As a veteran operator, I don't just look at the floor to gauge the quality of my work; I look at the bottom of my machine. The wear patterns on the high-carbon steel trowel blades tell a detailed, forensic story about the health of the gasoline power trowel and the technique of the operator. After a long day of burnishing a hard commercial floor, I always flip the machine back onto its handles and inspect the steel.
A properly functioning machine operated by a skilled professional will show perfectly even wear along the entire trailing edge of all four blades. The steel will be polished bright, wearing down uniformly by a few millimeters over the course of a massive pour. However, if I inspect the blades and see that the outer edge of the blades is worn paper-thin while the inner edge near the spider hub looks brand new, I immediately know the operator is running the machine at far too steep of a pitch for the concrete's hardness. They are dragging the machine on its "toes," which rapidly destroys the expensive steel and leaves a washboard finish on the slab.
Even more critical is diagnosing uneven wear between the four blades. If three blades look normal, but one blade is severely ground down, I have a massive mechanical failure. This uneven wear indicates a bent spider arm or a blown thrust-collar bushing. That single blade is riding lower than the others, meaning every time the commercial gasoline engine spins the assembly at 120 RPM, that low blade is violently digging a circular trench into the floor while the other three spin uselessly in the air. Reading the wear on the steel allows me to pull a compromised machine off the slab before it ruins the grade, proving that preventative maintenance is directly tied to floor quality.
