30 CFR § 33.35 - Methods of drilling; dust-collector unit.

---
identifier: "/us/cfr/t30/s33.35"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "30 CFR § 33.35 - Methods of drilling; dust-collector unit."
title_number: 30
title_name: "Mineral Resources"
section_number: "33.35"
section_name: "Methods of drilling; dust-collector unit."
chapter_name: "MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR"
subchapter_number: "B"
subchapter_name: "TESTING, EVALUATION, AND APPROVAL OF MINING PRODUCTS"
part_number: "33"
part_name: "DUST COLLECTORS FOR USE IN CONNECTION WITH ROCK DRILLING IN COAL MINES"
positive_law: false
currency: "2026-03-24"
last_updated: "2026-03-24"
format_version: "1.1.0"
generator: "[email protected]"
authority: "30 U.S.C. 957, 961."
regulatory_source: "Schedule 25B, 25 FR 6473, July 9, 1960, unless otherwise noted."
cfr_part: "33"
---


# 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.