The early Cy/Cool Girls come with shiny vinyl hands that have a single axis hinge for the wrist (v1 hands, bottom of the picture).
Later releases come with hands with an added axial hinge in the base of the hand, allowing for more poses (v1.5 hands, center of the picture).
Unfortunately some styles of hands were only made as v1 hands, e.g. the only bare v1.5 hands that I know of came with the 'Best of CG' rerelease of Ruby and with Kisaragi Honey so these are pretty rare.
Note that CG v2 bodies and several clones come with a variation of the v1.5 hands, these have 4 small notches in the locking groove (v2 hands, top of the picture, notches indicated by violet arrows).
As far as I can tell these notches serve no useful purpose but they do limit the wrist rotation to 90 degree steps, so I usually cut the notches down to achieve a continuous groove similar to that of a v1.5 hand.
Here's how to modify a v1 hand to accept a v1.5 wrist.
| Please note that this is a destructive procedure, if something goes wrong, the v1 hand can not be restored and is likely to be unusable. |
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Tools and materials needed:
 | First warm up the v1.5 donor hand until it is lukewarm, then pop the hand off its wrist. Save the donor hand, you can always put it back on a v1.5 wrist later. |
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Cut the lugs for the wrist off of the v1 hand as shown in the pictures.For a gloved hand I use a straight cut, for a bare hand I prefer to make a slightly V-shaped cut so the remains of the lugs wrap around the ball joint of the v1.5 wrist. Clean up any sharp edges. Keep the parts of the v1 wrist as spares. The diagram on the right shows a cross section of the hand near the wrist. |
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Use the large ball shaped cutter head to shape a slightly hollow recess in the base of the hand for the v1.5 ball joint. |
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Drill a 2.5mm diameter hole in the center of the recess in the base of the hand, drill 4mm (0.157in) deep.I use a piece of masking tape around the drill at 4mm from the tip as a depth gauge. Note that 2.5mm diameter is actually a bit tight for the v1.5 wrist pin but this is to make sure the hand fits firmly and will hold any pose. For this same reason I use a pin vise instead of the motor tool to drill the hole: with a motor tool the hole often ends up slightly wider than the drill size. |
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Use the small ball shaped cutter head to widen the inside of the hole.Create a mushroom shape by twirling the cutter around inside the hole. Be sure to leave a 1.0mm (0.04in) deep ridge at the open end of the hole at 2.5mm diameter. |
 | Clean up any burrs and touch up any paint if necessary. Warm up the hand, then insert the mushroom shaped pin of the v1.5 wrist into the newly drilled hole in the hand. That's all ! |
