FlexiROC T30 R 8 Drilling System
53 No: 3629357835.1.3629419915 en-US
2.
Raise and lower the rotation speed using button and respectively.
3.
Count the number of revolutions the drill string completes per minute (make a mark
on the drill rod) to measure rotation speed. Alternatively, use an electronic instrument.
Correct rotation speed must be set according to the type of drill bit and the properties
of the rock. Observe the following guidelines:
Size of drill bit, mm 76 89
Size of drill bit, inches 3 3 1/2
Rotation speed rpm 120 110
Table2: Basic setting for ordinary button drill bits
Type of drill bit
n X drill bits (cross-head bits) require a higher
speed than button drill bits (1020 rpm higher).
Rock properties
n Soft types of rock normally require a higher
speed, harder rock requires a lower rotation
speed.
Jerky rotation
n Jerky rotation speed during drilling (not rotat-
ing at even speed) could indicate that the ro-
tation speed is too low.
n In certain types of rock, ballistic drill bits can
cause jerky rotation.
Drill bit wear
n Diametric wear can be reduced if rotation
speed is lowered
Penetration rate
n High rotation speed can give a higher pene-
tration rate.
n Ballistic button drill bits normally give a higher
penetration rate.
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