Industry
Fastening for humanoid robots, joint actuators and dexterous hands
Embodied Intelligence Why it matters
A humanoid robot is a collection of joints that must move precisely, repeatedly and for a long time. Every one of those joints is a fastening problem: a pivot that has to locate two parts and carry rotation, a frame that has to be light but hold a thread, a transmission that has to keep preload while the load reverses thousands of times a minute.
The fastener content of a dexterous hand is concentrated in a very small space. Finger phalanges pivot on shoulder screws, linkage plates are clamped by M1.4–M2.0 machine screws, the frame is magnesium or aluminium reinforced with thread inserts, and every joint carries an anti-loosening element because the load never stops reversing. This is the segment where our engineering work is most concentrated, and it is one of the two industries this plant is built around.
3-in-1
Connection, location and rotation in one pin
>8.8
Insert strength grade
M0.8
Smallest precoated screw
150 °C
Aluminium bolt service temperature
Field problems
These are the failure modes we see most often, and the engineering response that addresses each one. Problems are stated as they appear on the line, not as they appear in a textbook.
| Problem observed | Engineering response |
|---|---|
| A finger joint develops play after a few hundred thousand cycles. | Play usually starts at the pivot. A ground shoulder screw carries the rotation on its shank instead of on the thread, and a straight shank does not wear the bore oval — which is the mechanism behind most lost repeatability. |
| Clamp screws lose preload because the joint load reverses continuously. | A pre-applied locking element — micro-encapsulated adhesive for a permanent joint, nylon patch where adjustment is needed — holds the preload without relying on a dispensed adhesive. |
| The magnesium or aluminium frame will not hold a thread through repeated assembly. | Thread inserts put a steel or brass thread into the light alloy. Carbon and stainless inserts reach grades above 8.8, so the insert is not the weak point of the joint. |
| A rigid clevis binds as the actuator moves off-axis through its stroke. | A rod end bearing at the push rod allows controlled multi-directional oscillation, so the actuator carries axial load instead of bending moment. |
| Aluminium and magnesium housings creep and lose preload when the joint runs hot. | A high-strength aluminium bolt expands at the same rate as the housing, so preload is retained. At 150 °C a steel bolt loses more than 96% of preload; the aluminium bolt loses 40–55%. |
| A joint that is stiff when new becomes loose, then stiff again as it wears. | That is usually two problems in one joint — a pivot wearing oval and a clamp screw relaxing. They are solved by different parts: a ground shoulder for the pivot, a locked screw for the clamp. |
Specification basis
A starting specification, not a fixed menu. Most programmes adjust one or two of these after the first joint review.
Joint pivot
Ground shoulder screws, stepped pins and locating pins
Frame thread
Thread inserts in magnesium, aluminium and plastic structures
High-strength screws
Grade 12.9 alloy steel and 14.9 anti-loosening; 10.9 / 12.9 titanium; 6.8 aluminium
Actuator joints
Rod end bearings for ball screw push rods and linkages
Anti-loosening
Precoated locking screws and lock washers for joints and transmissions
Finger-scale screws
M1.0 – M2.0 machine screws with locking elements
Frame positions
Torso frame, arm frame, leg load-bearing structures
Surface options
PVD, passivation, nickel, black oxide
Recommended products
Chosen for the tolerance, finish and locking requirements typical of the assemblies described above.
Pins & Spacers · Pivot & locating duties
Shoulder screws and precision pins for joints and motion structures — a ground shank that acts as a pivot or locating shaft while the thread clamps the assembly together.
Pins & Spacers · Actuator & linkage joints
Rod end bearings form the articulated joint at the end of a push rod or linkage, permitting controlled multi-directional oscillation without binding the actuator.
Thread & Panel · Light alloy & plastic
Thread inserts give a lightweight structure a thread that survives repeated assembly — wire thread inserts, self-tapping inserts and key-locking inserts for plastic, aluminium and magnesium.
Micro Screws · From M0.8 × 1.0 mm
Screws supplied with a locking, sealing or vibration-damping element already applied — micro-encapsulated adhesive, nylon patch, sealant or damping coating, from M0.8 upward.
Thread & Panel · Joint anti-loosening
Lock washers are among the core anti-loosening fasteners for robot joints and transmission systems, holding preload where vibration would otherwise relax the joint.
Thread & Panel · Lightweight joints
Cold-formed 7-series aluminium bolts that replace steel in magnesium and aluminium assemblies — removing galvanic corrosion and cutting fastener weight at the same time.
Design notes
These decisions are cheap at concept stage and expensive after tooling is cut.
01
In a pivot the unthreaded shank is the working surface. Its diameter, roundness and straightness decide whether the joint runs freely — a shoulder that measures correctly but is bent will still bind and wear the bore oval.
02
The cleanest joints use one element to locate and carry rotation, and a separate screw to clamp. Trying to make a single screw do both usually means the clamp load preloads the pivot and the joint becomes stiff.
03
Magnesium and aluminium need inserts for any thread that will be used more than a few times, and they need a fastener whose thermal expansion matches the housing if the joint runs warm.
04
A joint that reverses load cannot rely on friction alone. Precoated locking, lock washers or a captive design should be chosen at the drawing stage, because retrofitting an adhesive to an existing joint rarely controls the applied volume.
Joint review
A drawing gives us geometry. The mating material, the service cycles and the cleaning chemistry decide whether the joint works. Send all three and we will review the whole stack.
Questions
Answers to the questions that come up most in this industry.
Related industries
The same fastener discipline applies across these industries, with different documentation and validation requirements.
Industry
Our core business: machine and self-tapping screws, PVD finishes and precoated locking for phones, wearables, boards and precision modules.
Industry
Thread rolling screws, reinforcing inserts, pre-coated sealing screws and anti-galvanic protection for magnesium and aluminium die-castings that must be joined without losing the casting.
Industry
Locking washers, precoated screws, composite bonding and sealed riveting for aircraft where every gram matters and nothing may come loose.
From a single prototype joint to a PPAP production launch, the same team reviews the drawing and the assembly context.
