How to prevent top hammer button bits from encountering the kind of situation in
1. Inspect Bits Frequently
Understanding the ground conditions and regular inspections of a button bit are necessary to prevent over drilling. To ensure optimal performance and life, bits require sharpening before the flat exceeds 1/3 of the button diameter. Working with a technical representative is recommended to establish specific guidelines since the maximum suggested wear before reshaping will depend on the button profile.
Drilling in non-abrasive ground can give rise to ‘snakeskin’ (small cracks) on the button surface. If it is not removed by grinding, button fatigue failure occurs.
2. Grind Protruding Inserts
Drilling in non-abrasive rock results in the bit face wearing faster than the inserts. Excessive insert protrusion, lacking sufficient steel support, can easily break while drilling and when retracting the bit from the hole. To prevent this from occurring, grind the buttons to restore the protrusion height.
3. Button Sharpening and Reshaping
If button protrusion is adequate, satisfactory re-sharpening can be achieved by use of a preformed diamond faced tool (‘cups’). Sharpening is performed by holding the tool firmly against the button and orbiting the machine in a circle to achieve a uniform surface finish. Diamond faced tools are designed to cut carbide and not steel. It is therefore recommended to have enough protrusion of the button from the face to avoid damage to the cup, bit or grinding machine.
It is always important to care for and maintain tooling and equipment. Consider a “bit” of training for drillers on getting the most life out of the top hammer button bits. More often than not, drillers come to work to do their very best and everyone wants to improve. Provide them with an opportunity to better their drilling habits by sharing these tips.