Starting a Diamond Drill Bit
It is recommended that circulation be started prior to reaching bottom and
that extreme care be used to find bottom. The bit should be rotated slowly
to bottom, or if possible establish bottom with zero rotation. Then circulate
with full volume and rotate slowly at a point about one foot or less off
bottom for a period of at least five minutes to clean the bottom of the hole.
After circulating, use extreme care to find bottom. Within the minimum bit
weight and full fluid volume, drill enough hole to form a new bottom hole
contour. This is important since a diamond bit does not get proper cleaning
and cooling action until the bottom of the hole exactly fits the bit profile.
Under some conditions, procedures may dictate touching bottom with full
pump force but no rotation in order to try to crush any irregular large
foreign particles on the bottom of the hole, with minimum of bit damage.
This procedure, when appropriate, should be used several times before
rotating the drill string.
It is recommended that circulation be started prior to reaching bottom and
that extreme care be used to find bottom. The bit should be rotated slowly
to bottom, or if possible establish bottom with zero rotation. Then circulate
with full volume and rotate slowly at a point about one foot or less off
bottom for a period of at least five minutes to clean the bottom of the hole.
After circulating, use extreme care to find bottom. Within the minimum bit
weight and full fluid volume, drill enough hole to form a new bottom hole
contour. This is important since a diamond bit does not get proper cleaning
and cooling action until the bottom of the hole exactly fits the bit profile.
Under some conditions, procedures may dictate touching bottom with full
pump force but no rotation in order to try to crush any irregular large
foreign particles on the bottom of the hole, with minimum of bit damage.
This procedure, when appropriate, should be used several times before
rotating the drill string.
