27/64 inch in mm and decimal

27/64 in = 0.421875 in = 10.716 mm. Closest metric drill: 10.7 mm.

Taps that use a 27/64 drill

Drill	Type	Inch	mm	Difference
X	letter	.3970 in	10.084	-24.9 thou
Y	letter	.4040 in	10.262	-17.9 thou
13/32	fraction	.4063 in	10.319	-15.6 thou
Z	letter	.4130 in	10.490	-8.9 thou
27/64	fraction	.4219 in	10.716	0.0 thou
7/16	fraction	.4375 in	11.112	15.6 thou
29/64	fraction	.4531 in	11.509	31.3 thou
15/32	fraction	.4688 in	11.906	46.9 thou
31/64	fraction	.4844 in	12.303	62.5 thou

1 thou = 0.001 in = 0.0254 mm. Drills a few thou apart are usually interchangeable for clearance holes, but not for tap drills or reamer pilots.