Selecting a steel for a kanna blade.
Tsunesaburo offers a wide variety of steels in their blades, allowing them to be well matched to the material being planed.
Japanese blades are well known to be made from a thin layer of very hard
steel and a heavier main body of softer wrought iron or steel. The hard steels used in these
blades may be separated into plain carbon steel or alloyed and special steel.
Possibly the most well known and revered carbon steel is ‘Tamahagane’ more commonly known as
‘sword steel’ and has an incredible reputation, backed up no doubt by the
fearsome Samurai katana.
Tamahagane does require special treatment and also requires a significant
investment in time, resources and skill to use correctly, making it quite
unsuitable for general use. It is also very expensive, and while some tools are
made with it, they are naturally very expensive and ‘out of reach’ of those
crafts persons who simply desire a tool that works well and is affordable.
As a result, steels have been developed both in Japan and overseas better
suited to everyday blades. Many of these steels have been used in Japan from the late
19th century, and many have earned a solid reputation in their own
right. The changing needs of craftspeople has also bought about the use of High
Speed Steel where maximum edge retention is required in abrasive and demanding
materials.
◇ Carbon
steel ◇
Plain
carbon steel (white steel) is largely free of impurities making it easy to
sharpen, and will also take a very keen edge. In kanna, this steel is best suited to working with those woods that
require the keenest edge but do not prematurely blunt the edge such as
paulownia and cedar.
Capable
of being made into a fine blade that is easy to sharpen yet still quite durable
is achievable, however plain carbon steel is not as ultimately durable
as a blade made from a more complex alloy steel.
◇ Special
(alloy) steel ◇ Taking plain carbon steel and adding elements to it such as Chromium (Cr) or
Tungsten (W) increases the durability of a blade to a point where a plain carbon
steel blade cannot compare. The addition of various other elements also affects
how the steel behaves before, during and after heat treatment.
These alloy steels such as Blue steel, Super blue steel and the Swedish
steels are recommended for hard woods where improved edge life is of great
benefit, and where the keenest edge is not quite so critical. The added
alloying elements in these steels affect the grain size of the steel,
preventing them from becoming quite as sharp as plain carbon steel. While the
edge may not be quite as sharp, a usable level of sharpness is retained for much
longer.
As might be expected, these steels are a little more difficult and time
consuming to sharpen. The difference is not great, and the added time and
effort spent sharpening is returned by fewer visits to the sharpening station.
In most situations, these alloy steels are the optimal choice for plane
blades and feature prominently in Tsunesaburo planes.
◇High Speed Steel (HSS) ◇
(SKH51, HAP-40.)
These steel were developed for machining metal at such at a rate that the
tooling would become very hot, which will cause plain carbon and the previously
mentioned alloy steels to become soft. The added benefit is that these steels
have greatly increased toughness and stay sharp for significantly longer when
used in hand tools than any plain carbon or alloy steel.
Of course, sharpening is more difficult due to the extreme toughness of the
steel, but due to the fact that these steels can endure high temperatures, a
power grinder can be used for much of the work, and only a very small edge
bevel is required.
Tsunesaburo offers two choices in HSS, the commonly seen SKH51 type steel,
also known as M2 HSS and Hitachi HAP-40 Powder metal HSS (also referred to as
M4 HSS), and both are bonded (not welded) to a softer steel backing, making the
daunting task of sharpening these tough steels much easier. A unique treatment
to the back of the blade also aids sharpening ease, making what would normally
be a very difficult to sharpen blade relatively easy.
The HAP-40 powder metal HSS is unique in that the special process of making
the steel from powder allows a much sharper edge than more commonly seen M2
HSS, and also permits the composition of the steel to be improved as the
alloying elements can be increased beyond what M2 HSS is capable of supporting.
The end result is a blade that is no more difficult to sharpen, but offers even
more edge life and an increase in toughness and durability as well.
These High Speed Steels are recommended for the most demanding materials
such as very hard woods, abrasive woods and even man made wood products such as
plywood.
Steel compositions.
(Numbers represent the percentage of the given element in each alloy. The balance is iron with small amounts of additional elements/impurities.)
Steel type
| Steel name | C
| Cr
| W
| Mo
| V
|
Carbon steel
| Super White
| 1.35~1.4
|
|
|
|
|
Carbon steel
| Kawasaki Carbon
| 1.05~1.1
|
|
|
|
|
Carbon steel
| Sandvik
| 1.25~1.28
|
|
|
|
|
Alloy steel
| Blue steel #1(A)
| 1.3~1.4
| 0.28~0.3
| 2.0~2.2
|
|
|
Alloy steel
| Blue steel #1 (B)
| 1.2~1.3
| 0.3~0.5
| 1.5~2.0
|
|
|
Alloy steel
| Forged Blue #1
| 1.25~1.28
| 0.3~0.5
| 1.5~2.0
|
|
|
Alloy steel
| Special blade steel
| 1.33~1.35
| 0.72~0.75
| 5.5~5.7
|
|
|
Alloy steel
| Swallow steel
| 1.28~1.3
| 1.4~1.43
| 6.45~6.5
|
|
|
Alloy steel
| Super Blue steel
| 1.4~1.5
| 0.3~0.5
| 2.0~2.5
| 0.3~0.5
| 0.3~0.5
|
Alloy steel
| Inukubi Reigo
| 1.15~1.17
| 1.32~1.35
| 5.0~5.06
| 0.18~0.21
| 0.38~0.4
|
Alloy steel
| Togo Reigo
| 1.4~1.5
| 0.5~0.6
| 2.5~3.06
| 0.05~0.08
| 0.16~0.2
|
High Speed Steel
| SKH-51 (M2)
| 0.85~0.9
| 3.8~4.5
| 6.0~7.0
| 4.8~5.8
| 1.8~2.3
|
Powder metal HSS
| HAP40 (M4)
| 1.27~1.37
| 3.7~4.7
| 5.6~6.4
| 4.6~5.4
| 2.8~3.3
|
Carbon (C)
| Allows iron to be hardened and improves strength. Affects the ability of the steel to be forge welded. |
Chromium (Cr)
| Adds corrosion and abrasion resistance, but also increases brittleness. |
Tungsten (W)
| Improves hardness and wear resistance. |
Molybdenum (M)
| Increases toughness, durability and hardenability. |
Vanadium (V)
| Reduces the grain size of the steel, adds toughness and abrasion resistance. |
Steel name
| Soft wood
| Moderate hardwood
| Dense hardwood
| Man made material
|
Super White
| ◎ | ◎ | X
| X
|
Kawasaki Carbon
| ◎ | *
| X
| X
|
Sandvik
| ◎ | ◎ | X
| X
|
Blue steel #1 (A)
| *
| *
| △ | X
|
Blue steel #1 (B)
| *
| *
| △ | X
|
Forged Blue #1
| ◎ | ◎ | △ | X
|
Special blade steel
| △ | ◎ | △ | X
|
Swallow steel
| X
| *
| ◎ | X
|
Super Blue steel
| *
| ◎ | *
| X
|
Inukubi Reigo
| X
| ◎ | *
| X
|
Togo Reigo
| *
| ◎ | *
| X
|
SKH-51 HSS
| X
| * | △ | ◎ |
HAP40 HSS
| △ | ◎ | *
| ◎ |
◎ | Ideal |
* | Recommended
|
△ | Satisfactory
|
X | Not recommended
|
These suggested uses are a guideline only. Your experience may vary depending on the preparation of the blade and the material being planed.
Blade steel characteristics.
Steel name
| Comments;
|
Super White steel
| Produced
in a vacuum furnace, and to a high degree of purity, this steel is has a ‘sticky’
feel, possesses high toughness and excellent hardness making a very durable
blade. Improved by what is taken out rather than what is added to it.
|
Kawasaki Carbon steel
(No longer produced)
| Produced
by Kawasaki steel works in the 1950’s, it shares some similarities with white
steel in use, but allows greater sharpness. Easy to sharpen, especially suitable
for soft woods. |
Swedish steel (Sandvik & Assab)
| Produced
from high purity ore, this steel also improved by what is left out. Allows an
exceptionally keen edge with good durability and easy sharpening. Highly
recommended for medium hardwoods. Easy to use. |
Blue steel #1 (A)
| The
addition of tungsten and chromium add durability, toughness and edge life. The
most popular steel in Japan for high quality plane blades, it is stable,
reliable and predictable. |
Blue steel #1 (B)
| As for Blue steel #1 (A)
|
Forged Blue #1
| Specially
ordered steel by Tsunesaburo the 1st in the 1940’s and hammer worked
to remove forging impurities. It has a sticky feel, and is very easy to
sharpen. Especially suitable for very soft woods due to its ability to take an
especially keen edge.
|
Special blade steel
| With
the addition of tungsten as very small molecules in a significant quantity,
this steel offers improved durability over blue steel and also allows a keen
edge to be created. Light in use, suitable for moderate hardwoods, but not
recommended for very softwoods.
|
Swallow steel (Tsubame)
| This
special steel is especially suited to hardwoods, but is not recommended for
softwoods due to its need for a less acute bevel angle. Maintains its edge for
an exceptionally long time in hardwoods, has a sticky feel and is difficult to
sharpen with its high tungsten content.
|
Super blue steel
| Yasuki
steel works’ premium steel, high levels of carbon and tungsten add hardness and
strength, molybdenum allows great sharpness. Recommended for all woods. A
superior, modern manufacture steel.
|
Inukubi Reigo
| Similar
to High Speed Steel, also used for lathe tooling. Very difficult to forge and
sharpen, has exceptional durability. A unique steel specifically for blade
aficionados.
|
Togo Reigo
| Manufactured
during the early Showa (1925-1989) era by Andrews steel of the UK, now extremely rare. Suitable for all
woods. Very tough, and due to expense and rarity, suggested for very top end
users only. Performs like a blend of tamahagane (sword steel) and premium
quality western steel.
|
SKH-51 HSS
| As
used for drills and lathe tooling, has impressive impact toughness and is very
durable. Suitable for all woods, laminated materials and abrasive materials. “Uradashifuyoh”
blade back treatment allows easy sharpening. High speed grinding possible due
to high heat tolerance (550°C/1000°F) before the temper is affected. |
HAP40 HSS
| Toughest,
longest lasting plane blade steel available. Manufactured by sintering very
fine powder (6 micron). This keeps the steel’s grain size smaller and allows
additions to the alloy that cannot be made with traditional steel. Suitable for all materials, recommended for
highly abrasive exotic woods. |
