The initial period of operation, often in steps of increasing load, during which roughness peaks and small errors on new tooth surfaces wear or plastically flatten, improving contact and the oil film. A good run-in lowers the risk of early scuffing and micropitting. The first oil fill is often drained afterward to remove the wear debris it collected.
Run-in at half load for the first eight hours, then dump the oil and change the filter before full production.
Also heard as
- break-in
- running-in
- wear-in
Related terms
Fuzz
Shop word for the fine metallic paste that collects on a magnetic drain plug from normal gear wear.
Scuffing
Sudden adhesive damage where tooth surfaces weld and tear apart because the oil film broke down.
Hard gearing
Shop term for case-hardened, ground gears, as opposed to through-hardened soft gears that are cut to finish.
Worm wheel
The gear driven by a worm, with throated teeth that wrap around the worm, usually made of bronze.