Hex Socket Shoulder Screw Custom Factory

We make hex socket shoulder screws in carbon steel with a zinc plate and a low head, quoting the shoulder diameter and length to the drawing. The shoulder fit and the socket depth are agreed as one set, and the first article is fitted into your 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 Hex Socket Shoulder Screws Are

A hex socket shoulder screw combines a socket head with a precision unthreaded shoulder, so the shoulder locates or pivots while the socket applies the clamp. The part recorded here is carbon steel with a zinc plate and a low head, quoted with the shoulder dimensions made to the drawing.

Shoulder. A ground diameter between the head and a smaller thread, acting as the bearing or locating surface.

Hexagon socket. An internal hexagon driven with a key, held in whatever height the head allows.

Low head. A reduced head height so the top of the fixing sits close to the surface, which is the reason this form exists.

Zinc plated steel. A sacrificial finish at a lower cost than stainless, chosen where the joint is dry and cost matters.

They are used in mechanisms where a plate slides over the fixing, in low-clearance pivots, and in fixtures where the head must be as low as possible without losing the locating shoulder.

Low Head and Shoulder Pull Against Each Other

A shoulder screw has two jobs: the shoulder locates, and the head clamps. A low head makes the second job harder, because the material available above the shoulder is what holds the hexagon. On hex socket shoulder screws the connection between the two is direct: the lower the head, the shallower the socket, and the shorter the length of flat the key can bear on.

That produces a specific trade. A low head lets a cover or a plate pass over the fixing without touching it, which is often why the part was chosen. But the socket that remains has less depth, and a key that only engages part way bears on a shorter run of each flat, so the corners take more load for the same torque. At the small sizes the difference is a fraction of a millimetre and it decides whether the joint can be serviced twice.

The shoulder side of the part is unaffected by the head height in principle and affected in practice. The shoulder is ground to a diameter and a roundness, and those are what the bore runs on; but the shoulder is measured from the underside of the head, so a head that is not square turns into a shoulder that runs slightly out of line with the axis. On a low head, where the bearing face is smaller, that effect is easier to miss.

Then there is the finish. Zinc plating protects by sacrificial action and suits dry joints, but it is a film on both the shoulder and the socket. On a shoulder that is meant to run in a bore, a plated layer is a wear surface rather than a bearing surface, and on a shallow socket it changes which key seats. That is why a plated shoulder screw is usually specified for a locating fit rather than for a running pivot.

The practical conclusion is that hex socket shoulder screws are a locating part with a low profile, not a high-torque pivot. Where a joint has to be tightened hard and turned often, the taller head with a deeper socket is the better basis, even if it means changing what passes over it.

Shoulder, Head and Socket

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

The shoulder fit is agreed against the bore rather than quoted as a diameter. On a locating part the pair of tolerances is the specification, and a shoulder that is a tenth under size in a bore that was machined to suit is a joint that moves where it was meant to hold.

Head height is the number that decides how much socket is available. It is worth stating on the drawing for that reason alone, because a customer who asks for a lower head is also asking for a shallower drive, and the two requests have to be reconciled before the part is made.

Socket depth is measured from the floor to the top face and proved with the key. On a low head this is the number to watch: a socket that is a few hundredths shallow will accept a key that only engages part way, and the corners will mark before the clamp is reached.

What Hex Socket Shoulder Screws Give and Costs

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

The value is a locating fixing that stays out of the way. Where a mechanism has a plate running over its fasteners, this is the part that lets the joint be located and clamped without the head becoming an obstruction.

The cost is the drive. A low head gives little socket, and on a plated part the film sits inside it, so the key fit and the torque have to be agreed rather than assumed.

Zinc Plate and the Alternatives

The recorded finish is zinc plated. On a shoulder screw that is a cost-driven choice: it protects by sacrificial action and it is uniform enough on a turned part, but it puts a film on the shoulder that was meant to be a bearing surface.

Surface Options for Hex Socket Shoulder Screws

Where the shoulder is a bearing surface rather than a locating one, a coating is the wrong answer and a post-plate grind or a bare surface is needed. Where the part simply locates a plate, a zinc plate is adequate and cheaper.

On a low head the socket is the feature the finish affects most, because the film changes which key seats. A plated part is proved with the production key after plating, and the depth is measured in the plated state.

Where Hex Socket Shoulder Screws Are Used

Three settings where the head has to stay low and the shoulder has to locate:

Why Shi Shi Tong for Hex Socket Shoulder Screws

Four reasons that matter on a part where the head height and the shoulder have to agree, each tied to something the drawing or the first article has to prove:

How Hex Socket Shoulder Screws Are Made

These screws are turned from bar stock, with the shoulder and the low head machined in the same setup, the hexagon cut, the shoulder ground to its diameter and the thread cut behind it; the parts are then zinc plated. The first piece of every run is measured on shoulder diameter and roundness, shoulder length, head diameter and height, socket size and depth, and thread.

Machining the shoulder and the head in one setup is what keeps them on the same axis. A low head has less material to hold in a second operation, so the temptation to machine it separately is real and the result is a shoulder that runs out of line with the head, which shows as a pivot that binds at one point of each revolution.

The hexagon is cut into the reduced head and the depth is set against the remaining height. On a low head that depth is the limiting feature: too shallow and the key does not reach the floor, too deep and the walls become thin enough to spread under torque.

Plating follows, and the socket is gauged again afterwards. A zinc film inside a shallow hexagon changes which key seats, so the part is proved with the production key in its plated state rather than in the white state.

Inspection: Shoulder, Head and Socket

What decides whether hex socket shoulder screws pass is the shoulder diameter and roundness, the shoulder length, the head height and the socket. The inspection agreement covers those, and the criteria come from the drawing.

Shoulder and socket on the projector	Thread and start checked
Core hardness checked	Salt-spray testing of the zinc layer

The shoulder is measured for diameter at several points and for roundness, and the length is taken from the head underside. Head height and socket depth are read together, because the socket lives in the reduced head and the two travel in opposite directions as the head gets lower.

The fit is proved functionally: a sample from every batch is fitted into a gauge bore of the customer’s size and checked for play by hand. On a locating part that is the check that turns two tolerances into a joint.

The socket is proved with the production key at the torque the joint calls for, and the corners are inspected under magnification. On a plated low head that cycle shows whether the film has changed which key seats.

Certificates and Material Documentation

Every batch is traceable to the bar stock 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 thickness is recorded for the batch.

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 shoulder and the socket, and the plating and RoHS reports. The documents carry the drawing revision and the batch number, so a repeat order of hex socket shoulder screws locates 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 a locating part the first article is fitted into the customer bore, because the fit is what the part exists for. 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 turning cell and the grinding setup 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

Hex Socket Screw Specification Table Socket size and head height against diameter, across the socket family. Read the guide

Products

Shoulder Screws The standard cap head shoulder screw in stainless. Shoulder Screws	Flat Head Shoulder Screws The flush shoulder screw in titanium. Flat Head Shoulder Screws	Low Profile Socket Head Screws A low head without a shoulder. Low Profile Socket Head Screws
Low Head Socket Head Cap Screws A reduced head in carbon steel. Low Head Socket Head Cap Screws	Stainless Shoulder Screws The stainless shoulder family with a slotted head. Stainless Shoulder Screws	Socket Head Cap Screw The standard cap head for comparison. Socket Head Cap Screw

Hex Socket Shoulder Screw FAQ

Order Hex Socket Shoulder Screws

How a low 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.