
Drill Sizes  Lettered 
Drill bits are available
in hundreds of sizes, and the size designations include letters, numbers, decimals, and fractions. Decimal drill
sizes further include both SAE units and metric units. This particular page presents the lettered drill size
series. RF Cafe also has drill size tables for
numbered drill size
varieties.
These drill bits are almost always of the twist type that advance through the material being
bored by turning in a clockwise direction as viewed from the top. They are said to be righthand drill bits.
A 
0.234 
N 
0.302 
B 
0.238 
O 
0.316 
C 
0.242 
P 
0.323 
D 
0.246 
Q 
0.332 
E 
0.250 
R 
0.339 
F 
0.257 
S 
0.348 
G 
0.261 
T 
0.358 
H 
0.266 
U 
0.368 
I 
0.272 
V 
0.377 
J 
0.277 
W 
0.386 
K 
0.281 
X 
0.397 
L 
0.290 
Y 
0.404 
M 
0.295 
Z 
0.413 



