M3×360 Black Stainless Steel Machine Screws

We manufacture black stainless steel machine screws in long lengths, including the recorded M3 x 360 mm part, cold headed in a split die with a PF head, a Phillips recess, a partial machine thread and an electrophoretic black coating. Head diameter, thread length, coating thickness and the thread fit after coating are taken from your drawing.

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ISO 9001:2015 · Manufacturing since 1998 · 8,678+ customers · 89 countries and regions

Made to order – there is no stock catalogue. Each part is produced to your drawing, and production starts after drawing review and first-article approval.

What Defines a Black Stainless Steel Machine Screw

A black stainless steel machine screw is a screw with a machine thread, a cross recess and a dark coating applied after the thread is formed. The recorded item on this page is M3 × 360 mm: a long, slender body with a PF head, a Phillips recess, a partial thread at the tip and an electrophoretic black finish. Head diameter, thread length and coating thickness are set from the drawing, not from a stock list.

Long shank. At 360 mm on an M3 body the part is slender enough that it has to be supported while it is made and packed straight while it travels. The plain section passes through clearance holes and spacers, so the thread reaches a tapped block at the far end of the stack.

PF head. A pan-framing profile: a low head with a wide, flat bearing face. It sits lower than a standard pan head and spreads the clamp load across a thin panel instead of denting it around the hole.

Partial thread. The thread is rolled on the leading section only. The plain shank behind it is the working length through the stack, and the drawing fixes where the thread starts relative to that length.

Black coating. The colour comes from an electrophoretic coating, not from the alloy. Stainless keeps its own corrosion resistance underneath; the coating is there for appearance, for contrast against bright parts and for a dark finish on visible fixings, and it has to leave the thread usable.

Together these decide the joint: the head bears on the panel, the long shank reaches through the stack, the partial thread engages the tapped part, and the black finish has to survive both the driver and the assembly. That is why a black stainless steel machine screw is specified by head, thread position, coating and length together.

Stainless Body, PF Head and Electrophoretic Black

The body of this black stainless steel machine screw is stainless wire, with 304 and 316 the common grades and the heat number kept with the batch record. The grade is fixed on the drawing because it decides what the part does under the coating: on a wash-down assembly the alloy is the corrosion barrier, and the black film only covers it.

The PF head is upset in a split die that closes around the shank. That support is what keeps the head square to a long, thin body; a head that is a fraction off square shows as a gap under one side when the screw is tightened against a panel.

Below the head the shank runs plain for most of its length, then the partial thread is rolled on the leading section. The plain diameter is held so it clears the holes it passes through rather than gripping them, and the thread at the tip is gauged for size and pitch.

The black finish is applied last. The parts are cleaned and passivated, coated in an electrophoresis bath, cured, and then the thread and the recess are checked again, because a film that is uniform on a flat face is still a film on a thread flank. The sequence matters: thread first, coating second, gauge after coating.

Sizes, Lengths and Tolerances

Black stainless steel machine screws of this family are quoted from M1 to M10 and in lengths set per drawing; the recorded item on this page is M3 × 360 mm with a partial thread. Custom lengths up to 2,000 mm are subject to DFM review after drawing submission, because the tooling, the thread roll and the packing all change with the length.

Each size is quoted against the stack the screw passes through. The plain shank length, the clearance holes and the thread engagement at the far end are reviewed together, because a long screw that runs out of plain shank grips the stack instead of clamping it, and one with too little thread left in the tapped block works loose.

Length is measured from the bearing face rather than from the top of the head, and the thread length from the tip. Those two datums are stated on the drawing because the same nominal length reads differently depending on where it is taken from.

The PF Head, the Phillips Recess and the Partial Thread

The PF head is the feature that decides how this screw sits. It is a low head with a wide, flat bearing face, so the load goes into the panel over a larger area than a standard pan head and the head stands less proud of the surface. On a visible black panel that combination is what keeps the fixing flat and the colour continuous.

The Phillips recess is formed in the head and driven with a standard bit. On a coated part the recess is where the film is most awkward: the coating fills the corners of the cross, so the recess has to be formed deep enough that the bit still seats after coating, and the driver is checked on a coated sample rather than on a bare one.

The partial thread is rolled on the leading section, and the plain shank above it is what makes a long screw work as a through-fixing. The thread start is fixed relative to the bearing face, so the plain length that clears the stack is the same on every part in the batch.

A 360 mm body on M3 is a slender part, so it is headed in a supported die and handled in trays between operations. It is packed straight, in tubes or in trays with the shanks supported, because a long screw that takes a set in transit is difficult to start in a deep stack.

Electrophoretic Black: Coverage, Thickness and Thread Fit

The black finish on a black stainless steel machine screw is an electrophoretic coating. The parts are immersed in a bath and a direct current deposits the film onto the surface, then the coating is cured. Because the film is deposited electrically rather than sprayed, it covers the whole immersed surface: the head face, the recess, the shank and the thread flanks.

That even coverage is also the risk. A film on a thread flank changes the fit, so the thread is gauged after coating rather than before, and the drawing states the class the part has to meet in its finished condition. On thin parts the coating is kept thin for the same reason: enough to give a uniform black, not enough to close the recess.

On stainless the coating is not carrying the corrosion duty. The alloy does that, and the film is there for appearance and for abrasion resistance on a visible face. It still has to hold on edges and around the recess, which is why the parts are cleaned and passivated before coating and the cure is controlled afterwards.

Finish Selection for Black Machine Screws

Salt-spray exposure is agreed per project and written on the drawing. On a coated stainless part the test is run on the finished condition, because the film, not the alloy alone, is what the customer sees and touches.

Packing protects the coating as much as the thread. Long parts are packed straight and separated so the black faces do not rub against each other, and the label carries the batch, the material heat and the coating batch.

Where Black Stainless Steel Machine Screws Are Used

Three assemblies where a long black screw has to reach through a stack and still look right on the face:

Welded steel frames and guard structures Where it sits The screw passes through a frame member and a guard panel before the thread engages a tapped block, with the black head left visible on the outside face. When it goes wrong A head that stands proud catches on a moving part, and a shank that will not pass through the stack stops the frame from closing up. Why it happens The stack is deep, the frame is welded and not re-machined, and the head is seen on the finished machine. What we control Head diameter and head height checked, plain shank measured to the stack, and the first article assembled in the frame.

Long black screws through a welded steel frame

Black equipment panels and cabinet frames Where it sits The screw holds a coated panel or a bracket to a cabinet frame, where the black head is part of the visible finish. When it goes wrong A coating that chips at the recess leaves a bright ring on a black panel, and a head that is too tall breaks the flat face. Why it happens The panel is thin, the colour is specified to match, and the joint is opened for service. What we control Coating checked on the recess and on the head edge, and the driver matched to the coated recess.

Black heads kept flush on a coated equipment panel

Machine frames and multi-layer plate stacks Where it sits The screw runs through several plates and spacers with the thread engaging only the last block, so the plain shank carries the whole stack. When it goes wrong A shank that grips the plates pulls the stack out of line, and a thread that starts too early leaves nothing to clamp at the far end. Why it happens The stack is made of ground plates, the holes are reamed, and the screw sets the alignment of the assembly. What we control Plain shank length and thread start measured on the first article, then the part is assembled in the stack sample.

A long screw through a multi-layer plate stack

Why Shi Shi Tong for Black Stainless Steel Machine Screws

Four reasons that matter when a long, coated screw has to pass through a stack and still present a clean black face:

How These Screws Are Manufactured

Shi Shi Tong forms these black stainless steel machine screws on a split-die header: the die closes around the wire and supports the shank while the PF head is upset, the partial thread is rolled on the leading section, and the parts are passivated, coated and cured before the final gauge check. The first part of every run is measured on the head, the plain shank and the thread, and driven with the matching bit, before the batch continues.

Between runs the die is changed to the drawing head and the thread roll to the size; the first part goes to the projector and the gauges before the run continues. Coated parts are handled in trays from the oven to the packing table so the film is not marked while it is still settling, and long parts are packed straight so the shank does not take a set between the machine and the assembly.

Inspection: Head, Thread After Coating and Film

What decides whether a black stainless steel machine screw passes is not only the thread: it is the head diameter and height, the recess after coating, the thread class after coating and the film itself. The inspection agreement covers those, and the criteria come from the drawing and the coated sample.

Head and shank on the projector	Thread gauged after coating
Hardness testing where the drawing requires it	Salt-spray testing of the coated part

Each batch is recorded against the drawing revision: head and shank from the first article, the thread gauged after coating, the recess checked with the driver, and the coating batch carried on the label. If a gauge or the recess check fails, the parts back to the last good setting are held and re-checked.

If the material or finish needs an outside test, the request is set at the drawing stage, and the report ships with the parts under the batch number.

Certificates and Material Documentation

Every shipment of black stainless steel machine screws is traceable to the wire it was made from. The grade, heat number and standard are recorded on the material certificate supplied with the parts, and the inspection records follow the criteria agreed on the drawing.

ISO 9001:2015	RoHS test report
Registered trademark	Patent: security screw and driver

With each batch we supply the material certificate, the inspection record for the criteria on the drawing and, where it is listed, the third-party report for the material or the coating. The documents carry the drawing revision and the batch number, so the paperwork can be matched to the parts.

Customers and Projects

More than 8,678 customers in 89 countries and regions have ordered from Shi Shi Tong; 87% of orders come from repeat customers and 56% through referrals. Most projects follow the same route: drawing review, first-article approval, then batches checked against that sample. On coated long parts the first article is approved in the assembly it was drawn for, so the plain shank, the thread start and the black face are signed off as a set. Buyers visit during the process to review samples and to see how the heads are formed and how the coated parts are packed.

Buyers and quality engineers visit for sample review, process discussion and supplier audits; the visit is arranged around production so the header and the coating line can be seen on the day the parts run.

Customer group visit – sample review	Customer group visit – process discussion	Customer group visit – factory tour
Customer visit – project kick-off	Danish customer – drawing review	Industry exhibition – meeting customers

Related Products and Guides

Technical Guides

Long Thin Screws: Drawing and Manufacturing Requirements What to put on the drawing for long, thin parts: datum, shank, thread position and handling. Read the guide

How Long Does It Take to Customize Extra-Long Screws? Where the time goes in a custom long-screw order, from drawing review to first article. Read the guide

Products

Custom Extra-Long Machine Screws Family page: mixed heads, drives and finishes up to 2,000 mm. Custom Extra-Long Machine Screws	Partial Thread Machine Screws Partial-thread machine screws with a defined plain shank. Partial Thread Machine Screws	Extra-Long Low-Profile Phillips Screws Low heads with a PH recess for recessed covers and black chassis panels. Extra-Long Low-Profile Phillips Screws
M6 Pan Head Hex Socket Machine Screws Socket-driven pan head screws up to 630 mm with a partial thread. M6 Pan Head Hex Socket Machine Screws	Extra-Long Hex-Head Dacromet Screws Long hex-head screws with a Dacromet coating for wet or outdoor assemblies. Extra-Long Hex-Head Dacromet Screws	Countersunk Socket-Slotted Screws with Locking Patch Sunk heads with a combined socket-slot drive and a nylon locking patch. Countersunk Socket-Slotted Screws with Locking Patch

Black Stainless Steel Machine Screws FAQ

Order Black Stainless Steel Machine Screws

How a black stainless steel machine screw project runs from drawing to repeat delivery:

Each step is confirmed with you before the next one starts; the drawing revision from the first article is what repeat orders are checked against.