Gritty, Notchy, Notchy/Springy, Bumpy bearings, whats the diff?
While on the subject of not so good feeling bearings, lets agree on a couple of terms. Gritty: a bearing that has contamination such as dirt or grit, (PTFE solids fall into this category) in the lube. Can cause balls to lock and skid and could cause flat spots on the balls. Can usually be solvent cleaned and eliminated. Notchy when out of the part: usually caused by flat spots on one or more of the balls. This can be from lack of lube, skidding caused by contamination, and as in the case of main shaft bearings, high impact load such as blade to ground strike or a even a boom strike. This can put a flat spot on the ball. And of course there are other causes -poor material used for the balls and races, etc. Cannot be salvaged by cleaning/greasing. If it is notchy after thorough cleaning and re-lubing -trash it! Can cause mild to severe vibration. Notchy/Springy when in the part: When the part is moved slowly, the part will “spring” back or ahead at certain points of slow rotation. Caused
