Large diameter button bits need to have some different characteristics to those of our intermediate range to enable them to meet the different drilling conditions that are generally encountered as hole sizes increase. The blow rate gradually decreases but the energy of the blow significantly increases.
These large diameter bits are produced from a high carbon steel and heat treated to withstand the very heavy piston blows that they are subjected to as the size of the DTH hammer increases.
All button bits in these larger diameters are generally only available in a flat face design and buttons are all round or hemispherical. To provide extra protection, gauge buttons are fitted to the larger diameter bits.
Large diameter bits to suit Bulroc hammers are supplied with nylon drive plates, designed to minimise metal to metal contact between the splines of the bit and the chuck.