Socket Head Shoulder Screw, Screw Manufacturer

We make socket head shoulder screws in carbon steel with an eco black zinc plate, a hex socket, a ground shoulder and a flat head face, quoted to the drawing. The head sits in a counterbore and the key drives it on axis, so head height and pocket depth are agreed together and the first article is seated in the bore.

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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 Socket Head Shoulder Screws Are

A socket head shoulder screw has a cylindrical head with an internal hexagon, a ground shoulder below the head and a smaller machine thread behind it. The part recorded here is carbon steel with an eco black zinc plate, quoted from M3 upward with the shoulder made to the drawing.

Socket head. A flat-topped cylindrical head with a hexagon inside it, driven with an Allen key.

Ground shoulder. A precision diameter that locates the part and sets how deep the head can sit.

Machine thread. A thread behind the shoulder that goes into a tapped hole or a nut.

They are used wherever a locating pivot has to be driven on axis and sit in a machined pocket, and they are the configuration most shoulder screws are drawn in. A socket head shoulder screw is also the easiest of the family to specify, because each of its features does one job and can be checked on its own.

The Counterbore Sets the Head Height

These socket head shoulder screws are usually fitted into a counterbored hole: a flat-bottomed recess machined into the plate, deep enough to take the head and wide enough to clear it. The depth of that pocket is what decides how much of the head stands above the surface, and the screw’s own head height is what the pocket has to be made to.

That is different from a countersunk screw, where the head is a cone and the depth is set by the angle and the countersink. A counterbore is a flat machining operation: the floor is square to the hole, and the head sits on it as a flat face against a flat face. The joint is more tolerant of a small depth error, because the head does not have to centre in a cone, but it is less self-centring: the clearance in the counterbore is what positions the head laterally.

The socket is what makes the head usable in a pocket. A wrench cannot reach a head that is below the surface, but a key can, because it enters from above on the axis. That is why the socket and the counterbore go together: the pocket removes the access a wrench needs, and the socket restores it.

The head face is then a pure bearing surface. It does not drive, it does not centre and it has no cone; it presses on the floor of the counterbore and spreads the clamp over the head area. On a part that is located by its shoulder and seated in a pocket, that is all the head has to do, and it does it without any of the compromises a low or countersunk head has to make.

The shoulder sets the rest. Its diameter locates the moving part, its length sets how far the head sits from the part, and the thread behind it holds the assembly. The three functions are separate here rather than combined, which is why this configuration is easy to specify and hard to get wrong.

Head, Socket, Shoulder and Thread

The part is quoted to the drawing with the head, the socket, the shoulder and the thread stated separately. Custom lengths up to 2,000 mm, subject to DFM review after drawing submission. The quotation for socket head shoulder screws carries the head diameter and height, the socket size and depth, the shoulder diameter and length, the thread, and the counterbore.

The head height and the counterbore depth are one pair. A pocket that is too shallow leaves the head proud; one that is too deep lets the head sink below the face and, on a joint where the head is meant to bear, takes away the bearing surface.

The socket size is fixed by the head diameter. Too large and the wall around the hexagon is thin; too small and the key cannot transmit what the thread needs.

The shoulder is agreed against the bore, and its length against the plate stack. On this configuration the shoulder length also sets how high the head sits above the part it locates, which feeds back into the counterbore depth.

What Socket Head Shoulder Screws Give and Costs

Four properties decide socket head shoulder screws, and each one carries a cost:

The value is a joint with no compromises: the head bears on a flat face, the key drives on the axis, and the shoulder locates. Each feature does one job, so a joint that works stays predictable.

The cost is machining. A counterbore has to be made in the customer part, and its depth and diameter have to match the head. A countersunk hole is easier to produce, which is why the countersunk version exists for parts that cannot take a counterbore.

Eco Black Zinc on a Socket Head

The recorded finish is eco black zinc, a trivalent black passivation over a zinc layer. It gives a dark, uniform head that disappears into a machined pocket, and sacrificial protection on a carbon steel part that is otherwise strong and inexpensive.

Surface Options for Socket Head Shoulder Screws

Inside the socket the plate matters for the key: a heavy layer reduces the effective across-flats, and a key that is a fraction too large will not enter. The socket is checked with the key after plating on a sample from each batch.

On the shoulder and the head face, the plate is a film inside the fit and under the bearing surface. Where the joint is tight, the drawing states whether the shoulder is masked or measured in the plated state.

Where Socket Head Shoulder Screws Are Used

Three assemblies where a locating pivot sits in a machined pocket:

Why Shi Shi Tong for Socket Head Shoulder Screws

Four reasons that matter on a part where the head, the socket and the shoulder each do one job, each tied to something the drawing or the first article proves. All four show in the sample.

How Socket Head Shoulder Screws Are Made

These screws are turned from carbon steel bar, with the cylindrical head turned and faced, the socket broached, the shoulder turned and ground, and the thread cut; the parts are then black zinc plated. The first piece of every run is measured on head diameter and height, socket across flats and depth, shoulder diameter and length, and thread.

The head face and the shoulder are turned in the same setup, so the face that bears in the pocket runs square to the diameter that locates. That is what makes the joint sit flat rather than on one edge, and it is the first thing checked on a sample.

The socket is cut after the head is faced, so its depth is taken from a finished surface. A socket cut too deep leaves a thin section over the shoulder, and a socket cut too shallow stops the key from engaging over its length.

Grinding the shoulder before plating keeps the locating diameter on a part that is not disturbed afterwards, and the plate then adds to it. The head face and the socket are checked in the plated state, because both are what the customer’s key and pocket meet.

Inspection: Head Face, Socket and Shoulder

What decides whether socket head shoulder screws pass is the head face, the socket and the shoulder. The inspection agreement covers those, and the criteria come from the drawing.

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

The head face is checked for flatness and for squareness to the shoulder. A face that is out of square sits on the floor of the pocket on one side, and the joint then rocks under load.

The socket is measured across flats and for depth, and checked with the key. A socket that measures right but will not take the key is usually a burr at a corner rather than a size problem.

The shoulder is measured for diameter, roundness and length. A sample is assembled into a counterbore of the specified depth to confirm the head sits as intended and that the joint is flat, which is the property the configuration exists to give.

Certificates and Material Documentation

Every batch of socket head shoulder screws is traceable to the bar 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 head and shoulder, and the plating report. The records carry the drawing revision and the batch number, so a repeat order of socket head shoulder screws seats the same way.

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 this configuration the first article is fitted into the counterbore and driven with the customer key. Buyers visit during the process to review samples.

Buyers and quality engineers visit for sample review, process discussion and supplier audits; the visit is arranged around production so the machining 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

What a Shoulder Screw Is How a stepped fastener locates a joint, and what the drawing has to state. Read the guide

Multi-Step Shoulder Screw Design When one shoulder is not enough, and what each step has to state. Read the guide

Products

Hex Socket Shoulder Screws The low head socket version in steel. Hex Socket Shoulder Screws	Hexagon Socket Shoulder Screws The hexagon socket head shoulder version. Hexagon Socket Shoulder Screws	Stainless Socket Shoulder Screws The stainless shoulder screw with a socket drive. Stainless Socket Shoulder Screws
Metric Precision Shoulder Screws The precision metric shoulder fastener series. Metric Precision Shoulder Screws	Shoulder Screws The socket head version in stainless. Shoulder Screws	Stainless Steel Shoulder Screws The stainless cap head version with a cross. Stainless Steel Shoulder Screws

Socket Head Shoulder Screw FAQ

Order Socket Head Shoulder Screws

How a socket head shoulder 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.