The ASTM D217 test in which a standard 150 g cone is released into a grease sample at 25 C and the depth reached in 5 seconds is read in tenths of a millimetre. Unworked penetration is taken on the grease as received; worked penetration follows 60 double strokes in a grease worker and sets the NLGI grade. Prolonged working to 10,000 or 100,000 strokes shows how far the grease softens under shear.
Worked cone penetration came back at 340 on an NLGI 2, that grease has gone soft in service.
Also heard as
- worked penetration
- pen
- penetration
Related terms
NLGI grade
Number from 000 to 6 describing grease stiffness, based on cone penetration after working.
Grease
Semi-solid lubricant made of oil held in a thickener sponge, usually with additives.
Soup
Grease that has broken down or been mixed with an incompatible type and turned runny.
Thickener
Solid structure in a grease, usually a metal soap or polyurea, that holds the base oil like a sponge.