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IMPREGNATED CORE BITS & REAMERS
The broad objective of an Impregnated Diamond Bit is to produce a bit where the Matrix, under given conditions, erodes at a rate, so that, as active diamonds
become blunt, they will be released and fresh, sharp diamonds will be exposed
to come into contact with the rock being drilled.
The matrix is a critical factor in impregnated bit manufacture, as it must have the
capacity to retain the synthetic diamonds for as long as they continue to cut but
to then wear at a rate that will allow non-performing diamonds to ‘strip’ out
and allow new sharp diamonds to be exposed.
The matrix must be strong enough to resist "pull out" of diamonds, but must not
be so strong as to resist the strip out of spent diamonds.
Diamond concentration is a further important consideration in an impregnated
core bit as it is believed that an increase in concentration reduces the ‘strip’
rate of the matrix and increases the load required for "self-sharpening"
Two extremes of matrix, diamond size and diamond concentration are possible.
At one extreme, the matrix is far too "hard" and worn diamonds are not
released. At the other extreme, the matrix releases diamonds prematurely,
while they still have some useful life left.
In the former case, the bit becomes glazed and excessive loads are required
to continue drilling, or the penetration stops altogether, whilst in the latter
case, the bit wears far too rapidly and bit costs increase significantly.
A final consideration in the manufacture of bits, be they surface set or
impregnated, is the water ways. As the matrix to rock clearance is much
less with impregnated bits than with surface set bits, the waterways assume
a greater degree of importance.
A relationship has been established between the operating efficiency of a bit
and the coolant flow, so that an adequate coolant flow is of prime importance.
Asahi Australia manufactures two types of impregnated bits, namely
ASAHI REGULAR SERIES for coarse grained abrasive or fractured rocks
and ASAHI TA SERIES for non abrasive fine grained rocks. The selection
of the optimum bit for the anticipated ground conditions requires careful consideration.
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