D & L Thomas Equipment offers many different types of drill steel. Made from high-grade steel, drill steel is used in rock drills and dowels and is created when low-carbon steel is fused together with either charcoal or cast iron. Drill steel is also called by other names such as jack hammer steel, drill rods, and sinker drill steel, and it is available in many sizes from R25 to T51 and even H-Thread.
Tips on Drilling
1. Be Prepared
- Experienced, skilled drill operator
- Avoid improper bit handling, i.e. carbide against carbide damage
- Drill rig properly lubricated
- Sufficient drilling accessories on hand
- Keep accessories clean and free from damage
- Striking face is square and true
2. Starting the Drill
- Firm footing for the drill
- Align and collar the hole properly
- Begin slowly and adjust the feed and throttle as the bit buries
- Maintain enough rotation for good penetration
- Excessive rotation will wear the gauge
- Maintain correct feed pressure;
- Insufficient air pressure leads to a loose drill string and premature wear
- Sufficient air pressure is ideal to keep the bit from bouncing on the bottom
- Too much pressure will buckle and bind the steel in the hole
- Over feeding in hard rock will reduce penetration
- Over feeding in soft rock can lead to burying the bit and hanging the steel
4. Clean Hole
- Blow the hole frequently when drilling deep
- Soft of muddy ground can seep causing the steel to hang up
- Blow with every drill rod added below the hole, preventing a plugged steel
5. Drill Dieseling
- Occurs with insufficient feed pressure
- Also happens with full throttle when withdrawing the bit
- Dieseling heats up the drill and burns off the lubricant
- Results could include a destroyed hammer
- Stop dieseling by reducing the drill throttle and increasing feed pressure
6. Changing Bits
- Try to follow a larger bit with a smaller bit
- Try to use new bits with new steel
- Use lubricant on bits, as well as couplings and steel threads
- Remove bits with a bit wrench or "rattle" loose, no beating with a hammer
Common Drill Steel Failures
Failure Type 1 - is characterized by a fatigue rose originating from the surface. It can occur on both round and hex steels anywhere along the length of the rod.
Failure Type 2 - is characterized by a fatigue rose originating in the bore, and can occur anywhere along the length of the rod.
Failure Type 3 - is typically a sudden failure, no fatigue rose being present, through the radius where the threads meet the rod section (either round or hex).
Failure Type 4 -
- Occurs where the coupling ends and is typically a sudden failure.
- Occurs about 1/3 the way into the threads and is associated with worn threads and surface galling.
- Is a chip broken off the end of the drill steel.
|Cause of Failure||Most Likely Reason||Possible Reason|
|Type 1||Surface damage caused by hammering or careless use of drill steels.||Galling against the side of the hole. Surface defect in steel. Severe overfeeding.|
|Type 2||Corrosion originating in bore, accelerated by high stress conditions.||Internal defect in steel, e.g., an oxidized inclusion.|
|Type 3||Wandering or drifting hole. Severe overfeeding. Misalignment of drill feed.||Worn threads and/or coupling. Migrating couplings (occurs when bridge wears out).|
|Type 4 (a)||Severe overfeeding or other cause of heavy sideloading, as in Type 3.||Badly worn or migrating coupling.|
|Type 4 (b)||Worn threads. Fatigue through the surface stress raiser.||Worn coupling (similar to position 8 on the striking bar).|
|Type 4 (c)||Drill steels improperly joined in coupling (e.g., worn or non-spec bridge in coupling).||Drill rod end broken or not cut off true.|