Thumb Assembly

Materials

Tools

• Tweezers

• Razor Blade or Scissors

• 1.5 mm Allen Key

3D Printed Parts

Part Name	Total Quantity
Thumb Joint 1	1
Thumb Joint 2	1
Thumb Joint 3	1

Hardware (Total)

Part Name	Total Quantity
Dowel	2
M2 x 4 mm Screws	4
M3 x 12 mm Screw	1
Extension Springs	2
String	Roll

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Instructions

1. Attach String to Thumb Joint 3

Part Name	Quantity
String	~ 1.5 ft
Thumb Joint 1	1

Put both ends of the string in the holes.	Pull them through	Taking both ends of the string tie a slip knot using the following steps.
Tighten the slipknot and trim the blue end.	Push the knot into the joint. This may require tweezers.	Feed the string to the other side of the pulley.

2. Attach String to Thumb Joint 2

Part Name	Quantity
String	~ 1.5 ft
Thumb Joint 2	1

Pull string through hole.	Tie slip knot (same as previous step).
Tighten the knot and trim the end	Pull the string through the joint.

3. Attach String to Thumb Joint 1

Part Name	Quantity
String	~ 1.5 ft
Thumb Joint 1	1
M3 x 12 mm Screw	1

Tie a slip knot	Put the loop into the thumb
Screw the bolt in through the string loop	Tighten the knot and trim the tail

4. Connect Joints with Dowels

Part Name	Quantity
Dowels	2
Thumb Joint 1	1
Thumb Joint 2	1
Thumb Joint 3	1

The joints should be able to move freely. If there is friction, you may have to drill/file the outer holes so that the joint moves freely, like in the video.

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5. Attach Extension Springs

Part Name	Quantity
Extension Springs	2
M2 x 4 mm Screws	4
Thumb Joint 1	1
Thumb Joint 2	1
Thumb Joint 3	1

Thumb Joint 2 + 3	Thumb Joint 1 + 2
x 2 - M2 x 4 x 3.5	x 2 - M2 x 4 x 3.5
x 1 - Extension Spring	x 1 - Extension Spring

6. Check Actuation and Add Torsion Spring

Part Name	Quantity
Torsion Spring	1