Ditch Witch OnGrade - Manual (Page 37)

Conduct OnGrade Bore - 36
OnGrade Operator’s Manual
Correct Depth
CMW
Drill-Thru
Drill-thru mode on the tracker provides left/right
guidance information as well as pitch information.
Depth information provided when using drill-thru
mode can be ignored when conducting an
OnGrade bore.
1. Stretch a string on the ground surface along
the bore path (2).
2. Place tracker ahead of the front of the drill
head between the drilling unit (1) and laser (5)
with the center line of the tube holding the outer pods directly over the string and the left pod (3) toward
the drilling unit.
3. Use left/right information to steer drill head and monitor pitch information closely.
The tracker must remain in front of the drill head and turned sideways with the left pod toward the drilling
unit. The center line of the tube holding the outer pods should be directly over the desired line of the bore.
Correct Depth
Correcting depth gradually is critical to the success of a grade bore.
Downhill or Downgrade Bore
If the measured depth from the laser plane to the beacon ever starts to become deeper than the target
depth, the driller should drill at a pitch slightly flatter than the the target grade until the grade of the bore
naturally catches up with the fall of the target grade.
Uphill or Upgrade Bore
If the measured depth from the laser plane to the beacon ever starts to become shallower than the target
depth, the driller should drill at a pitch slightly flatter than the the target grade until the grade of the bore
naturally catches up with the rise of the target grade.
IMPORTANT: See tracker manual for additional
drill-thru mode instructions.
IMPORTANT: Do not drill at a positive pitch to correct depth. This will create a dip in the bore path.
IMPORTANT: Do not drill at a negative pitch to correct depth. This will create a hump in the bore path.
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