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
Precision Components
Captive Screws
Spring-loaded and knurled captive screws that stay with the panel
M2 – M6 · Precision Components Overview
Captive Screws from M2 – M6
A captive screw cannot be lost. It is mechanically retained in the panel by a ferrule, a spring or a knurled shoulder, so when a service technician removes a cover the screw stays in the cover rather than falling into the machine. On a data centre floor or in an operating theatre, that difference is not cosmetic — a dropped M3 screw can short a board or contaminate a sterile field.
We supply spring-loaded captive screws, knurled thumb screws with a retaining ring, and panel-fastener assemblies with the ferrule and spring pre-assembled. The screw retracts into the ferrule when disengaged and protrudes when engaged, so the panel thickness determines the retracted length. Stainless is standard for corrosion resistance and for the non-magnetic behaviour that medical and instrumentation customers require.
Thread range
M2 – M6
Types
Spring-loaded, knurled thumb, panel fastener assembly
Panel thickness
0.8 – 6.0 mm
Retracted length
Matched to panel thickness + 0.5 mm
Head styles
Knurled, slotted, Phillips, Torx, low profile
Spring material
SUS304 or music wire, passivated
Design intent
What this product solves
Six engineering decisions that separate a micro fastener that works from one that merely fits the drawing.
Cannot be dropped
The screw is retained by a ferrule or spring assembly, so it stays with the panel through every service cycle.
Tool or hand operated
Knurled thumb heads for tool-free access, or recessed drives for controlled torque and tamper resistance.
Defined retraction
Retracted and extended lengths are matched to your panel thickness so the screw clears the mating thread when open.
Spring preload
A captive spring keeps the screw extended and provides light preload, preventing rattle in vibrating equipment.
Non-magnetic options
SUS316 and titanium assemblies for MRI, electron microscopy and other magnetic-sensitive environments.
Colour and finish matched
Black oxide, PVD and anodised finishes so the fastener disappears into the front panel.
Technical data
Captive screw selection by panel thickness
Reference data for design and sourcing. For a specific part, the drawing governs — these tables are the starting point for a joint review.
| Thread | Panel thickness (mm) | Head Ø (mm) | Retracted length (mm) | Drive | Typical equipment |
|---|---|---|---|---|---|
| M2.0 | 0.8 – 1.2 | 4.0 | 6 | Torx T6 | Instrument enclosures |
| M2.5 | 1.0 – 1.6 | 5.0 | 8 | Torx T8 | Rack-mount faceplates |
| M3.0 | 1.2 – 2.0 | 6.0 | 10 | Phillips 1 / T10 | Server chassis covers |
| M3.5 | 1.5 – 2.5 | 7.0 | 12 | Phillips 2 | Industrial control panels |
| M4.0 | 2.0 – 3.0 | 8.0 | 14 | Torx T20 | Medical carts |
| M5.0 | 2.5 – 4.0 | 10.0 | 18 | Hex 3 mm | Telecom cabinets |
| M6.0 | 3.0 – 6.0 | 12.0 | 22 | Hex 4 mm | Heavy equipment access panels |
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
Heads, drives, materials and finishes
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.
Head styles
- Knurled thumb — Tool-free, grip diameter 4–12 mm
- Knurled with slot — Hand tight plus screwdriver backup
- Low profile — Flush appearance on front panels
- Recessed drive — Torque-controlled, tamper resistant
- Shoulder head — Acts as its own retaining collar
Drive types
- Torx
- Phillips
- Slotted
- Hex socket
- Hand knurl
Materials
- SUS303
- SUS316 (non-magnetic)
- C3604 brass
- Aluminium 6061
- Ti-6Al-4V
Finishes
- Passivation
- Black oxide
- Electroless nickel
- Black PVD
- Clear anodise
Where it is used
Typical applications
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 |
|---|---|
| Server and storage chassis | M3 spring-loaded screws on hot-swap drive caddies |
| Rack-mount faceplates | M2.5 knurled captive screws for tool-free service |
| Medical device housings | M3 non-magnetic captive screws, cleanable surfaces |
| Industrial control panels | M4 captive screws with sealing O-ring |
| Test and measurement instruments | M2.5 low-profile captive screws |
| Telecom outdoor cabinets | M5 stainless captive screws with IP seal |
Quality control
What we measure on every lot
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
Retraction and extension length, functional gauge
02
Retention force, pull test 50 N minimum
03
Cycle life, 5,000 open/close
04
Spring force, load cell
05
Thread gauge, GO / NO-GO
06
Magnetic permeability where specified
07
Salt spray, 480 h for outdoor grades
08
Cleanability, surface roughness for medical
Questions
About captive
The questions our engineers answer most often on this product family.
Still deciding? Send the assembly drawing and the service condition.
We will recommend a size, finish and locking method — and tell you if a different
product family is the better answer.
What panel thickness do you need from me?
The panel thickness, the mating thread depth and the required retracted clearance. From those three we select a ferrule length and spring so the screw clears the thread when open and engages at least three full threads when closed.
Are captive screws repairable?
Spring-loaded types can be disassembled and the screw replaced if the ferrule is not swaged. Swaged panel fasteners are permanent and require replacing the whole assembly. Tell us whether field replacement is a requirement.
Can they be sealed against water?
Yes. An O-ring under the head gives IP65–IP67 protection when the screw is tightened to the specified torque. The O-ring material must be matched to the cleaning chemistry — EPDM for water, FKM for solvents.
Do you offer non-magnetic versions?
Yes. SUS316 and titanium assemblies are effectively non-magnetic and are used in MRI surrounds and electron microscopy. We can supply permeability test data.
Related products
Often specified together
These families are frequently used in the same assembly, or as an alternative when the joint requirement changes.
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
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
Specialties · M0.8 – M6
Security & Tamper-Proof Screws
Tamper-resistant micro screws with pin-in-Torx, tri-wing, pentalobe and one-way drives — for products where access must be controlled or evidenced.
Pin-in-TorxTri-wingPentalobe
Need captive to your drawing?
Send a drawing or 3D model with the mating material and finish requirement. We reply with a process route, tolerance review and price — usually within two working days.