M3×360 Black Stainless Steel Machine Screws

One screw, one length, one coating: an M3 machine screw long enough to pass through a whole stack of components and still leave usable thread. The length is the easy part to state and the hardest part to hold — a 360 mm M3 shank bends under its own weight, so straightness, thread run-out and the coating on the thread decide whether it assembles.

What This Screw Actually Has to Do

Black electrophoresis over stainless steel: the coating is applied after the thread is rolled, so the thread fit is set by how much film the coating adds. The PF head carries a Phillips recess and an under-head fillet, which spreads the bearing load on a thin panel instead of denting it.

• Length reference. The 360 mm is measured under the head, not overall. On a screw this long the difference between the two references is enough to miss the last thread in the assembly.
• Straightness. Rolled M3 wire at this length has a natural bow; it is straightened and then gauged on a surface plate, not judged by eye on the bench.
• Coating on the thread. Electrophoresis deposits on every surface including the flanks; the film thickness is capped so a standard nut still runs down the full length by hand.

Why 360 mm Changes the Problem

A short screw is a fastener; a 360 mm M3 screw is a rod that happens to have a head and a thread. Three things go wrong that never show up on short parts:

• It deflects while being pushed in. Any misalignment between the clearance holes in the stack turns the shank into a spring. The entry chamfer and the straightness of the first 100 mm matter more than the thread itself.
• It whips during thread rolling. Long slender parts need support along the length, otherwise the thread run-out grows toward the tail and the nut binds halfway.
• It bends in packing. Cartons that are fine for M6 will bow an M3 × 360 mm bundle; the parts then read as “out of straight” at the customer, even though they left the line within tolerance.

Where the Length Is Measured

The drawing reference sets everything downstream: under-head length is what the assembly stack needs, overall length is what a caliper reads on the bench. We confirm the reference on the drawing before the first piece, and both numbers go on the inspection record so the receiving inspection measures the same thing we did.

Stainless and Black Coating Together

Stainless gives the corrosion margin; the black electrophoresis gives the appearance and a second barrier in wet or cleaning-agent environments. The combination has two practical limits:

• Thread fit after coating. Film builds on the flanks as well as the crests. We keep the coating thin enough that a standard nut runs on by hand and specify the class on the drawing.
• Touch-up at the head. Driving a Phillips bit can mark the recess. The coating is hard enough for normal assembly torque; for high-volume lines we agree a bit type and torque window up front.

Entry Through a Stack of Components

Long screws are usually the last part of an assembly and the first place a misalignment shows. Two drawing details remove most of the risk: a chamfer or lead-in on the entering end, and a clearance-hole tolerance that is called out per plate rather than as one stack value. If the stack is more than three plates, we ask for the hole positions rather than a single clearance figure.

Inspection on a Long Part

The checks that matter are the ones a short-part gauge cannot see: straightness over the full length, thread run-out at the tail, coating thickness on the flanks, and the under-head length. Each batch carries those four numbers plus the visual acceptance on the coating.

Where This Length Is Used

Three assembly positions where a 360 mm M3 screw solves a real problem, and what we hold on each one.

Electrical enclosures and control cabinets

The screw runs the full height of a cabinet, through standoffs and sheet-metal plates, to a single nut at the back. Misalignment between plate holes is normal; the screw has to find its way without cross-threading. What we control: straightness over the first 100 mm, an entry chamfer, and coating thickness on the thread so the nut runs by hand.

Outdoor equipment and lighting

Fittings that live outside see rain, cleaning agents and temperature swing. Stainless carries the corrosion duty; the black film keeps the appearance and stops galvanic marks where the screw meets painted aluminium. What we control: film build on the flanks, adhesion after forming, and a coating tone agreed against a physical sample.

Display, signage and light structures

Long thin screws in display frames are visible, so the head and the coating are part of the design. They also have to stay straight through transit. What we control: head profile and recess depth, straightness before packing, and tube packing that supports the shank instead of loading the head.

MANUFACTURING

Single-die and multi-station capacity in one floor

From M0.8 to M16, from 0.4 mm to 2,000 mm, cold heading and CNC turning under one roof.

INSPECTION

Drawing-driven inspection for every batch

Dimensions, recess fit, plating thickness, and torque-to-failure checks are recorded per batch.

GO/NO-GO thread gauging	Optical profile check
Hardness testing	Salt-spray testing

Inspection follows the drawing and the agreed inspection plan; records are kept per batch.

Certificates and Reports

CERTIFICATES

ISO 9001:2015 certified, full documentation per shipment

Material certificates, dimensional reports, and surface treatment records are issued for the tested items.

ISO 9001:2015	RoHS
Patent	Trademark

Where Torx Socket Cap Screws Are Used

Carbon steel yellow-zinc torx cap screws are a general-purpose industrial fastener, but they are not fitted everywhere. These are three assembly positions where the drive and the shoulder step actually earn their place, and what we hold on each one:

Motor terminal boxes and drive covers

The screw seats on the machined aluminium cover of a motor terminal box. The shoulder step enters the cover hole first, so the lid locates before the thread bites and the cover cannot shift while it is being tightened. What we control: head height against recess depth, step diameter against the cover hole, and plating thickness on the thread so the screw still runs in a coated cover without galling.

Motor terminal box — the Torx head seats on the machined cover and the shoulder step locates the lid before the thread engages.

Inverter and charger cabinet panels (fixed installations)

Three screws hold a powder-coated side panel onto an inverter frame; the copper busbars and the terminal block sit behind that panel, so the panel comes off for service more than once a year. A Torx recess survives that repeated removal without wallowing out. What we control: drive size against the recess, thread length against the panel-plus-frame stack, and yellow zinc thickness against the corrosion class agreed for the cabinet.

Inverter cabinet — panel screws sit above the busbar compartment; the recess stays serviceable after repeated removal.

Analytical instruments and laboratory housings

On a benchtop analyser the same screw fixes the brushed stainless side panel. Here the head has to sit low enough not to catch a wipe-down cloth, and the yellow-zinc tone has to stay consistent across the batch because the heads are visible on the finished instrument. What we control: head profile against the panel face, step length against sheet thickness, and colour consistency of the plating from batch to batch.

Analytical instrument — stainless side panel fixed with the same screw, head kept low and flush to the panel face.

Technical FAQ — Torx Socket Cap Screws

Working with Shi Shi Tong

CUSTOMERS

Repeat business is the largest part of our order book

Customers visit the factory for sample approval, production review and shipment inspection — and most of the next order comes from the same accounts.

Customer visit — production review	Customer audit on the shop floor	Customer touring the Shi Shi Tong shop floor	Denmark customer visiting Shi Shi Tong
Shi Shi Tong at international exhibition	Customer delegation at Shi Shi Tong	Customer team visiting Shi Shi Tong	Customer reviewing first-article parts with our QC team

Technical FAQ

Is the 360 mm measured under the head or overall?

Under the head is the standard reference for this part because that is what the assembly stack needs. Both numbers are printed on the inspection record so receiving inspection measures the same one.

Will a standard nut run on after the black coating?

Yes, provided the film thickness stays inside the class on the drawing. The coating is capped so the nut runs down the full thread by hand; we confirm on the first article.

How straight is a 360 mm M3 screw?

Straightness is gauged over the full length on a surface plate, not by eye. The value is recorded per batch, and packing is designed so transit does not add bow.

Can the point be chamfered for easier entry?

Yes. A lead-in chamfer or a dog point is a drawing option and is the usual fix when a screw crosses several plates.

What is the minimum order for a coated long part?

It depends on the coating batch and the packing method; send the length, the stack and the annual quantity and we quote against the drawing.

Send the Stack, Not Just the Length

Tell us the plates the screw passes through, the thread engagement you need and the coating reference. We will confirm the under-head length, the straightness call-out and the thread class before quoting.

Send us your drawing