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
Joint Actuators & Drives
Fasteners for harmonic drives, cycloidal reducers and frameless motors
Joint Actuators & Drives Why it matters
Fasteners for harmonic drives, cycloidal reducers and frameless motors
A robot joint module packs a frameless motor, a harmonic or cycloidal reducer, an encoder and a brake into a cylinder the size of a fist. The fasteners have to clamp the reducer flexspline without distorting it, retain the rotor against torque reversal, and locate the encoder ring to within a few micrometres — all while the module heats to 70 °C in continuous duty.
We supply socket head and low-profile screws in 10.9 and 12.9 for reducer and housing joints, ground dowel pins for locating, and precoated screws for positions that see torque reversal. Because joint modules are usually assembled in small batches, we support lower volumes with the same documentation as high-volume electronics work.
M2 – M5
Joint module fastener range
12.9
Reducer clamp property class
h6
Locating pin fit available
70 °C
Continuous duty housing temperature
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 |
|---|---|
| Clamping the flexspline distorts it and increases transmission error. | Controlled preload with a specified torque and friction coefficient, plus flatness-checked washers to spread load. |
| Torque reversal loosens the reducer housing screws. | Encapsulated adhesive on 12.9 screws, with break-loose torque verified after a reversing-duty cycle test. |
| The encoder ring shifts and the zero position drifts. | Ground h6 dowel pins locating the ring to the housing, with position tolerance stack reviewed at design stage. |
| Aluminium housings creep under sustained preload at 70 °C. | Steel inserts or through-bolted joints, with relaxation data at temperature rather than room temperature. |
| A small batch of 200 joints does not justify a custom screw. | Standard diameter families with modified lengths and heads from existing tooling, at low minimum order. |
| The module must be non-magnetic for a collaborative robot. | SUS316 and titanium fasteners with permeability certification, and non-magnetic dowel pins. |
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
M2.0 – M5.0
Property class
10.9, 12.9, A4-80
Head style
Socket head, low profile, countersunk
Locating pins
h6 / h7 ground, straightness 0.01 mm/10 mm
Locking
Encapsulated adhesive for reversing duty
Temperature
Continuous 70 °C, peak 100 °C
Runout
≤ 0.02 mm on rotor retention faces
Documentation
Material cert, torque spec, relaxation 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 · M0.5 – 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
Precision Components · M1 – M4
Standoffs & Spacers
Male-female and female-female standoffs from M1 to M4, plus plain spacers, in brass, stainless and aluminium — with length tolerances that keep board stacks parallel.
Hex / roundBrass · SS · Al±0.05 mm length
Design notes
Four things to get right early
These decisions are cheap at concept stage and expensive after tooling is cut.
01
Reducer screws are a stiffness decision
The bolt circle stiffness affects transmission error. A higher property class helps, but a shorter grip length and a stiffer flange usually help more.
02
Pins locate, screws clamp
Do not rely on screw clearance to locate an encoder ring. Use dowel pins for position and screws only for clamp load — mixing the two functions wastes both.
03
Watch relaxation at temperature
Aluminium loses preload faster at 70 °C than at 20 °C. Ask for relaxation data at operating temperature if the joint is safety-relevant.
04
Low volume is normal here
Joint modules ship in hundreds, not millions. We support low minimums with standard tooling and modified lengths rather than requiring a new die.
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
Joint Actuators 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 torque for an M3 12.9 reducer screw?
Typically 2.0–2.4 N·m with a friction coefficient of 0.12–0.14 and a steel-to-steel joint. If the housing is aluminium, reduce to 1.5–1.8 N·m or use a steel insert. Verify on the actual joint.
Can you supply dowel pins in small quantities?
Yes. Ground pins from Ø2 to Ø8 in h6/h7 are available from a few hundred pieces, with straightness and roundness reports.
Do you offer non-magnetic joint hardware?
Yes, in SUS316 and titanium, including pins. We can certify relative permeability below 1.02.
How do you prevent loosening under torque reversal?
Encapsulated adhesive is the most effective single measure. For serviceable joints, a nylon patch plus a higher preload and a larger bearing area is the practical combination.
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 joint actuators programmes
From a single prototype joint to a PPAP production launch, the same team reviews the drawing and the assembly context.