M3 Screw, Galvanized Pan Head Machine Screw

We make M3 screws in carbon steel with an eco blue zinc plate, a pan head and a Phillips recess, quoted to the drawing’s standard family. At M3 the family of the head decides whether it seats in a counterbore, so the family, the head and the plate are agreed before production.

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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 an M3 Screw Is

An M3 screw is a metric machine screw with a 3 mm nominal thread, made on this page in the pan head form with a Phillips recess. The part recorded here is carbon steel with an eco blue zinc plate, quoted with the length made to the drawing.

3 mm thread. The small end of the general-purpose range, used in electronics, instruments and small enclosures.

Pan head. A shallow dome with a flat bearing face and enough height for a full-depth cross.

Eco blue zinc. A trivalent zinc plate that protects the steel and gives the blue-white appearance common on small hardware.

They are used where a small fixing has to hold a plate, a cover or a bracket with a standard driver. An M3 screw is often the smallest size in a product’s bill of materials that still uses a conventional cross bit, which is why it survives in designs that have moved everything else to smaller hardware.

At M3 the Standard Family Matters More Than the Size

An M3 screw is small enough that a few tenths of a millimetre change the joint, and the dimensional standards that define pan head screws do not all agree at that scale. The JIS pan head, the DIN and ISO pan heads are all M3 machine screws with a cross recess, but their head diameters and head heights differ slightly, and at this size those differences are large enough to decide whether the screw seats in a counterbore or leaves a ring.

That matters when a product is copied or sourced from a different market. A housing designed around a JIS pan head has a counterbore sized for that head; a DIN pan head of the same thread will fit the hole but not the seat. The joint still assembles, so the error is not caught at assembly: it shows as a proud head, a ring pressed into the panel, or a washer that no longer fits.

The recess is the second part of the same problem. Standard families define the cross by a different reference, and a bit that suits one head may bottom or stand proud in the other. On an M3 head there is little material to absorb that, so the family and the recess belong together on the drawing.

The material and finish are the third. An M3 screw is usually carbon steel with a zinc plate, and the plate is a measurable fraction of a small head. A heavy plate closes up the cross and changes the effective head height, which is why the plated part is checked rather than the white one.

Those three together are why an M3 screw should be specified by standard and finish rather than by the words ‘M3 pan head’. The size is the least ambiguous part of the specification.

Head, Recess and Thread

The part is quoted to the drawing with the head, the recess and the thread stated separately. Custom lengths up to 2,000 mm, subject to DFM review after drawing submission. The quotation for an M3 screw carries the standard family, the head diameter and height, the recess, the thread, the length and the plate.

On an M3 screw the standard family is stated on the drawing for the reason above: it fixes the head diameter and height, and those are what the customer’s counterbore was made to.

The recess is checked with the matching bit. On an M3 head a plate that reduces the across-flats or fills the cross is enough to change which bit enters, so the recess is measured in the plated state.

The length is measured under the head and chosen so the thread engages fully. On a small screw the step from one length to the next is often enough to change a joint from solid to bottomed in a blind hole.

What an M3 Screw Gives and Costs

Four properties decide an M3 screw, and each one carries a cost:

The value of an M3 screw is a standard small fixing: a defined head, a standard bit, and a thread that suits a plate or a bracket without an insert.

On an M3 screw the cost is subtlety. The screw looks interchangeable with every other M3 pan head, and the differences that matter are in a standard document rather than in the part number, so a wrong family is usually discovered at the counterbore rather than at the drawing.

Eco Blue Zinc on a Small Pan Head

The recorded finish is eco blue zinc, a trivalent zinc plate with a blue-white passivation. On an M3 pan head it gives a bright finish and sacrificial protection, and it is the usual finish on small indoor hardware.

Surface Options for M3 Screws

On a small head the plate is a large fraction of the feature. A layer that adds a few microns to the cross walls changes which bit enters, and the same layer changes the head height by an amount that matters in a counterbore made for the unplated dimension.

That is why the drawing states which size applies to the delivered part. On an M3 screw the difference between the white and plated dimension is small in absolute terms and significant in the joint.

Where M3 Screws Are Used

Three assemblies where a small standard fixing is the requirement:

Why Shi Shi Tong for M3 Screws

Four reasons that matter on a screw whose specification lives in a standard document, each tied to something the drawing or the first article proves. All four show in the sample.

How M3 Screws Are Made

These screws are cold headed from carbon steel wire, with the pan head formed to the drawing’s family, the cross recess cut and the thread rolled; the parts are then blue zinc plated. The first piece of every run is measured on head diameter and height, face flatness, recess depth and width, thread and length.

The head is formed in a die made to the drawing’s family, so the head diameter and height come from the tool rather than from a later trimming operation. That is what makes the standard family a real property of the part: two dies produce two heads that look alike and fit differently.

The recess is cut after the head is formed, and its depth is set from the head height. On an M3 pan head there is enough material for a full-depth cross, but not enough to absorb a mistake: a recess cut too deep leaves a head that collapses under the bit.

The thread is rolled, and the parts are plated last. The recess and the head height are checked again in the plated state, and a sample from each batch is assembled with the customer bit.

Inspection: Head, Recess and Thread

What decides whether an M3 screw passes is the head, the recess and the thread. The inspection agreement covers those, and the criteria come from the drawing.

Head and recess on the projector	Thread and start checked
Core hardness checked	Salt-spray testing of the blue zinc

The head is measured for diameter and height against the family on the drawing, and the bearing face for flatness. On a small head a face that is slightly dished bears on its rim and leaves a ring on a painted panel.

On an M3 screw the recess is measured for depth and width and checked with the matching bit. On an M3 head a burr on one wall is enough to stop the bit, and the check is done with the bit rather than with a gauge alone.

The thread is gauged, and a sample is tightened in a test block at the customer’s plate thickness. That test shows whether the engagement suits the joint, which the screw’s own dimensions cannot tell.

Certificates and Material Documentation

Every batch of M3 screws is traceable to the wire it was made from and to the plating lot that finished it. The grade and heat number appear on the material certificate supplied with the parts, and the plating report carries the layer thickness and the lot number.

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

With each shipment we supply the material certificate, the inspection record for the dimensions on the drawing, including the family, head and recess, and the plating report. The records carry the drawing revision and the batch number, so a repeat order of M3 screws fits the same counterbore.

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 a small standard part the first article is checked in the customer’s counterbore, because the head family only shows there. Buyers visit during the process to review samples.

Repeat orders of M3 screws are checked against the same first article, so a head that fitted a counterbore once fits it again. Buyers and quality engineers visit for sample review, process discussion and supplier audits; the visit is arranged around production so the heading cell and the plating 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

Choosing Washer Head Screws When a wider bearing face is worth the height it adds. Read the guide

Plating Requirements for Screw Surface Treatment What a coating adds to a small head, and where it has to be kept out. Read the guide

Products

Brass Pan Head Screws The brass pan head version. Brass Pan Head Screws	Tiny Screws The tiny computer screw range. Tiny Screws	Small Screws The small stainless screw range. Small Screws
Micro Screws The micro machine screw family. Micro Screws	Tiny Screws for Sunglasses The pan head tiny screw family. Tiny Screws for Sunglasses	Miniature Shoulder Screws The smallest self tapping shoulder version. Miniature Shoulder Screws

M3 Screw FAQ

Order M3 Screws

How an M3 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.