> For the complete documentation index, see [llms.txt](https://ruka.gitbook.io/instructions/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ruka.gitbook.io/instructions/hardware/thumb-assembly.md).

# Thumb Assembly

## **Materials**

#### **Tools**

* Tweezers
* Razor Blade or Scissors
* 1.5 mm Allen Key

#### **3D Printed Parts**

<table><thead><tr><th width="252">Part Name</th><th width="144" align="center">Total Quantity</th></tr></thead><tbody><tr><td>Thumb Joint 1  </td><td align="center">1</td></tr><tr><td>Thumb Joint 2</td><td align="center">1</td></tr><tr><td>Thumb Joint 3</td><td align="center">1</td></tr></tbody></table>

#### **Hardware (Total)**

<table><thead><tr><th width="252">Part Name</th><th width="144" align="center">Total Quantity</th></tr></thead><tbody><tr><td>Dowel</td><td align="center">2</td></tr><tr><td>M2 x 4 mm Screws</td><td align="center">4</td></tr><tr><td>M3 x 12 mm Screw</td><td align="center">1</td></tr><tr><td>Extension Springs</td><td align="center">2</td></tr><tr><td>String</td><td align="center">Roll</td></tr></tbody></table>

***

## Instructions

### 1. Attach String to Thumb Joint 3

<table><thead><tr><th width="270">Part Name</th><th width="100">Quantity</th></tr></thead><tbody><tr><td>String</td><td>~ 1.5 ft</td></tr><tr><td>Thumb Joint 1</td><td>1</td></tr></tbody></table>

{% embed url="<https://drive.google.com/file/d/1FjmM2tOJpZo1fPmzkJOtuLqWfnJ2LKRB/view?quality=hd&usp=sharing>" %}

<table data-header-hidden data-full-width="false"><thead><tr><th></th><th></th><th></th></tr></thead><tbody><tr><td><ol><li><strong>Put both ends of the string in the holes.</strong></li></ol></td><td><ol start="2"><li><strong>Pull them through</strong> </li></ol></td><td><ol start="3"><li><strong>Taking both ends of the string tie a slip knot using the following steps.</strong></li></ol></td></tr><tr><td><img src="/files/0IHSFbw0evQXED8RhgM3" alt=""></td><td><img src="/files/xXhR4pJvpgX427s8F4gi" alt=""></td><td><img src="/files/UPav7WEJ1Y8UsYijanDu" alt=""></td></tr><tr><td><ol start="4"><li><strong>Tighten the slipknot and trim the blue end.</strong></li></ol></td><td><ol start="5"><li><strong>Push the knot into the joint. This may require tweezers.</strong></li></ol></td><td><ol start="6"><li><strong>Feed the string to the other side of the pulley.</strong></li></ol></td></tr><tr><td><img src="/files/lj8zvGTlYttiFR7RD0qs" alt=""></td><td><img src="/files/iiUaUQiWUhC1dkriB6ui" alt=""></td><td><img src="/files/70iu0N0xosxR0DBxaDw8" alt=""></td></tr></tbody></table>

### 2. Attach String to Thumb Joint 2

<table><thead><tr><th width="270">Part Name</th><th width="100">Quantity</th></tr></thead><tbody><tr><td>String</td><td>~ 1.5 ft</td></tr><tr><td>Thumb Joint 2</td><td>1</td></tr></tbody></table>

{% embed url="<https://drive.google.com/file/d/19NlGjLIsoCUVf1Xmq8hWuLdk1XlBgZvP/view?quality=hd&usp=sharing>" %}

| <ol><li><strong>Pull string through hole.</strong></li></ol>                   | <ol start="2"><li><strong>Tie slip knot (same as previous step).</strong></li></ol> |
| ------------------------------------------------------------------------------ | ----------------------------------------------------------------------------------- |
| ![](/files/1aMgCanWpLqNIMU36U7P)                                               | ![](/files/KPxTexhSi38oOGuVZ9Iu)                                                    |
| <ol start="3"><li><strong>Tighten the knot and trim the end</strong></li></ol> | <ol start="4"><li><strong>Pull the string through the joint.</strong></li></ol>     |
| ![](/files/f1oZFphzePKub0SeAf1r)                                               | ![](/files/FQwZwuF9nQnkXAm5zoAK)                                                    |

### 3. Attach String to Thumb Joint 1

<table><thead><tr><th width="270">Part Name</th><th width="100">Quantity</th></tr></thead><tbody><tr><td>String</td><td>~ 1.5 ft</td></tr><tr><td>Thumb Joint 1</td><td>1</td></tr><tr><td>M3 x 12 mm Screw</td><td>1</td></tr></tbody></table>

<table data-header-hidden data-full-width="true"><thead><tr><th></th><th></th></tr></thead><tbody><tr><td><ol><li><strong>Tie a slip knot</strong></li></ol></td><td><ol start="2"><li><strong>Put the loop into the thumb</strong></li></ol></td></tr><tr><td><img src="/files/1bSuI9s2Wxr2tH43Q4X7" alt=""></td><td><img src="/files/YzrOzcF8limLz86iCsl7" alt=""></td></tr><tr><td><ol start="3"><li><strong>Screw the bolt in through the string loop</strong></li></ol></td><td><ol start="3"><li><strong>Tighten the knot and trim the tail</strong></li></ol></td></tr><tr><td><img src="/files/1q8I6qlrT121178n5dDs" alt=""></td><td><img src="/files/Kuugzq5DEH0aLeB3gMVd" alt=""></td></tr></tbody></table>

### 4. Connect Joints with Dowels

<table><thead><tr><th width="270">Part Name</th><th width="100" data-type="number">Quantity</th></tr></thead><tbody><tr><td>Dowels</td><td>2</td></tr><tr><td>Thumb Joint 1</td><td>1</td></tr><tr><td>Thumb Joint 2</td><td>1</td></tr><tr><td>Thumb Joint 3</td><td>1</td></tr></tbody></table>

{% embed url="<https://drive.google.com/file/d/1IV7uZMeOARnHyT09AiVlHXpuGXc9hQQ6/view?quality=hd&usp=sharing>" %}

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.

<figure><img src="/files/9kHEs7JV9jGP3ZiuonbZ" alt=""><figcaption></figcaption></figure>

***

### 5. Attach Extension Springs

<table><thead><tr><th width="270">Part Name</th><th width="100" data-type="number">Quantity</th></tr></thead><tbody><tr><td>Extension Springs</td><td>2</td></tr><tr><td>M2 x 4 mm Screws</td><td>4</td></tr><tr><td>Thumb Joint 1</td><td>1</td></tr><tr><td>Thumb Joint 2</td><td>1</td></tr><tr><td>Thumb Joint 3</td><td>1</td></tr></tbody></table>

{% embed url="<https://drive.google.com/file/d/151125Jx-dRbDunQl4pZgJJJ3Xm-3L6vI/view?quality=hd&usp=sharing>" %}

<table data-header-hidden data-full-width="false"><thead><tr><th width="289" align="center"></th><th></th><th data-hidden data-type="files"></th></tr></thead><tbody><tr><td align="center"><strong>Thumb Joint 2 + 3</strong></td><td><strong>Thumb Joint 1 + 2</strong></td><td></td></tr><tr><td align="center"><strong>x 2</strong> - M2 x 4 x 3.5</td><td><strong>x 2</strong> - M2 x 4 x 3.5</td><td></td></tr><tr><td align="center"><strong>x 1</strong> - Extension Spring</td><td><strong>x 1</strong> - Extension Spring</td><td></td></tr><tr><td align="center"><img src="/files/OysiEGLiWLtq6cSCT9si" alt=""></td><td><img src="/files/RFC4RFk9HQGi2QjB4yTK" alt=""></td><td><a href="/files/zN2enCDtgxBZjIjPhhbr">/files/zN2enCDtgxBZjIjPhhbr</a></td></tr></tbody></table>

### 6. Check Actuation and Add Torsion Spring

<table><thead><tr><th width="270">Part Name</th><th width="100" data-type="number">Quantity</th></tr></thead><tbody><tr><td>Torsion Spring</td><td>1</td></tr></tbody></table>

{% embed url="<https://drive.google.com/file/d/17gWnx82Yxi9-bP2waKvg3lOsBXdK0FKJ/view?quality=hd&usp=sharing>" %}


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