[Code of Federal Regulations]
[Title 30, Volume 1]
[Revised as of July 1, 2002]
From the U.S. Government Printing Office via GPO Access
[CITE: 30CFR33.35]

[Page 158]
 
                       TITLE 30--MINERAL RESOURCES
 
  CHAPTER I--MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR
 
PART 33--DUST COLLECTORS FOR USE IN CONNECTION WITH ROCK DRILLING IN COAL MINES--Table of Contents
 
                      Subpart C--Test Requirements
 
Sec. 33.35  Methods of drilling; dust-collector unit.

    (a) General. All drilling shall be done with conventional, 
commercial drilling equipment--pneumatic-percussion, hydraulic-rotary, 
and/or electric-rotary types--in accordance with the applicant's 
specifications.
    (b) Pneumatic-percussion drilling. A stoper-type drill with a piston 
diameter of 2\1/2\ to 3 inches shall be used for roof drilling, A hand-
held, sinker-type drill with a piston diameter of 2\1/2\ to 3 inches 
shall be used for down drilling and also for horizontal drilling, except 
that the drill shall be supported mechanically. Compressed air for 
operating the drill shall be supplied at a gage pressure of 85-95 pounds 
per square inch. Drill bits shall be detachable, cross type with hard 
inserts, and shall be sharp when starting to drill each set of 10 holes. 
In roof drilling, 1\1/4\- and 1\1/2\-inch diameter drill bits shall be 
used; in horizontal and down drilling, 1\3/4\-inch diameter bits shall 
be used. The drill steel shall be \7/8\-inch hexagonal and of hollow 
type to permit the introduction of compressed air through the drill 
steel when necessary to clean a hole during drilling.
    (c) Rotary drilling. A hydraulic-rotary drill with a rated drilling 
speed of 18 feet per minute free lift, capable of rotating drill steel 
at 900 revolutions per minute with 100 foot-pounds torque, and having a 
feed force of 7,000 pounds, shall be used for roof drilling. An 
electric-rotary drill, supported by a post mounting, with a rated 
drilling speed of 30 inches per minute and powered by a 2.25 horsepower 
motor, shall be used for horizontal drilling. For roof drilling, the 
bits shall be hard-tipped, 1\3/8\ and 1\1/2\ inches outside diameter, 
and 1\1/4\-inch auger-type drill steel shall be used. For horizontal 
drilling, the bits shall be hard-tipped, 2 inches outside diameter, and 
1\3/4\-inch auger-type drill steel shall be used. Drill bits shall be 
sharp when starting to drill each set of 10 holes.