A thin coat of colored paste or fluid, either Prussian blue or a yellow or white gear marking compound, applied to the teeth of one gear before the pair is rolled together. Where teeth touch, the compound is wiped off or transferred, leaving the contact pattern visible. It must go on thin and even, or the film itself hides the true pattern.
Put a thin coat of bluing on the gear, roll it both ways under a little drag and let's see where it's touching.
Also heard as
- marking compound
- Prussian blue
- gear paint
Related terms
Contact pattern
The imprint left on gear teeth by marking compound after running, showing where and how the teeth touch.
Set the pattern
Shop phrase for adjusting pinion depth and backlash on a bevel or hypoid set until the contact pattern is right.
Heel and toe
The outer, wide end (heel) and inner, narrow end (toe) of a bevel or hypoid gear tooth.