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

Extension Springs

2

String

Roll

Instructions

1. Attach String to Thumb Joint 3

Part Name
Quantity

String

~ 1.5 ft

Thumb Joint 1

1

  1. Put both ends of the string in the holes.

  1. Pull them through

  1. Taking both ends of the string tie a slip knot using the following steps.

  1. Tighten the slipknot and trim the blue end.

  1. Push the knot into the joint. This may require tweezers.

  1. 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

  1. Pull string through hole.

  1. Tie slip knot (same as previous step).

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  1. Tighten the knot and feed it through the joint.

  1. Pull the string through the joint.

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3. Attach String to Thumb Joint 1

Part Name
Quantity

String

~ 1.5 ft

Thumb Joint 1

1

  1. Bend the end of the string slightly.

  1. Feed it through the internal hole and pull through.

  1. Tie a slipknot and trim the end.

  1. Tighten the knot.

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/ they are not moving, you may have to drill/file the outer holes so that the joint moves freely like in the video.

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 Torsion Spring

Part Name
Quantity

Torsion Spring

1

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