The numbers 1095, 1060, 1050 represents the type of steel used on our blades. The carbon content of the steel is expressed as a ‘point’ of carbon. Each point signifies that 0.01% of that steel is carbon. For example, a 45 point steel will contain 0.45% carbon. Steels with carbon contents lower than around 40 points (0.4%) WILL NOT HARDEN MEASURABLY. The table below shows some uses for different carbon-content steels.
5-10 points: Nails, wire. Not hardenable.
10-20 points: General use. Not hardenable.
20-30 points: Screws. Some machinery parts.
30-40 points: Machinery parts. Will harden slightly.
40-50 points: Gears, Axles. Will harden.
50-60 points: Crowbars. Tools. Will harden enough to take a good edge.
60-70 points: Swords, axes, cleavers. Chopping blades.
70-100 points: Cutlery. Knives. The lower range of this bracket is used for tougher blades, the upper range for hardness and a longer lasting edge.
We will only discuss here the type of steel used on our blades which is plain carbon steel 10XX.
The Xs refer to points of carbon. For example, 1095 is a plain carbon steel with 95 points (0.95%) carbon; 1060 has 60 points (0.6%) carbon; while 1050 has 50 points (0.5%) carbon. The higher the carbon content of a blade, the tougher/harder the blade is and will have a longer lasting edge.
Since our 1050 series only has a 0.5% carbon, it is only recommended for kata or suburi and for cutting light targets such as water filled bottles and single roll of tatami or beach mats. It is not recommended to cut hard targets such as fresh green bamboo as it will surely roll its edge, blunt or even nick the edge.
Our 1060 series has 0.6% carbon and will harden enough to take a good edge. Recommended cutting targets are water filled bottles, double roll of tatami or beach mat, and occasional cutting of fresh green bamboo. Frequent cutting of hard targets will eventually dull the edge and sharpening will be needed.
Our 1060 Series is also capable of taking a 45-degree bend and still returning true, which provides practitioners an ample leeway for a less than perfect cut. You can watch the video below:
Our 1095 series has 0.95% carbon, which is very close to the carbon content of tamahagane (steel used in Japan for making nihonto) that has 1-1.5% carbon. Our 1095 line is suitable for heavy cutting (frequent cutting of fresh green bamboo with a diameter of 2.5-3 inches) as it has a longer edge retention. Heavy cutting doesn’t necessarily mean you can cut anything with it. Cutting of trees/tree branches are better left for axes, cleavers, machetes.
If you want your katana to last a very long time, take good care of it and only cut recommended targets.
To explain the 1st and 2nd digits:
The Society of Automotive Engineers (SAE) has established standards for specific analysis of steels. In the 10XX series, the first digit indicates a plain carbon steel. The second digit indicates a modification in the alloys. 10XX means that it is a plain carbon steel where the second digit (zero) indicates that there is no modification in the alloys. The last two digits denote the carbon content in points, see above.
Source: Classification of steels
About T10 tool steel:
The “T” stands for High-Speed and the “10″ means there is between 0.95% – 1.05% carbon. These types range from the T1 which is between 0.05% – 0.15%, All the way up to T15 which is between 1.20% – 1.30% carbon. Tool steel are primarily used to make tools used in manufacturing processes as well as for machining metals, woods, and plastics. They are generally ingot-cast wrought products, and must be able to withstand high specific loads as well as be stable at elevated temperatures. It is a high speed tool steel that gets extremely hard on the surface but remains springy in the center. Other properties include extremely high abrasion resistance which should mean it will keep its edge longer and resist scratches.