Basics of Japanese saws

Basics of Japanese saws

In this issue, we write about TPI, blade thickness, kerf width, and Asari. We are sure you know some of them, so please read only what you are interested in.

What is TPI?

TPI is used to describe the fineness of saw teeth. TPI is how many teeth per inch (25.4mm).

The finer the teeth (higher TPI number), the cleaner the cut surface will be. Conversely, the rougher the teeth (smaller TPI number), the faster the cut will finish, but the rougher the cut surface will be.

Blades for cross-cut generally have a higher TPI number, while those for rip-cut have a smaller TPI number. Both are the result of the design to cut wood smoothly.

*Finest teeth for cross-cut
Dozuki 8” for Kumiko / TPI: 30

*Roughest teeth for cross-cut
Kataba 10.5”, Ryoba 8” / TPI: 14

*Rip-cut blade of Ryoba 9.5” / TPI: 9

About blade thickness

Japanese saws have thinner blades than Western saws. Since Japanese saws are designed to cut with a pulling motion, they can cut even with thinner blades.

The thin blade is delicate and can be easily bent if force is applied when pressing the blade. Always please be careful to apply force only when pulling.

*Thickest blade
Kataba 10.5” / Balde thickness: 0.024” (0.8mm)

*Thinnest blade
Dozuki 8” for Kumiko / Blade thickness: 0.008” (0.2mm)

About kerf width

The kerf width is also narrower related to the blade thickness. The benefits of narrow kerf width are as follows.

・Remove minimal wood and produce less sawdust
・Need less power and with less tiredness
・Can cut longer and more accurately
・Suitable for precise and complicated woodworks

What is Asari?

"Asari" is the saw's teeth alternately opening slightly outward. We think it is called a "set" in English. It makes the kerf width slightly wider than the blade thickness when cutting wood. This reduces frictional resistance and makes cutting easier. Also, sawdust can be easily scraped out.

The flush-cutting saw has no Asari. Therefore, you can cut only dowels without damaging the work surface.

*Flush cut saw 5”
Blade thickness = Kerf width: 0.012” (0.3mm)

*Flush cut saw 7”
Blade thickness = Kerf width: 0.008” (0.2mm)

Understand the features of Japanese pull saws and use them correctly to enjoy woodworking!

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