What is Kerf?


What is precisely the term Kerf on a circular saw blade???

The Oxford dictionary states the following: from Old English Cyrf; West Germanic origin to carve.

In present day German the word Kerben is translated as notch &/ carve.

Whilst most blades are described as having a kerf of X number of millimetres; in truth a kerf is the cut &/ notch left by the cutting implement (blade in our case). How important is the kerf on our blades then?

For most of us, it has very little if any significance unless you are specifically looking for a set size.

The wider the kerf also means a thicker blade body,thus a stronger blade. Cutting tips are usually approximately 0.2mm wider than blade body so as to provide clearance & let the blade carry on through it’s path.

However manufacturers do make blades with ultra narrow kerfs; usually approximately 1.6mm for a 160/165mm diameter, which means the blade body must be in the region of 1.4mm thick or less ( now that’s very thin, which equates to being more prone to flexing). If you plan on using an ultra thin kerf blade, you’d be well advised to take some precautions in order to avoid doing yourself a mischief. For a start using the saw in a guided set up such a guide rail for portable hand held machines (thus avoiding side movements) &/ in a table saw where the blade is rigidly fixed onto the arbor of the machine & the material is usually guided towards the blade or mitre saw where the blade is rigidly held in a sliding carriage over the material.

Cutting thinner materials so as to reduce excessive strains on the blade body. Thinner blade bodies do not dissipate heat as well as thicker ones, but due to their physical thinness will be more sensitive to buckling (deformation) once heated, so a shallower depth of cut is preferable.

If processing expensive materials such American Black Walnut for example, then the use of a thinner kerf blade can be fully justified, or if the material is severely rationed & you have to complete a project with what is readily available. A thinner kerf could mean the difference between being able to finish a project if multiple cuts are necessary.

The main advantage to a thinner kerf blade is that it requires less horse power to drive it through the material. The thinner the kerf, the less material is being removed (therefore less wastage) thus less power needed. I can see that a lot of you are thinking, this will do perfectly for my cordless saw (more linear cuts per charge right?). Unless you are highly skilled in using a portable hand held circular saw free hand; I would strongly recommend using a guiding set up of sorts & restricting your cutting frenzy to thin materials.

A blade with a thicker kerf would be preferable for most purposes, not to mention that by it’s very physical size will be more rigid & therefore more able to stand up to abuse & still remain true when cutting. By the same token a wider kerf requires more horse power to drive it through the material. Most modern machines have ample power, so this becomes less of an issue, except more saw dust generated. The kerfs vary according to the diameter of blades & from manufacturer to manufacturer but you’ll find there is very little difference in general for a specific size.

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