The following are part of my notes from a meeting I had with a Japanese plane blade blacksmith yesterday. The subject was the type of steel to use for a replacement blade and chipbreaker for Lie-Nielson planes, and a tapered blade and chipbreaker for user-made Krenov-style handplanes. I hope you will find it interesting.
The LN after-market blades will have dimensions identical to the stock blades, but will be handforged laminated construction with an RC hardness of 63 - 64. The design of the tapered blades will be based on traditional Sheffield blades prior to the advent of metal or hybrid bodies, but with smaller slots and shorter length to better for the smaller planes promoted by Krenov.
During a meeting on Saturday April 12, 2014 with Mr. T. N., plane blacksmith living and working in Y, Japan the subject of Swedish steel came up.
Mr. N, who was apprenticed to his father and has been making plane blades for over 50 years, uses mostly Hitachi Metal’s Shirogami 2, followed by Aogami 2, as well as Aogami Super. He occasionally uses Swedish Steel and Togo steel.
Mr. N said that Kousuke Iwasaki recommended that he use Swedish Steel for plane blades, and when Mr. Iwasaki passed away, left his store of this metal to him, but Mr. N does not know the material’s designation or manufacturer (i.e. ASSAB K-120).
Mr. N said that Swedish Steel was more difficult to work than Hitachi’s products, and unless one was careful during the forging process, the material was easily ruined, the finished product would turn white, and the blade would not hold an edge. He stressed that the process of hand forging is absolutely essential to the cutting capability of a plane blade.
When I pressed him about what could go went wrong during the hand-forging process to ruin Swedish Steel, he said that one had to be very careful of the temperature, and the number of heats, because if the steel became overheated, or was heated to many times, the nature of the metal would change for the worse, probably due to carbon loss.
All high-carbon steels have this problem, but Hitachi Metal’s products are not nearly as sensitive as Swedish Steel in Mr. N’s experience. He said that, when worked properly, the Swedish Steel he used created a blade superior to any other commercially available steel. He listed the characteristics of a superior blade being: (1) It can be made very sharp; (2) It will stay sharp longer; (3) It is easily sharpened; and (4) It doesn’t chip easily.
Tokyo, Japan April 13, 2014
If you have any thoughts, please let me know, either by reply to this post, or PM.
Stan