Precision Components · Ø1.0 – Ø10 mm
Shoulder Screws & Pins
Precision shoulder screws, dowel pins and stepped pins ground to h9 for pivot, locating and alignment duties in miniature mechanisms.
h9 ground shankPivot & locatingStainless / alloy
Industry
Robotics & Dexterous Hands
High-strength micro fasteners for fingers, joints and tendon drives
Robotics & Dexterous Hands Why it matters
High-strength micro fasteners for fingers, joints and tendon drives
A dexterous hand is the hardest fastening environment in robotics. The fingers are the size of a human finger, so the screws are M1 to M2.5. The joints reverse direction thousands of times per hour, so any fastener that loses preload becomes a rattle, then a backlash error, then a failure. And the whole assembly sits in the magnetic field of a joint motor, so a loose screw is not just a mechanical problem.
We work with robotics teams on three levels: the finger linkage, where M1.4–M2.0 high-strength screws and ground shoulder pins locate the phalanges; the tendon and pulley path, where precoated screws hold idlers and tensioners; and the palm and wrist, where M2.5–M4 screws clamp actuator housings and heat spreaders. For each position we look at the load direction and cycle count before recommending a locking method.
10⁷
Target cycle life for finger joints
M1.4
Typical phalanx screw size
h7
Shoulder pin fit for pivots
12.9
Highest property class used
Field problems
What actually goes wrong in this industry
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 |
|---|---|
| Finger joint screws loosen after a few hundred thousand cycles and introduce backlash. | Encapsulated adhesive or nylon patch at a controlled thread position, with break-loose torque verified after cycling. |
| A shoulder screw with good diameter but slight bend binds in the phalanx bore. | Straightness held at 0.01 mm per 10 mm in addition to h7 diameter, with Ra 0.2 ground finish. |
| The screw head interferes with the tendon path. | Low-profile and wafer heads, or countersunk screws flush with the linkage plate. |
| Aluminium linkage plates strip their threads after repeated service. | Threaded inserts or steel standoffs in the aluminium plate, with pull-out tested in the actual alloy. |
| Magnetic joint motors attract loose ferrous fasteners. | SUS316 or titanium fasteners with permeability data, plus captive or precoated designs to prevent loosening. |
| Every gram of finger mass increases actuator torque demand. | Titanium and aluminium fasteners where strength allows, with mass quoted per screw on the drawing. |
Specification basis
Typical requirements for this industry
A starting specification, not a fixed menu. Most programmes adjust one or two of these after the first joint review.
Diameter
M1.0 – M4.0, M1.4–M2.0 in fingers
Property class
10.9 / 12.9 steel, A4-80 stainless, Grade 5 titanium
Locking
Encapsulated adhesive preferred, nylon patch for serviceable joints
Head style
Low profile, wafer, countersunk flush
Shoulder pins
h7 ground, straightness 0.01 mm/10 mm, Ra 0.2
Magnetic
Non-magnetic SUS316 / titanium available
Testing
Cycle life, break-loose after cycling, backlash measurement
Documentation
Material cert, torque spec, permeability data
Recommended products
Families we specify most in this industry
Chosen for the tolerance, finish and locking requirements typical of the assemblies described above.
Micro Screws · M0.8 – M6
Precoated Screws
Screws with a factory-applied locking or sealing element, so the assembly line receives a ready-to-drive fastener with no liquid adhesive and no cure time.
Nylon patchMicro-encapsulated3M tape
Micro Screws · M0.8 – M6
PVD Coated Screws
Physical vapour deposition coatings that add 2–5 µm of hard ceramic film — for driver wear resistance, low friction and decorative black or gold finishes.
2–5 µm filmTiN · CrN · DLCHV 1800+
Micro Screws · M0.5 – M6
Machine Thread Micro Screws
Precision machine screws from M0.5 to M6 with rolled Class 6g threads, tight head concentricity and clean drive recesses for automated driving.
Class 6g threadRolled threadStainless / carbon steel
Design notes
Four things to get right early
These decisions are cheap at concept stage and expensive after tooling is cut.
01
Design the joint for service, then lock it
A finger joint will be opened during development many times. Use nylon patch during prototyping and encapsulated adhesive for production, and document the change.
02
Backlash is a fastener problem
Much of the backlash blamed on gears is actually joint clearance. A ground shoulder pin with the right fit removes more error than a higher-precision gearbox.
03
Mass compounds along the chain
A 0.3 g saving at the fingertip is worth more than 3 g at the palm because it reduces the torque every upstream actuator must supply.
04
Test to the real cycle count
A million cycles is a week of continuous operation in some labs and a year in others. Specify the number and the direction of loading, not just "long life".
Joint review
Send us the assembly, not just the screw
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.
- Tolerance stack and fit check
- Torque and preload recommendation
- Material and finish selection
- Locking method and service strategy
Questions
Robotics fastening FAQ
Answers to the questions that come up most in this industry.
Have a specific joint? Send the section drawing and the service
condition. We will reply with a recommended fastener and the reasoning behind it.
What fastener do you recommend for a phalanx pivot?
A ground shoulder screw in h7, SUS420 hardened to HRC 48–52, Ra 0.2, with a radiused under-head transition and a nylon patch on the thread. For a non-magnetic requirement, titanium with a polymer bushing.
How do I stop finger screws loosening?
Encapsulated adhesive is the most reliable for a permanent joint. If the finger must be serviceable, use a nylon patch and verify break-loose torque after the target cycle count rather than only at assembly.
Can you supply non-magnetic fasteners?
Yes. SUS316 and Ti-6Al-4V are effectively non-magnetic. We can supply relative permeability data and, where needed, certify each lot.
What is the smallest high-strength screw available?
M1.2 in alloy steel at property class 10.9, or M1.4 at 12.9. Below M1.2 the case depth becomes a large fraction of the core and the property class is no longer meaningful.
Related industries
Adjacent platforms
The same fastener discipline applies across these industries, with different documentation and validation requirements.
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Engineering support for robotics programmes
From a single prototype joint to a PPAP production launch, the same team reviews the drawing and the assembly context.