Trouble Shooting

DTH BUTTON BIT TROUBLE SHOOTING

BIT FACE SELECTION

CONCAVE

  • Suitable for drilling in all formations.
  • Cone shaped depression in the face has centering effect for straighter holes.
  • Well suited for soft to medium formations.

FLAT

  • Face slots help eliminate bit plugging in softer zones.
  • More carbide to surface contact for better rock fracture.
  • Well suited for medium to hard formations.
                                                           CONVEX
  • Fast penetration rates.
  • Face design allows for increased body support for gage carbide.
  • Well suited for hard and abrasive formations.
1. Lower the bit to “bottom”. The bit will move into the work position and the hammer will begin to operate. Adjust the weight on bit to attain smooth operation and optimum performance from the hammer. The general rule of thumb for a starting weight on bit is as follows:500 pounds per inch of bit diameter
9 kg per mm of bit diameterIn a wet hole or unconsolidated material, it will be necessary to feed the hammer slowly to sufficiently clean the hole as the hammer is advanced. Care should be taken to limit the power developed by the hammer when drilling in these conditions. This is done by the operator controlling the feed.When the edge of a boulder is encountered and rotation becomes erratic or stalls raise the drill enough to clear the edge of the boulder and slowly feed until the edge is drilled off. Repeat the process until the rotation becomes smooth.When a solid formation is encountered, the rotation will stabilize and the hammer will sound strong and smooth. Adjust the rotation speed and weight on bit accordingly. Stay alert to the possibility that the solid formation may be a large boulder with loose material below. As soon as the hammer sound changes or the rotation torque fluctuates, lift the hammer and bit off bottom. Keep the rotation on and lower carefully to continue drilling.

It is good practice to monitor the hole flushing. It may be necessary to lift the hammer off bottom periodically to flush the hole until all the cuttings have been removed. Maintain rotation during this procedure.

Upon completion of the hole, lift the bit off bottom and flush the hole for several minutes to ensure no suspended material falls back on top of the hammer and drill bit. Maintain rotation during this procedure. It may be necessary, in difficult drilling conditions, to continue flushing the hole and rotating until the bit is at ground level.

2 – SharpeningCarbide inserts should be sharpened when the buttons exhibit flats equal to 1/3 the diameter of the insert.

Original Carbide Diameter

Sharpen When Carbide Reaches

1/2″ (12.7 mm) 5/32″ (4.0 mm)
9/16″ (14.3 mm) 3/16″ (4.8 mm)
5/8″ (15.9 mm) 7/32″ (5.6 mm)
3/4″ (19.1 mm) 1/4″ (6.4 mm)

When the wear flat reaches 1/2 the diameter of the insert they are subjected to severe radial forces.
Although carbide inserts can withstand extreme longitudinal loading, they are easily fractured when subjected to severe radial loading. In addition, when the carbide inserts are severely worn drilling speed is reduced dramatically.

3 – Drilling After Carbide Insert FailureAfter the bit has experienced carbide insert failures, further drilling allows the steel matrix to be eroded quickly. It is not particularly evident when only one insert is broken. However, when more than one insert in succession are broken, the steel matrix erodes rapidly.Once the matrix of the bit body is worn away, that area of the bit can no longer be repaired. If possible, carbide insert failure should be reported immediately and the bit scheduled for repair. Continued usage after carbide failure may damage the bit to a point where it needs to be replaced.