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HandChestnut Robotics (formerly TetherIA)2025US

Aero Hand Open

Open-source tendon-driven five-finger hand with 7 actuated DOF (16 joints), fully 3D printed, weighing 389 g, with a Python SDK and ROS2 support.

activeKitL2 Sim-verifiedbuildable

Difficulty index

5.5/13
5.5
Index breakdown
Classhand+3
Cost$324 BOM+0.5
DOF7 DOF+0.7
Parts194 parts+1.3
How the index works

Specimen photographs

6 items
  • Aero Hand Open studio render, three-quarter front view
    Studio render of the published MJCF, keyframe pose from the model. Geometry only; colours are the model's own materials.Rendered by Hyperspawn from mujoco_menagerie/tetheria_aero_hand_open (Apache-2.0) · Hyperspawn render · source
  • Aero Hand Open studio render, side view
    Side view of the same MJCF render, keyframe pose from the model.Rendered by Hyperspawn from mujoco_menagerie/tetheria_aero_hand_open (Apache-2.0) · Hyperspawn render · source
  • 4 s turntable of the MJCF studio render.Rendered by Hyperspawn from mujoco_menagerie/tetheria_aero_hand_open (Apache-2.0) · Hyperspawn render · source
  • Aero Hand Open in three poses, tendon-driven fingers
    Banner from the aero-hand-open repo.Chestnut Robotics (aero-hand-open) · CC-BY-NC-SA-4.0 · source
  • Introducing Aero Hand Open | TetherIA’s First Open-Source Robotic HandChestnutRobotics · official video, embedded · source
  • Aero Hand Open Lifts a 5-Gallon Water Jug | Open-Source Robotic Hand Strength Test #roboticsChestnutRobotics · official video, embedded · source

Spec card

5/13 known
Degrees of freedom
7
Mass
0.389 kg
Price
$314 · Complete kit $314
BOM total
$324 · 20/24 lines priced
Part count
194

Not in the registry: height, payload, speed, runtime, battery, actuators, compute, sensors. Left blank rather than guessed.

What you learn building it

  • +Tendon and linkage transmissions
  • +Controlling many coupled joints
  • +Tactile and proprioceptive sensing
  • +Cable routing in tight spaces
  • +FDM 3D printing: 38 parts
  • +Tools used: FDM printer, bed >= 200 x 200 mm, Flush cutters, Files / sandpaper, Jewelry hand drill, 1.0 mm, 2.0 mm and 2.1 mm drill bits, Scissors / razor blade, Tape measure, Needle-nose pliers +22
  • +23 assembly steps across 10 subassemblies
  • +Flashing firmware for Seeed XIAO ESP32S3 (hand controller, 16-byte binary serial protocol, default 921600 baud), Feetech HLS3606M bus servos, IDs 0-6
  • +Testing in simulation (URDF/MJCF) before touching hardware

Openness

90/100
  • publicCAD
  • publicBOM
  • publicFirmware
  • publicSim model
  • publicSoftware
  • not publicPolicies

Score 90/100 computed from what is public: CAD 25, BOM 20, sim 20, firmware 15, software 10, policies 10. Hardware license: CC-BY-NC-SA-4.0. Software license: Apache-2.0.

Repos & models

URDF ↗MJCF ↗MuJoCo Menagerie ↗
DocsBuy

Build it

Has an ORP build package.
BOM total
$324
Lines priced
20/24
Parts
194
Steps
23
Version
0.1.0

4 lines have no price yet, so the real total is higher.

Largest BOM lines

Largest bill of materials lines
PartQtyUnit
Feetech HLS3606M 6 V smart servo (with mount plate, M2.3x5 spline screw, M2x4 plate screws and connection cable)HLS3606M7$29.83
Finger distal/medial and thumb proximal/distal return spring (PIP), music wirePE020-140-33500-MW-0840-MH-N-IN5$5.27
SparkFun snappable protoboard (optional control board / busbar)1$13.5
Finger proximal/MCP return spring (MP), music wireM-35CS4$3.27
2x5x2.5 mm miniature bearing (MR52ZZ)MR52ZZ23$0.522
M2 x 6 flanged Torx self-tapping screw96817A40625$0.403
Seeed Studio XIAO ESP32S3 (hand controller)XIAO ESP32S31$7.99
Braided Vectran (or Kevlar) cord, spool: 11 tendons of 300 mm (4 finger pull incl. pinky, 4 finger coupling, thumb CMC flex, thumb pull, thumb coupling)1$6.29

Fabrication

  • FDM 3D printing38
Firmware repo
  • BOM total is $316.48 per hand in USD as stated in BOM.csv (printed parts and silicone are costed by volume, so real filament and silicone purchases cost more). The README quotes a $314 kit.
  • The 6 V servo power supply and XT30 connector appear in the assembly guide but not in BOM.csv; no model or vendor is given. Size it for about 10 A peak per the firmware README.
  • Design files (CAD, STL, BOM, docs) are CC BY-NC-SA 4.0, non-commercial; commercial manufacturing needs a licence from Chestnut Robotics. Firmware and SDK are Apache-2.0.
  • Several BOM links were long search URLs; tracking parameters are stripped here. MISUMI undersized-pin links point at a series page where you select the size.
  • Cable lengths per servo come from a table in the guide that is partly hard to read; only servo 1 (90 mm) and servos 3-5 (140 mm) are stated unambiguously. Check the guide page 10 for servos 2 and 6.
  • The BOM row labels and the guide's part numbers differ (e.g. undersized 2x10 is P/N 37 in the BOM and 32 in the guide).
  • The RL deployment README calls the GUI `aero-hand-gui`; the SDK installs `aero-open-gui`. The README also says `--select-packages`; colcon's flag is `--packages-select`.
  • The BOM lists one undersized 2x20 pin that the guide never calls out by name; this package puts it with the thumb CMC pins. Check the Onshape model.
  • The RL policy was validated only with the archived v0.1.0 firmware, not the newer binaries.
  • Upstream disclaimer: research prototype, not validated for prolonged or heavy-duty use; tendons need periodic re-tensioning.

Simulate

Load it in the browser simulator and train a policy before building.

Open on humanoidrobots.training ↗

Next rung

Bittle / Bittle X →Petoi · quadruped · index 7.5

Easiest buildable quadruped, the next class up from hand. Adds gait generation.

NoteTetherIA rebranded to Chestnut Robotics (GitHub org renamed TetherIA -> Chestnut-Robotics). Design files are non-commercial; commercial manufacturing needs a license.

Sources

  1. [1]Aero Hand Open repo (specs, license TL;DR)checked 2026-09-24
  2. [2]Rebrand announcementchecked 2026-09-24
  3. [3]arXiv paperchecked 2026-09-24