Rockdrill button bits need periodic maintenance throughout their life to aleviate the effects of button wear. As the buttons develop wear flats, penetration rate decreases, or additional feed force is required to maintain a given penetration rate. This increases the risk of deviation and adds further stress to equipment.
To maintain close-to-new productivity and performance from the bit, the face buttons need to be re-profiled when they have developed a wear flat of about 30% of the button diameter. Gauge buttons would also benefit from regrinding as part of the bit refurbishment process.
Buttons should also be reground when “snakeskin effect” (a pattern of hairline cracks at the surface) is noticed, as this feature can rapidly progress to deep cracks and breakdown of the buttons.
Premier grinding pins benefit from years of development, refinement and field experience, providing the tool grinding craftsman with the most productive combination of grinding speed and life, to allow the drill bit to be returned to profitable use as quickly as possible.
Premier pins are available in several profiles to suit the geometry of the unworn button: hemispherical, ballistic, parabolic and conical. All profiles are the combination type, where the carbide button and surrounding steel body are cut simultaneously to provide the most effective refurbishment of the bit in a single step.
Drive arrangements are standardized to suit most common grinding machines:
• Shoulder drive with one ‘O’ ring
• Atlas Copco Terroc 55
• Sandvik Sancone A
• Plain shaft
• Adaptors are available to suit other drive geometries
Premier has developed specific matrices to give consistent self-sharpening properties for either air or water flushed grinding processes. In either case, it is important to avoid overheating the carbide and creating new stress cracks.
Various waterway configurations are available: standard (single waterway), three waterway which is better suited to provide adequate flushing to the larger sizes and twin waterway to eliminate the “nipple effect” where an uncut nib is left in the centre of the button. This effect if not corrected, can result in cracking of the button when placed back in service, due to the concentrated load in the centre. Modified single and three waterway versions are also available to effectively address the “nipple effect”.