Summary

The gears make the wrist move back and forth.
The holes in the palm are for zip-ties, and it simulates the collapsing motion of the palm.
You will need both .dxf files.

Instructions

(1) Let's start with the hand_no_wrist_or_arm.dxf file. The palm is split into two parts (1 part for the four fingers, and 1 part for the thumb and wrist connection).
(1.a) Utilize one 1-slot/1-hole pieces in each of the finger slots, and two of them for the thumb slot (attach using wood glue or equivalent)
(1.b) Utilize two 2-hole pieces for the next finger-join on each of the fingers (one on both sides of the hole resulting from the pieces from 1.a), and just one for the thumb (attach using nuts and bolts or equivalent)
(1.c) Utilize one 2-hole pieces for the next finger-join on each of the fingers (one in between the pieces resulting from 1.b) (attach using nuts and bolts or equivalent)
(1.d) Utilize both 1-slot/2-hole pieces for the wrist slots (attach using wood glue or equivalent)

(2) Let's move on to wrist_and_arm.dxf
(2.a) In my build, I used dowel segments to provide the rod around which the gears could rotate. If you use the same, utilize the circular pieces and caps for either end of the rod. For now, attach caps only to one end of each of the 7 rods you will need. (utilize wood glue or equivalent)
(2.b) slide all seven rod/1-cap's into one of the frames.
(2.c) put the big-gear with two small holes onto the rod on the smaller end of the frame (this will attach to your wrist), and then fill in with an alternating big-gear/small-gear pattern
(2.d) place the second frame over the gears (should make a frame-gears-frame sandwich
(2.e) at this point some length of rod should be poking out from the frame-gears-frame sandwich, so attach caps to each of these
(2.f) place the big-gear with two holes in between the wrist pieces from your hand assembly, and connect using nuts and bolts or equivalent

Happy fabricating!

Simple Mechanical Arm