Industry
Cleanable, non-magnetic and traceable fasteners for instruments
Medical & Analytical Devices Why it matters
Medical and analytical devices combine two requirements that are individually common but together restrictive: the fastener must be corrosion resistant and cleanable, and it must not disturb a magnetic or optical field. An MRI surround cannot contain a ferromagnetic screw; an electron microscope cannot tolerate outgassing from a lubricant; a surgical instrument must survive repeated autoclave cycles without seizing.
We supply SUS316L, titanium and PEEK-compatible fasteners with passivation, low-outgassing finishes and optional non-magnetic certification. For instruments that are repeatedly sterilised, we recommend a dry-film lubricant or a PVD coating rather than oil, and we can supply cleanliness and outgassing data for the finished part.
SUS316L
Standard medical stainless
<1.02
Relative permeability available
134 °C
Autoclave cycle temperature
ASTM E595
Outgassing testing available
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 fastener becomes magnetic after cold heading and disturbs an MRI field. | SUS316L with solution annealing and permeability testing, or titanium, with certification per lot. |
| Autoclave cycles cause stainless screws to seize in stainless threads. | Passivation plus a dry-film or PVD lubricant, with galling tested over repeated autoclave cycles. |
| Lubricant outgasses and contaminates an optical path. | Solvent-free dry-film coating or DLC, with ASTM E595 outgassing data supplied. |
| Debris trapped in a drive recess cannot be cleaned. | Open recess geometry and electropolished surfaces, with cleanability validated by the device manufacturer. |
| A notified body audit requires material and process traceability. | Lot traceability to melt number with material certificates and process records. |
| A tiny instrument mechanism needs an M0.8 screw in titanium. | Grade 5 titanium micro screws from M0.8, with matching titanium or polymer bushings to avoid galvanic couple. |
Specification basis
A starting specification, not a fixed menu. Most programmes adjust one or two of these after the first joint review.
Diameter
M0.8 – M5.0
Material
SUS316L, SUS304, Ti-6Al-4V, PEEK
Magnetic
Non-magnetic grades, permeability < 1.02
Finish
Passivation, electropolish, DLC, dry-film
Sterilisation
Autoclave, ETO, gamma compatibility
Cleanliness
Degreased, particle-count data available
Outgassing
ASTM E595 where optics are present
Traceability
Melt number, material cert, process record
Recommended products
Chosen for the tolerance, finish and locking requirements typical of the assemblies described above.
Micro Screws · M0.5 – M6
Precision machine screws from M0.5 to M6 with rolled Class 6g threads, tight head concentricity and clean drive recesses for automated driving.
Precision Components · Ø1.0 – Ø10 mm
Precision shoulder screws, dowel pins and stepped pins ground to h9 for pivot, locating and alignment duties in miniature mechanisms.
Precision Components · M2 – M6
Captive panel screws that remain attached to the cover when opened — eliminating lost fasteners in field service, medical and rack-mount equipment.
Micro Screws · M0.8 – M6
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.
Design notes
These decisions are cheap at concept stage and expensive after tooling is cut.
01
Austenitic stainless can become slightly magnetic after heading. If the device is magnetic-sensitive, specify solution annealing and permeability testing rather than assuming the grade is enough.
02
Stainless-on-stainless threads seize after repeated sterilisation. A dry-film lubricant or a dissimilar material pairing solves it more reliably than tightening less.
03
A deep, narrow drive recess cannot be cleaned reliably. Where cleanliness is critical, choose an open drive and avoid blind holes.
04
Two SUS316L screws with different passivation can behave very differently in corrosion testing. Specify the passivation standard and the acceptance test.
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.
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Our second focus industry: M1–M4 high-strength fasteners for dexterous hands, finger linkages and tendon-driven mechanisms, where fasteners see millions of cycles.
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M2–M5 fasteners and precision pins for robot joint modules — clamping reducers, retaining motor rotors and locating encoder rings.
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The smallest fasteners we make: M0.5–M1.6 screws, micro standoffs and inserts for phone modules, earbuds, smartwatches and AR glasses.
From a single prototype joint to a PPAP production launch, the same team reviews the drawing and the assembly context.