HSS 18% Planer Knives: Why Are There Differences in Quality?
When looking for HSS 18% planer knives, jointer knives or thicknesser knives, it can be tempting to assume that all knives sold under the HSS 18% designation are identical. Same dimensions, same HSS 18% specification and same intended use: on paper, the differences may appear minimal.
In reality, the quality of a planer knife does not depend solely on its dimensions or on the HSS 18% designation. The quality of the steel, its composition, heat treatment, grinding process and cutting-edge preparation can all influence its performance and service life.
At Probois Machinoutils, our main supply consists of ILMA HSS 18% planer knives. When certain sizes are temporarily unavailable from ILMA, we may also source knives from MFLS Forézienne. In this case, the origin is clearly indicated on the product page so that customers know which manufacturer is being offered.
What is an HSS 18% planer knife?
HSS stands for High Speed Steel, a family of highly alloyed tool steels particularly well suited to the manufacture of cutting tools.
For planer, jointer and thicknesser knives, the HSS 18% designation is traditionally associated with high-speed steels containing a high proportion of tungsten, particularly the HS18-0-1 grade, corresponding to T1 type steel.
This grade contains approximately 18% tungsten, together with elements including chromium and vanadium. Combined with suitable heat treatment, these alloying elements provide characteristics required for cutting tools, including hardness, wear resistance and the ability to maintain cutting performance.
This is precisely why this type of steel is particularly suitable for manufacturing planer knives, jointer knives and thicknesser knives used for woodworking.
Why can two HSS 18% planer knives be different?
Two knives can have exactly the same dimensions and both be marketed as HSS 18% planer knives, yet still have differences in manufacturing quality.
The grade of steel is only one part of the equation.
Heat treatment is essential to achieve the required mechanical properties. Grinding accuracy affects the geometry of the knife, while the quality of the bevel and the preparation of the cutting edge directly influence cutting performance.
For this reason, two HSS 18% knives may show visible differences in finish and may also behave differently during use and successive sharpening operations.
Our choice: ILMA HSS 18% planer knives
Our choice is based on one simple objective: to offer a genuine, consistent-quality HSS 18% planer knife, rather than selecting a product solely on the basis of price.
The quality of a planer knife depends on several factors:
- the actual grade of steel used;
- its alloying-element content, particularly tungsten in HS18-0-1/T1 type HSS 18% steel;
- the heat treatment and resulting hardness;
- the dimensional consistency of the knife;
- the quality of the bevel grinding;
- and the final preparation of the cutting edge.
A properly manufactured genuine HSS 18% steel is particularly suitable for planer and thicknesser knives because of its wear resistance and its ability to maintain an effective cutting edge. T1 steel containing approximately 18% tungsten is indeed used industrially for the manufacture of planer and jointer knives.
For these reasons, whenever possible, we favour ILMA HSS 18% planer knives for our range.
What does our photo comparison actually show?
We wanted to photograph two HSS 18% planer knives from two different manufacturers side by side.
This comparison is useful because it makes it possible to observe certain differences directly, particularly in the surface finish, bevel grinding and cutting-edge finish.
However, an important distinction must be made: the colour or external appearance of a steel cannot be used to determine its chemical composition. A photograph alone cannot therefore determine the amount of tungsten contained in a planer knife.
It can, however, highlight differences in manufacturing and finishing between two products intended for the same application.
This also illustrates why the HSS 18% designation should not be the only criterion used when comparing two sets of planer knives.
Why is the cutting edge of a planer knife so important?
On a planer, jointer or thicknesser fitted with conventional knives, the blades rotate at high speed and remove a small amount of material with each pass.
The quality of the planer knife cutting edge therefore has a direct influence on the machine's performance.
A correctly prepared cutting edge contributes to a clean cut and an even surface finish. As the edge gradually becomes blunt, cutting resistance increases and the quality of the finish may deteriorate.
The ability of an HSS planer knife to retain an effective cutting edge is therefore an important consideration, particularly for regular users.
Is a cheaper planer knife really more economical?
The price of a set of planer or thicknesser knives should not be considered solely at the time of purchase.
The length of time the cutting edge remains effective and the number of times the knives can be correctly resharpened should also be taken into account.
A cheaper knife that requires more frequent sharpening may ultimately cost more in use. There is also the time required to remove the knives, have them sharpened and, above all, correctly set the planer knives after refitting.
This is why we prefer to focus on consistency and manufacturing quality rather than systematically looking for the cheapest planer knives available.
Why do we sometimes offer MFLS Forézienne knives?
Our preference for ILMA does not mean that every size is permanently available from this manufacturer.
We offer a wide range of planer, jointer and thicknesser knife sizes, and occasionally an ILMA reference may be temporarily out of stock.
In some of these cases, we may source the required size from MFLS Forézienne so that we can continue to offer our customers the planer knife they need.
We have chosen to be transparent about this: when the knife supplied is manufactured by MFLS Forézienne, this information is clearly stated on the product page.
Customers can therefore check the origin of the product before placing their order.
This allows us to maintain the availability of a large number of knife sizes without suggesting that they all necessarily come from the same manufacturer.
ILMA remains our preferred supplier
Whenever the required reference is available, our preferred choice remains the ILMA HSS 18% planer knife.
This choice is not simply based on the brand stamped on the knife. It reflects our aim to offer consistent and clearly identified HSS 18% planer knife quality, suitable for use on planers, jointers and thicknessers.
We believe that a cutting tool as important as a planer knife deserves more consideration than simply choosing the lowest price.
The knives are directly responsible for cutting the wood, so their quality has a direct influence on the results obtained when jointing or thickness planing.
How to choose planer, jointer or thicknesser knives
Before ordering replacement planer knives, the first step is to check the exact dimensions of the original knife: length, width and thickness.
Compatibility should never be determined solely from the machine brand. The same machine model may have been produced in different configurations depending on its year of manufacture.
The steel quality should then be selected according to the intended use. For many common woodworking applications, HSS 18% planer and thicknesser knives provide an excellent solution thanks to their wear resistance, cutting performance and ability to be resharpened.
What should you remember about HSS 18% planer knives?
Two knives carrying the HSS 18% designation should not necessarily be considered strictly identical. The final quality depends on the steel used, heat treatment, grinding accuracy, bevel geometry and cutting-edge preparation.
At Probois Machinoutils, we favour ILMA HSS 18% planer knives for our regular supply. When we occasionally offer an MFLS Forézienne product because an ILMA reference is unavailable, this is clearly stated on the product page.
We believe this transparency is essential. In addition to dimensions and the HSS designation, our customers should also be able to identify the origin of their planer knives and make an informed choice.
A good planer knife is not defined solely by its dimensions or the HSS 18% designation: steel quality, manufacturing accuracy and the cutting edge all make a difference.