as ATS-34) that are used for knives, but not for swords, so that will be the topic of another review.

Non-steel alloys

     These swords fall into two main categories: 1) Iaido swords that are made in Japan, and, 2) Low quality swords, usually an aluminum alloy that aren't worth your consideration.

   Japan has very strict laws about how swords are made and which swords can be exported. One of these laws says that functional blades capable of cutting can only be exported in very limited numbers, and only under certain conditions, which is bad if you live outside Japan and want to own a Japanese made sword. Although Japanese made swords can be found on the market, they are rare and expensive.

     As a result of this, Japanese factories produce alloy swords that cannot be sharpened and therefore can be exported without restriction. These swords can be used for Iaido, Aikido, and kata.

4) Types of forging and blade construction: There are three basic types of Japanese sword blade that can be built by forging:

Simple: Also called monosteel. The blade is made from one piece of unfolded steel. Very simple and effective. Most high quality swords are made like this.

Damascus: A folding technique where the steel is folded over itself many (generally up to sixteen) times, leading to hundreds or even thousands of layers (one fold = 2 layers, two folds = 4 layers, three folds = 8 layers, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, etc.). More folds than sixteen are pointless, as the layers would become thinner than one molecule - which is impossible. This method was developed to remove impurities from the steel (it also removes carbon, which is bad, but can be compensated for to some degree), but modern steel is so pure that Damascus folding is no longer needed. It is now used primarily for aesthetic reasons; Damascus steel looks really good; you can see the layers in the blade.

San Mai: Translates to "three layers". Layers of softer, lower carbon steel (or iron) is forge welded to layers of harder, higher carbon steel. The lower carbon steel forms the core (and sometimes the sides and/or back), and the higher carbon steel forms the edge. The hard edge will hold its sharpness, the softer core provides shock absorption; making the sword harder to break. Unlike Damascus, San Mai is still very practical. San Mai folds should be invisible unless revealed by etching; if you can see a San Mai fold the forge welding was flawed and the blade should be discarded - you'll have to trust your seller that the blade is San Mai - you usually can't tell by looking. San Mai can be revealed by etching the blade with acid, such as ferric chloride, but I don't recommend trying this unless you know what you're doing; you can permanently stain the blade. San Mai swords are more durable (and more expensive) than simple blades. They are more durable (and usually less expensive) than Damascus blades. A blade can be either San Mai or Damascus, or it can be both; Damascus steel which is then San Mai welded. Very cool, looks good and lasts long.

5) Types of heat treatment. There are three basic types of heat treating in Japanese swords:

Untreated: Simple, there is no heat treatment. The least durable and least functional type of sword blade.

Homogeneous, or "mono" heat treatment: The blade is treated uniformly and has the same hardness all over. These swords can be both fully functional and fairly inexpensive. I recommend this type of swords as a first functional sword till you know if you will maintain interest.

Differential heat treatment: The edge is made harder than the back of the blade. This makes the edge very hard with excellent edge retention, while the softer back gives the blade flexibility, toughness, and shock absorption. A differentially hardened San Mai blade will be very durable and have excellent edge retention, I recommend this type of sword for intermediate to advanced practitioners.