String Trimmer Line Shaping
The shape of the line also affects the cutting efficiency. String trimmer line comes in a variety of shapes: round, twisted, square, star shaped, and serrated. Rounded line is the most common type available, but it because it lacks a cutting edge, it rips the grass rather than cutting it. Twisted line is a bit better, as the shape has a little more of a cutting edge to it.
Some line comes in a square or star shape. The edges of these string trimmer lines are sharper than rounded trimmer line, and cut through the grass rather than tear at it. Serrated line is also an option when it comes to sharper trimmer line. It has teeth, similar to a kitchen knife, and saws through heavier grass and weeds with relative ease.
String Trimmer Line Thickness
This probably comes as no surprise to anyone, but the general rule with string trimmer line is that the tougher the application, the thicker the line needs to be. A larger diameter will increase the power and durability of the line, which leads to less breakage and wear-out.
String trimmer line comes in a range of thicknesses. For light work, such as trimming grass, 0.065″-0.085″ should be sufficient. For thicker grass and weeds, a line in the 0.085″-0.110″ range will get the job done, and for thicker underbrush, anything thicker than 0.110″ will work.
One note for the cordless string trimmer users: thicker strings will have an effect on your power and runtime. As the thickness of the line jumps up, more wind resistance affects the cutting head, slowing down the speed at which the engine can rotate the cutting head. Higher voltage and beefier cordless trimmers will probably be able to manage thicker gauge line more efficiently, but lower voltage models might struggle with a thicker line. Generally, it’s best to refer to the manufacturer’s recommendation for string size.