Bit guide
How to choose a tungsten carbide button bit for your rock: button profiles, BR, BF and BD faces, Retrac and Straightrac skirts, DTH face shapes and thread systems, from the Boart Longyear catalogue.
01 Button profile
Carbide button profiles
Button shape sets penetration speed and bit life. The harder and more abrasive the rock, the rounder the button.
Rock compressive strength ranges (MPa) are from the Boart Longyear catalogue and are a starting point only.
02 Face design
BR, BF and BD faces
The face decides how straight the hole runs and how fast the bit cuts.
Recessed / drop center
Center sits below the gauge so the bit guides itself. Reduces hole deviation. Suits broken ground and straight holes in medium to hard rock.
Flat face
General purpose and easy to regrind. Hard to medium rock.
Dome face
Raised face for faster penetration, used mainly for reaming in soft ground.
- StandardStandard skirt for competent ground.
- RetracCutting edges in the skirt make the bit easy to pull back through broken or caving holes.
- StraightracAngled flutes give 360° wall contact to reduce deviation, with retrac cutting edges kept.
- Hybrid (IMPAKT)Straightrac and Retrac combined in one bit, with Raceway flushing.
04 DTH face
DTH bit faces
110 to 172 mm bits for BT4, BT5 and BT6 hammers with QL/QLX 12 spline shanks and ballistic or spherical buttons.
View bits →- ConvexPenetration first, for soft to medium rock.
- ConcaveHolds the hole straight, good in broken ground.
- FlatMedium to hard, abrasive rock. General purpose and easy to regrind.
05 Thread system
Match the bit to your rod thread
Check the thread on your rod end, or send us a photo.
| System | Sizes | Use | View bits |
|---|---|---|---|
| R | R25 to R32 | Rope thread for smaller bits, tunnelling and light production. | View bits |
| DM | DM28, DM35 | DriftMaster tapered thread, unique to Boart Longyear, holds direction in long holes. | View bits |
| HM | HM35 to HM60 | Heavy thread family for mid and large hole sizes. | View bits |
| EL | EL60 | Boart Longyear thread for the 60 mm class. | View bits |
| BE | BE58, BE68 | For shoulder drive tube systems. | View bits |
| 11° / 12° | Tapered | Push-on bits for taper rods. | View bits |
06 Reaming
Pilot first, then ream
A pilot hole is drilled first, then reamed to a larger diameter. Used for service holes and for cut holes in development rounds and drop raises.
View bits →- Pilot ReamerPilot and reamer in one piece.
- Dome ReamerDome face for reaming in softer ground.
- 6.5°Reaming bits for 6.5° collar reaming rods.
Have a part number or a worn bit?
Send it on LINE or email and we will reply with a recommendation, price and lead time.