A profile modification that eases the involute away from its true form over the top part of the tooth, usually by a few to tens of microns. Under load, teeth bend and mating teeth arrive early, so an unmodified tip would hit and scrape the next tooth as it enters mesh. Tip relief smooths load transfer, cutting noise, transmission error and the scuffing risk at the tooth tips.
Profile trace shows no tip relief at all on the reground pinion, no wonder it's screaming under load.
A gear that is quiet at light load and loud at full load usually has too little tip relief for how much it deflects.
Also heard as
- profile relief
- tip modification
Related terms
Crowning
A slight barrel shape along the tooth face so contact stays centered despite misalignment and shaft deflection.
Transmission error
The tiny difference between where the output gear actually is and where a perfect gear pair would put it.
Profile deviation
How far a tooth's actual shape from root to tip departs from the intended involute and modifications.
Scuffing
Sudden adhesive damage where tooth surfaces weld and tear apart because the oil film broke down.