Helpful Drilling Tips

  • Check drill string to avoid early bit failures when using worn drill pipe, stabilizers, deck bushings and/or shock subs.
  • Inspect hoisting jacks, do not lose horizontal position whilst drilling.
  • Use a quality thread grease and ensure that the shoulders of the bit and drill pipe are coated to prevent galling.
  • Flush the drilling assembly with air before screwing on the bit.
  • When making up the rock bit use slow rotation and ensure that the drill string and rock bit mate properly shoulder to shoulder, monitoring carefully in order to avoid cross threading.
  • Choose the correct nozzle sizes. Ensure that the minimum recommended air pressure (35-40 psi, 2.4-2.8 bar) is maintained in the drill bit. Note that cab pressure gauges can read significantly higher than this value. As a rule-of-thumb: the difference between cab and at the bit is 8-10 psi (0.5-0.7 bar).
  • Bit cones should be checked periodically to be sure that all are about the same temperature. Uneven cone temperature generally indicates that the air passage to that bearing is obstructed. Clean the bit with water and continue drilling.
  • All new drill bits should be broken-in at reduced weight and rotation speeds to ensure that all working surfaces are run-in and slightly work hardened prior to applying full operating load. In general, following these recommended guidelines should maximize bit life:
    • Drill at 50% of normal weight and rotation for the first 10 minutes (or for the first rod in a multi-pass operation).
    • Drill at 75% of normal weight and rotation for the next 10 minutes (or second rod).
    • Drill as normal (100%).
  • Always use low feed force and a low rotation speed when collaring a new hole. Always use a minimum amount of water to reduce dusting.
  • Turn the air on just before lowering the bit to the ground to begin collaring the hole. Keep the air on until the bit has finished drilling. Approximately 1-2 metres before the bit is pulled out of the hole, turn the air off. This will ensure that the bearings are blown clean, that you avoid duct blockage, jamming of the rollers & you don’t blow any of the collar back down the hole.
  • Check flushing air through all 3 cones.
  • If the bit is to stay in the hole while adding drill steel, blow the hole clean for 60 seconds prior to turning off the air.
  • Always rotate the bit when moving in or out of the hole.
    • Helps in cleaning the cuttings from the hole.
    • Keeps cuttings from entering the bearings around the back face of the cone.
  • Inspect the rock bit after each hole and record the condition of the rock bit at regular intervals.
  • Always use the highest possible air-pressure and flow rate in holes that contain a lot of water to avoid bearing problems.
  • When adding extra drill steel in wet holes, always make three or four cleaning passes to get a cleaner hole bottom.
  • Use the factory recommended weight and rotation speeds to accommodate the formations being drilled. Rotary speed should be decreased as down pressure is increased and down pressure decreased as rotary speed is increased.
  • Provide adequate air to the bit to ensure trouble free bearing performance and reduced abrasion wear on cones and shirttails. Air volume to clean the hole is referred to as bailing velocity (BV). Generally speaking, the higher the bailing velocity, the better the hole is cleaned and the higher the penetration rates and bit life.
    • An up-hole bailing velocity of 6000-7000 feet per minute (fpm) (30-36 m/s) is sufficient in light to medium materials (typically coal overburdens).
    • In more dense materials (hard rock mines, iron ore, etc.) or when encountering ground water, maintain an uphole bailing velocity of 7000-10000 fpm (36-50 m/s).
  • Some indications that the hole is not being properly cleaned are:
    • Increase in torque indication through higher hydraulic pressure
    • Increase in air pressure
    • Heavy wear and /or damage indications on shirttails
  • Monitor Pressures.
    • An increase in air pressure may indicate unwanted restrictions in the air system.
    • A decrease in air pressure may indicate leakage in the air system.
  • Store the bits away from dust.
    • Air Bearing storage: For extended storage, store air bearing bits in a sealed container with enough diesel to cover the bearings. This is useful during hole size changes or extended drill servicing.
    • Sealed Bearing storage: Clean and dry bits with air, then store in a sealed box or container. IMPORTANT: sealed bearing bits should NOT be soaked in diesel or other fluids or greases.
  • Accurate information is valuable knowledge. Always record metres drilled, time in the hole, rpm, weight on bit, psi, formation drilled and any unusual drilling conditions. (Water in the hole, broken formations, etc.)
  • After each bit is discarded it is necessary to make a comparative analysis of each bit type dulling and causes. Evaluating those findings can increase drilling efficiency while reducing drilling cost and will precisely determine what bit design features are required for the application.