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10. Ряди зубців на внутрішній частині кожної шарошки
взаємно прилягають на сусідніх шарошках.

Exercise 3. Translate following words and word-
combinations
Drill string, bit, downhole tools, forerunner, fishtail, cutting
blade, bit shank, junk, forge, anvil, hardfacing, cone bit, dull,
dress, ream, bearing, cutter type bit, journal bearing, load, prime
mover.

Exercise 4. Fill in the gaps
The 1).... at the bottom of the drill string is the indispensable
tool. Without it allother items of the conventional 2).... rig are
useless. Other rig items merely supportbit functions. Bits of many
designs have been used in rotary drilling but all require 3).... plus
rotary motion in order to make hole.The 4).... of all rotary drilling
bits isthe 5)...., so called because the cutting blade resembles the
tail of fish.
After a period of use in drilling, the blade became 6)....and
had to besharpened. This usually was done at the 7)…using forge,
anvil, and man power athand. Fishtail bits were first referred to as
8)… . In the late 'teens Hughes brought outthe famous simplex
two-cone bit with long9)... body having side reamers andlubricated
10)....The jet principle were first applied to as drag bits and
provedeffective. Higher cost of jet bits was justified in deep
drilling because 11)... couldbe done with less drilling fluid being
circulated and less friction loss in 12)....The most recent
improvement in rock bits is 13)..., particularly lubricatedjournal-
type bearings. Rows of teeth on the inner portion of each cone
14)... thegrooves on adjacent cones. This provides positive 15)...
action and permits the bestuse of available space for both teeth and
bearings.

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