PROCEEDINGS of the HUMAN FACTORS SOCIETY 33rd ANNU! MERING-1989 KNURLS ON POP BOTTLE LIDS

Do knurls improve torque capability? A "pop-bottle " size lid (28 mm diameter, 15 mm high) was varied with six designs: 1) a smooth lid, 2) a lid with 13 knurls/cm, 3) a lid with 7.9 knurls/cm, 4) a lid with 3.9 knurls/cm, 5) a lid with 3.9 knurls/cm but for only 4 mm of height, and 6) a lid with 2 protrusions ("radiator type"). The 18 subjects rotated each lid. Using the smooth lid torque of 1.49 Nm as loo%, the lid with 7.9 knurls/cm had 170%, the radiator type had 164%, the 13 knurls/cm had 163%, the 3.9 knurls/cm had 141%, and the 3.9 knurls/cm for only 4 mm had 110%