Drill Bits for DTH Hammers

What are ‘Down-the-Hole’ (DTH) Drill Bits and how are they used?

Down-the-hole drill bits are used with down-the-hole hammers for drilling holes through a wide range of rock types. Our drill bits are designed with a splined drive for rotating the bit in the ground. Drilling bits are available in a range of different sizes and configurations so they can drill a wide range of holes sizes, in different ground conditions.

We guarantee to have a drill bit that can tackle any challenge

It is crucial that you choose the right drill bit for your DTH hammer to save costs and time.  We pride ourselves on having a comprehensive range of drill bits for DTH hammers so you can be sure that you will definitely find a suitable drill bit for any project you are undertaking. Our carburised drill bits are the best in the world, providing outstanding performance and durability.

We produce all our drill bits at our specialised plant where they are made out of high quality nickel chrome alloy steel. They are carburised and heat-treated to offer extra protection against wear and fatigue. Every hole in the bit head is machined to within microns and fitted with carbide inserts which provide the cutting action of the rock.

We have three different bit heads: Flat Face, Concave and Convex. These are available with three different inserts: domed, ballistic and semi-ballistic inserts. We guarantee that we have a drill bit that can tackle any challenge and rock face formation.

Head Designs

Flat Face

Alternative design for all rock conditions especially fractured and fissured rock and changing formations.

Concave

Alternative design for all rock conditions particularly deep hole drilling: can improve hole alignment as a result of inverted pilot.

Convex

Strong design for all conditions, especially hard abrasive rock. Good balance of fast drilling and long service life.

 

Inserts Types

Domed Inserts

Strong rugged shape for high performance and good service life in all conditions, particularly suitable for very hard abrasive rocks and deep hole drilling.

Ballistic Inserts

Suitable for soft and medium compact low abrasive rocks producing large cuttings.

Semi-Ballistic Inserts

Suitable for all soft and medium rock conditions including fractured and fissured rock.

 

How have DTH Drill Bits developed?

The first type of drill bit used with down the hole hammers was a “cross bit” design. Four chisel shaped lengths of tungsten carbide were brazed into the bit body. The action of brazing preset stresses within the drill bit thereby limiting its life. A further disadvantage of the cross bit was that the majority of the carbide was situated around the centre of the bit face and not towards the outer edge of the drill bit where there is the most rock to cut.

In the late 1960’s the button bit was introduced. This was a landmark in the progress of DTH drilling equipment which led to bit lives previously unheard of. The button bit design eliminated the primary shortcomings of the cross bit. Cylindrical button inserts are precision ground to extremely close tolerances and pressed into the drill bit as an interference fit. This resulted in improved carbide insert retention by eliminating brazing stresses and other defects associated with brazing and braze materials. Button inserts are distributed more efficiently than cross bit inserts by providing more cutting power where it is needed at the outer edge of the drill bit face.

The need to sharpen the drill bit was eliminated with the arrival of the button bit and the improved cutting action provided increased drilling rates particularly in hard rocks. Whilst the cross bit design is still used in some rotary and drifter applications where the rock is very soft, the button bit is now used in virtually every DTH hammer.