Considerations for cordless circular saw blades - effects of kerf, coating and geometry on performance?

Question

I recently acquired a low-budget ($80) 18V cordless, hand-held circular saw. The saw came with a low-budget 18-teeth ripping blade. I intend to use it mostly for cross-cutting wood planks, and cutting thin (at most 18mm (2/3’’)) plywood and laminated particleboard for making simple furniture: shelves, boxes etc. I might want to use it occasionally on other materials (plastic, aluminum), but wood and engineered wood are the main applications. I’m aware of the limitations of this tool, and I can live with a bit of sanding, if I have to.

I am looking for an optimal cross-cut/general purpose blade in order to achieve the smoothest possible cuts given the limits of this machine. The tool is very small, the maximum blade diameter is 150mm (6’’). Few manufacturers produce this blade size, so given my location and budget, my options seem to be limited to the following:

(kerf/blade thickness, no. of teeth, geometry+hook angle, “non-stick” coating, price (all dim. in mm))

More expensive: no1 (3.2/2.2, 48 teeth, ATB +15, coated, $45);

no2 (3.2/2.2, 36 teeth, ATB +15, coated, $42);

no3 (2.6/1.6, 36 teeth, ATB +10, coated, $43.5) thin kerf

Cheaper: no4 (2.4/1.4, 36 teeth, ATB +15, not coated, $21) - thinner kerf, not coated;

no5, multi material (2.0/1.4, 42T, HLTCG -5, not coated, $27) – thin kerf, different geometry

My questions are the following:

1. As far as I understand, increasing number of teeth, smaller (or negative) hook angle and larger kerf all increase the load on the saw’s motor. Should I be wary of an overload if I choose the “smoothest” blade (i.e. full kerf, 48 teeth)? Which of the factors listed above is the most important with respect to motor load/potential burning of the workpiece (kerf, geometry, hook angle, or no. of teeth)?

2. Does blade coating have a significant effect on performance (by reducing friction, which could be important given the low power of the tool)? Is this effect (and better materials) worth double the price?

3. Does anyone have any experience with ATB (Alternate Top Bevel) vs HLTCG (High-Low Triple Chip Grind) geometry? Would the negative-angle HLTCG blade result in better cuts on laminated particleboard, plywood, etc.? Is HLTCG significantly worse for other wood applications (i.e. is it specialized to composites and plastics)? Would it significantly increase loads on the motor, or does the thinner kerf of the Multi Material blade compensate for the negative hook angle?

Thanks for your input, your help is most appreciated.

Answer 1

You're overthinking this.

Presumably, the tool was designed to work with any off-the-shelf blade you might buy, and does not require any space-age coatings, specific grind, etc. Depending on the manufacturer, there is a good chance that any aftermarket blade you buy will be higher quality than the blade that came with the tool.

Of the factors you've mentioned, a thin kerf blade will make the most noticeable difference, and perhaps you will observe a longer run time of the saw between charges.

Often when it comes to blades, there is a justifiable reason for a higher price, such as carbide vs. steel (a carbide blade stays sharp longer and may last you many times longer than a steel one), or thicker carbide that can be sharpened many times vs. very thin carbide cutters that cannot be sharpened as many times (and in those cases, it is usually just as cost-effective to treat the blade as disposable).

Answer 2

Handheld (cordless) circular saws are the disposable razor blades of the sawing world. Mostly, you see them used on construction sites for rough work (trimming 2x4s and similar tasks), so the cut quality doesn't need to be all that great. A contractor is going to be more concerned with number of cuts/lifetime vs. cost, hence why you see a lot of carbide blades for construction.

Personally, I consider circular saw blades to be disposable, even if they have carbide teeth. It's often much more cost-effective to just buy a new blade than to have it sharpened. You can go to any Home Depot, Lowe's, or Menards (in the US, anyway) and get a quality circular saw blade for under $25 that will do what you want it to.

Adjust the number of teeth per inch based on the task at hand (finer tooth count for finer work, generally). The blade will say what task it's good for (i.e., rough framing, particleboard, laminate, etc.). The manufacturer knows what their blades are good for, so it's not worth second-guessing them in most instances.

As @rob says, you're overthinking it.

Answer 3

Thanks for the answers. As stated in my question, I already have a low quality blade for rough cuts. I also wanted to make finer, smoother cuts, but I was concerned that the machine would be underpowered for a blade with too many teeth or a thick kerf, hence the "overthinking". Based on input from this and other forums, I got the following answers to my questions:

1. Kerf seems to be the most important factor for cordless circular saws when choosing a blade. One should aim for a thinner kerf to reduce load.

2. Non-stick coating does not significantly affect load, because most of the blade should not touch the cutting surface (the part with the teeth is slightly thicker than the blade disc itself). It increases the longevity of the blade tough.

3. I could not find detailed answers on teeth geometry, however most people recommend using ATB geometry for general woodwork, while HLCTG is more for composites, plastics and non-ferrous metals.

Based on the above I chose option 4, (2.4/1.4 kerf, 36 teeth, ATB +15 degrees, not coated, $21).