Pitting
Small pits form on the tooth flank when the surface fatigues. The usual causes are overload, a contact pattern that is too small or too far toward the toe, and a case that is too thin. A larger contact area, a deeper case and correct setting help.
Scoring and Scuffing
Scoring is a tear of the surface caused by metal-to-metal contact when the oil film fails. Causes include too little oil, the wrong grade, high temperature and a rough surface. Better lubrication and a smoother finish, such as grinding, reduce it.
Abrasive Wear
Dust and metal particles in the oil wear the surfaces. Better seals, filters and clean oil help.
Tooth Breakage
A tooth breaks at the root when it is overloaded, hit by a shock load or weakened by a fatigue crack. A tougher core, forged blanks, a generous root radius and sizing for peak torque help.
Poor Contact
Wrong mounting distance, wrong backlash or worn bearings put the contact in the wrong place. This shortens life more than almost anything else. Setting the pair with marking compound, and checking again after the first hours of running, is cheap protection.
Reading the Pattern
The wear on the teeth tells the story. Send us photographs with your enquiry, and we will suggest changes in material, finish or setting. See hardened spiral bevel gears and ground spiral bevel gears.
