Pins & Spacers
Articulated joints for linear actuators and linkage structures
Actuator & linkage joints · Pins & Spacers Overview
A linear actuator pushes in a straight line, but the mechanism it drives rarely moves in one. The rod end bearing is the part that reconciles the two: it sits at the end of the push rod and allows the joint to oscillate in several directions while the actuator extends and retracts. Without it, every misalignment between the actuator axis and the load becomes a bending moment in the rod.
In a humanoid robot these bearings are the core articulated components of linear actuator push rods and linkage structures. They are what make bionic motion possible: a finger or a limb driven by a ball screw push rod needs a joint that can follow a curved path, and a rod end provides exactly that controlled multi-directional movement without introducing play.
Function
Articulated joint for linear actuators and linkage structures
Motion
Controlled multi-directional oscillation within a defined angle
Typical position
End of a ball screw push rod, or within a linkage
Housing styles
Male (external thread) and female (internal thread)
Body materials
Carbon steel, stainless steel, alloy steel
Thread
Machine thread matched to the actuator rod
Design intent
Six engineering decisions that separate a micro fastener that works from one that merely fits the drawing.
Absorbs the angular misalignment between a linear push rod and the mechanism it drives, so the rod carries axial load instead of bending.
Permits oscillation in several directions within a defined envelope — the basis of natural, bionic articulation.
The standard joint at the end of a ball screw push rod, and in the linkage structures that transmit motion from it.
A rigid clevis binds as soon as the geometry moves off-axis. A rod end keeps the joint free through the full stroke.
It is a load-bearing structural part of the robot motion system, so material and thread quality are functional requirements.
Thread size, housing style and articulation angle are specified against the actuator so the joint and the rod are designed as one assembly.
Technical data
Reference data for design and sourcing. For a specific part, the drawing governs — these tables are the starting point for a joint review.
| Position | Function | Joint type | Design consideration |
|---|---|---|---|
| Ball screw push rod end | Transmits linear force to the limb | Male rod end | Must follow the limb arc through full stroke |
| Finger actuation linkage | Converts linear motion to finger flexion | Miniature rod end | Articulation angle must cover full grasp range |
| Limb linkage | Couples two moving segments | Female rod end | Load direction reverses each cycle |
| Wrist articulation | Allows multi-axis movement at the wrist | Male or female | Compact envelope limits housing size |
| Test rig and fixture | Connects actuator to test load | Standard rod end | Replaceable wear part |
Values are typical for the stated material and finish. Actual performance depends on the mating material, engagement length and assembly torque. Confirm with a sample test before design freeze.
Options
Mix these within one part number family. Where a combination is not manufacturable at your tolerance, we will say so at quotation rather than after the first lot.
Where it is used
Representative positions rather than an exhaustive list. Many of our parts are designed for one specific assembly and never appear in a catalogue.
| Assembly | Typical use |
|---|---|
| Humanoid limb actuator | Joint between the ball screw push rod and the limb segment |
| Dexterous finger drive | Miniature rod end converting tendon or push-rod travel into flexion |
| Parallel linkage | Two rod ends keeping a platform level through the stroke |
| Wrist articulation | Articulated joint allowing multi-axis movement at the wrist |
| Exoskeleton frame | Compliant joint between actuator and limb brace |
| Test fixture | Replaceable articulated joint in a fatigue rig |
Quality control
Inspection is not a final gate. It is a set of checks placed where a process can actually drift, with the result recorded against the lot code.
01
Thread gauge, GO / NO-GO
02
Articulation angle and freedom of movement
03
Housing dimensions against drawing
04
Material certificate per lot
05
Surface finish and plating thickness
06
Visual inspection for cracks at the housing
07
Assembly torque where supplied as a set
Questions
The questions our engineers answer most often on this product family.
Related products
These families are frequently used in the same assembly, or as an alternative when the joint requirement changes.
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.
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 · M0.6 – M2
Micro machine screws that engage a pre-formed thread — a tapped hole, a brass insert or a heat-set nut — and hold their clamp load through repeated disassembly.
Send a drawing or 3D model with the mating material and finish requirement. The reply is a process route, a tolerance review and a price — with the assumptions stated.
