NPK GH7 - Maximum Tool to Tool Bushing Clearance

NPK
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TOOLS
MAXIMUM TOOL TO TOOL BUSHING CLEARANCE
Replace the tool bushing (G), and/or tool (HH), when the tool to bushing gap reaches
the maximum clearance. To determine whether the bushing or tool requires
replacement, follow the instructions and charts shown below:
Step 1
Measure the tool to bushing gap (d15) with the hammer horizontal, as illustrated below.
If the clearance is at or greater than the charted maximum clearance, consult the NPK
Hydraulic Hammer Service Manual to determine which component requires
replacement.
MODEL
MAXIMUM CLEARANCE
inch (mm)
GH7 3/8 (10)
GH9 3/8 (10)
GH10 3/8 (10)
GH12 1/2 (13)
GH15 1/2 (13)
GH18 1/2 (13)
GH23 5/8 (16)
GH30 5/8 (16)
GH40 5/8 (16)
GH50 5/8 (16)
Step 2
Remove the tool from the tool holder. Measure the diameter (d16) of the bearing
surface of the tool, which is located on each side of the retaining pin groove. The
minimum tool diameter is compared to a new tool bushing only. If the tool is at, or
below the charted value, the tool must be replaced.
MODEL
NEW TOOL DIAMETER
(d16) inch (mm)
MINIMUM TOOL DIAMETER
inch (mm)
GH7 4.6 (116) 4.2 (106)
GH9 5.0 (126) 4.6 (116)
GH10 5.4 (136) 5.0 (126)
GH12 5.7 (146) 5.2 (132)
GH15 6.1 (156) 5.6 (142)
GH18 6.5 (165) 6.0 (152)
GH23 6.9 (174) 6.2 (158)
GH30 7.2 (184) 6.6 (168)
GH40 8.0 (204) 7.4 (188)
GH50 8.4 (214) 7.8 (198)