> 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/finger-assembly.md).

# Finger Assembly

{% hint style="warning" %}
**These are instructions for one finger, so repeat them 4x to build the index, middle, ring, and pinky fingers**
{% endhint %}

{% hint style="info" %}
Note that Pinky and Thumb parts are denoted by a P and T printed on the parts. The index, middle, and ring fingers are identical and have no labels.
{% endhint %}

***

## **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>Finger Joint 1  </td><td align="center">3</td></tr><tr><td>Finger Joint 2</td><td align="center">3</td></tr><tr><td>Finger Joint 3</td><td align="center">3</td></tr><tr><td>Pinky Joint 1</td><td align="center">1</td></tr><tr><td>Pinky Joint 2</td><td align="center">1</td></tr><tr><td>Pinky 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">8</td></tr><tr><td>M2 x 4 mm Screws</td><td align="center">16</td></tr><tr><td>Extension Springs</td><td align="center">8</td></tr><tr><td>String</td><td align="center">Roll</td></tr></tbody></table>

***

## Instructions

Quantities are per finger per step.

### 1. Attach String to 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>Finger Joint 3 / Pinky Joint 3</td><td>1</td></tr></tbody></table>

{% embed url="<https://drive.google.com/file/d/1i-olQmIt85LAa1q8EznjtHhKbQGOc0WV/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 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>Finger Joint 1 / Pinky Joint 1</td><td>1</td></tr></tbody></table>

{% embed url="<https://drive.google.com/file/d/1QtN6DZb8jowJS-jLchCSAsiMHIbXqqxs/view?quality=hd&usp=sharing>" %}

<table data-header-hidden><thead><tr><th width="403"></th><th></th></tr></thead><tbody><tr><td><ol><li><strong>Pull string through hole.</strong></li></ol></td><td><ol start="2"><li><strong>Tie slip knot (same as previous step).</strong></li></ol></td></tr><tr><td><img src="/files/1hylOyTbXxcEab1OreDK" alt=""></td><td><img src="/files/XMDpysNEaEe4b1Fpo0r5" alt=""></td></tr><tr><td><ol start="3"><li><strong>Tighten the knot and feed it through the joint.</strong></li></ol></td><td><ol start="4"><li><strong>Pull the string through the joint.</strong></li></ol></td></tr><tr><td><img src="/files/WjKKkezuMe75PjrZ0mKH" alt=""></td><td><img src="/files/I7iPntpSduzTmgkMoyqx" alt=""></td></tr></tbody></table>

### 3. Connect Joints with Dowels

It is easiest to route the string before putting together the dowels.&#x20;

It can also be done after, but may require the help of tweezers.&#x20;

<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>Finger Joint 1 / Pinky Joint 1</td><td>1</td></tr><tr><td>Finger Joint 2 / Pinky Joint 2</td><td>1</td></tr><tr><td>Finger Joint 3 / Pinky Joint 3</td><td>1</td></tr></tbody></table>

{% embed url="<https://drive.google.com/file/d/1ztUL2zUN7m0KQJIjGjgdTF4rNnV08t0J/view?quality=1080p&usp=sharing>" %}

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.

<div><figure><img src="/files/nqdE6K87U514ZePav36f" alt="" width="474"><figcaption></figcaption></figure> <figure><img src="/files/xv83zD0bkwSZ8bAkNMdu" alt="" width="375"><figcaption></figcaption></figure></div>

***

### 4. 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>Finger Joint 1 / Pinky Joint 1</td><td>1</td></tr><tr><td>Finger Joint 2 / Pinky Joint 2</td><td>1</td></tr><tr><td>Finger Joint 3 / Pinky Joint 3</td><td>1</td></tr></tbody></table>

{% embed url="<https://drive.google.com/file/d/1GalC1rVzTSCMbO45sPgFJa_F9k7gemwd/view?quality=hd&usp=sharing>" %}

<figure><img src="/files/fabNwtDsF1N12iSDRYQb" alt="" width="312"><figcaption></figcaption></figure>

***

**You should have four assembled fingers at this point.**


---

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