Hitachi Koki GP 2 - GP2 1" Die Grinder (4.7 AMP) Safety Instructions And Instruction Manual page 14

English
Wheels can be simply attached and detached by using two wrenches. (Fig. 3)
Tighten
NOTE: Do not tighten the collet chuck by inserting a shaft thinner than the regular
shaft diameter (1/4''(6.35mm)) in the chuck or in an empty condition. This
practice will damage the collet chuck.
When installing a wheel with shaft, tighten the collet chuck after applying a
small quantity of spindle oil (or sewing machine oil) to the tapered portion
indicated in Fig. 2.
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Collet chuck
Fig. 2
Spindle
Collet chuck
Fig. 3
Tapered portion