Page 577 - Air and Gas Drilling Manual

Air Hammer Bit Shank Passage
The air hammer bit shank passage has an inside diameter of 1.4375 inches and a
length of 11.0 inches. Thus, the inside diameter of the shank passage, D sp, is
.
d sp 1 4375 inches Chapter 11: Specialized Drilling Equipment 11-15
d sp
D sp
12
D sp 0 120 ft
.
The length of the shank passage, L , is
sp
.
l sp 11 0 inches

l sp
L
sp
12
L sp 0 917 ft
.
Over the length of the bit shank passage the surface roughness is
e p 0 00015 ft
.
With the above, Equation 6-73 becomes

2
1
f isp 0 120
.
2 log 114
.
0 00015
.
.
f isp 0 021
Equations 6-67 and 6-68 become, respectively,

.
10
a isp
53 36
.
a isp 0 019
.
and