3. Read and translate the text

Rock bits with tungsten carbide inserts (compacts) instead of milled teeth on the cutting structure were originally developed for drilling hard formations whose abrasiveness would wear out the conventional milled-tooth bits. In soft formations, insert bits were unsatis­factory because the inserts could not be made long enough to achieve the scraping-gouging ef­fect. The shorter inserts that had to be used allowed a greater volume of mud to flow across the cones, and since the cones were relatively soft in order to house the inserts, cone erosion became a problem.

Today's insert bits are extremely durable and are able to drill in different formations. As usual, the question of when to use an insert bit is primarily an economic one. They can cost two or three times as much as milled-tooth bits, but they can provide more consistent rates of pene­tration (especially in abrasive streaks) and cut down on the number of trips because they generally last longer. The shape and placement of the inserts on the cutting structure vary in much the same way as do the teeth on milled-tooth bits. Different combina­tions of features are needed as formations change from soft to hard. In soft shales, lime­stones, clay, red beds, and sandstone, large-diameter projectile-shaped inserts set in offset cones produce the scraping-gouging action necessary to drill in soft strata. In forma­tions that are similar except for the presence of abrasive streaks such as hard sandstone, shorter chisel-crest bits with less cone off­set combine scraping action with crushing action to maintain constant penetration through the formation changes. Shorter, blunter inserts are characteristic of bits used in hard limestones, dolomite, chert, and hard shales. The maximum number of tungsten car­bide compacts in the outermost area helps prevent wear. Hardfacing on the exterior part of the cone housing also ensures longer time in the hole.

4. Give the adequate Russian variants for the following word combinations:

Rock bits with tungsten carbide inserts; to wear out the conventional milled-tooth bits; to achieve the scraping-gouging ef­fect; to cost two or three times as much as milled-tooth bits; to provide more consistent rates of pene­tration; to cut down on the number of trips; the shape and placement of the inserts; the presence of abrasive streaks; chisel-crest compacts with less cone off­set; to maintain constant penetration; hardfacing on the exterior part of the cone housing.

5. Agree or disagree with the following statements:

1. Rock bits with tungsten carbide inserts were originally developed for drilling soft formations.

2. Today's insert bits are extremely durable and are able to drill in different formations.

3. Insert bits can provide more consistent rates of pene­tration and cut down on the number of trips.

4. Insert bits are much cheaper than milled-tooth bits.

5. The shape and placement of the inserts on the cutting structure vary as formations change from soft to hard.

6. Large-diameter projectile-shaped inserts set in offset cones produce the scraping-gouging action necessary to drill in soft strata.

7. Shorter chisel-crest bits with less cone off­set combine scraping action with crushing action to maintain constant penetration through the formations containing abrasive streaks.

8. Shorter, blunter inserts are characteristic of bits used in soft shales, lime­stones and red beds.

9. The maximum number of tungsten car­bide compacts and hardfacing help to prevent wear and ensure longer time in the hole.