M8 Shoulder Screw, Custom Screw Factory

We make M8 shoulder screws in carbon steel with a blue zinc plate, a truss head with a cross recess and a hexagon collar under the head, quoted to the drawing. The wide head spreads the clamp on a thin panel, the shank sets the position, and the plated shank is checked where it has to locate.

Watch the factory video·Email sst@szsst88.com

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 M8 Shoulder Screws Are

An M8 shoulder screw has an 8 mm thread with a ground shank in front of it that locates the part and stops the thread at a fixed depth. The part recorded here is carbon steel with a blue zinc plate, quoted with a truss head and a cross recess, and the shoulder made to the drawing.

Ground shank. A precision diameter that passes through the panel or bracket and carries the load.

Truss head. A wide, shallow head that spreads the clamp over a large annulus.

Hex under the head. A hexagon collar between the head and the shank that gives a second drive point.

They are used where a thin panel has to be held without dishing, and where the screw also positions what it holds.

The wide head is what makes the M8 size practical: at 8 mm diameter, the thread can pull hard enough to dish a light panel, so the head area has to grow faster than the load.

Two Ways to Drive, One Surface to Bear On

This screw can be turned from two places. The cross in the top of the truss head takes a driver from above, and the hexagon collar under the head takes a wrench from the side. In a panel joint where the top is visible and the side is open, that means the part can be driven the way the assembly station is arranged rather than the way the screw was designed.

The two drive points do different jobs. The cross is the assembly drive: quick, one-handed, and the one that is used on the line. The hex is the controlled drive: a wrench gives more torque for the same hand effort and does not depend on a bit that may be worn. When a joint has to be tightened past what a cross recess can take, the hex is what makes it possible without a different screw.

The collar is also a bearing surface. It sits under the head as a flat annulus, and on a joint where the head is over a slot or a recessed panel, that annulus is what actually contacts the part. Its diameter determines the clamp area as much as the head does.

Behind the collar the shank is plain, and this is the locating length. The thread starts after it, so the joint stack above the thread is what the shank passes through, and the thread does not touch the panel at all. That separation is what keeps a truss head joint from deforming the hole it goes through.

The order of these features is the thing to read on a drawing: head, collar, shank, thread. Get the collar height or the shank length wrong and the same fasteners will either stand proud or pull through.

Head, Collar, Shank and Thread

The part is quoted to the drawing, with the head diameter, the collar across flats, the shank diameter and length and the thread stated separately. Custom lengths up to 2,000 mm, subject to DFM review after drawing submission. The quotation for M8 shoulder screws carries all four, because on a truss head joint they work as a set.

The head diameter is the dimension that decides the joint. A truss head is chosen for a light panel, and the panel is held because the clamp is spread over a wide annulus; a head that is even a few millimetres smaller can be the difference between a panel that stays flat and one that dishes around the screw.

The collar height is the second one, because it sets the height of everything above the panel. On a recessed panel the collar disappears into the recess; on a flat panel it stands above the surface by its full height.

M8 shoulder screws with a collar and a ground shank are quoted as a set, and the shank is agreed against the hole, as on any locating part. The shank diameter and the panel hole form the fit together, and the shank length is the thickness the joint can clamp above the thread.

What M8 Shoulder Screws Give and Costs

Four properties decide these M8 shoulder screws, and each one carries a cost:

The value is a panel joint that stays flat. A truss head spreads the load, so the panel does not dish, and the shank sets the position so the panel does not slide; both are done without a washer, which removes a part and a step from the assembly.

The cost is visual and dimensional. The head is large and it is on the outside of the product, so it is chosen partly for appearance, and the plate has to be uniform because it is seen. And the blue zinc layer is thicker than clear zinc, which is a change on the shank if it is plated after grinding.

Blue Zinc and the Ground Shank

The recorded finish is blue galvanized, a colour zinc plate. It gives a brighter, slightly blue-white appearance than clear zinc and it is a thicker sacrificial layer, which suits appliance and enclosure parts that are seen and handled.

Surface Options for M8 Shoulder Screws

On M8 shoulder screws with a locating shank, the plate is a dimension before it is a finish. The blue zinc layer is applied after grinding, so it adds its thickness to the shank diameter; if the joint needs the ground size to hold, the shank is either masked or re-checked in the plated state.

The head is the visible side, so the plate is judged on coverage: a truss head has a large flat face and a rounded edge, and coverage on the edge is what decides whether the part looks uniform across a batch.

Where M8 Shoulder Screws Are Used

Three assemblies where a wide head and a locating shank are both needed:

Why Shi Shi Tong for M8 Shoulder Screws

Four reasons that matter when a visible head sits over a locating shank, each tied to something the drawing or the first article proves:

How M8 Shoulder Screws Are Made

These screws are turned from steel bar in a single setup, with the truss head formed, the hexagon collar milled, the shank turned and then ground, the cross cut into the head and the thread cut; the parts are then blue zinc plated. The first piece of every run is measured on head diameter, collar across flats, shank diameter and length, cross depth and thread.

Milling the hexagon collar under the head is the operation that sets the second drive point on every batch of M8 shoulder screws. The flats have to be cut square to the shank, because a wrench on an out-of-square collar both loses grip and tilts the screw in the panel; the collar height also has to be right, since it is a bearing surface that sits between the head and the panel.

The truss head is formed before the cross is cut, so the cross depth is taken from a finished head face rather than from a rough one. On a wide flat head the face is the visible surface, and any tool mark from the cross cut is seen across the whole panel.

Grinding the shank before plating is what makes the locating diameter; plating after grinding adds to it, so the drawing states whether the shank size applies before or after the plate. Where the joint is tight, the shank is masked during plating to keep the ground size.

Inspection: Head, Collar and Shank

What decides whether M8 shoulder screws pass is the head, the collar, the shank and the plate. The inspection agreement covers those, and the criteria come from the drawing.

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

The shank is measured for diameter and length, and for roundness where the joint depends on it. On a plated part the measurement is taken after plating as well, because the layer is applied after grinding and the delivered size is the one that matters.

The collar is checked across flats and for squareness to the shank. The head is checked for diameter, height and flatness of the bearing face, and the cross for depth and width.

The plate is checked for appearance and for coverage on the head edge, and a sample from each lot goes into the salt-spray chamber. Blue zinc is a sacrificial layer, so the test is about how the layer behaves at the head edge and on the thread rather than on the flat face.

Certificates and Material Documentation

Every batch of M8 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 shank and collar, and the plating report. The records carry the drawing revision and the batch number, so a repeat order of M8 shoulder screws matches the first article.

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 panel part the first article is assembled onto the customer panel, because a proud head or a dished panel only shows in the joint. Buyers visit during the process to review samples.

For M8 shoulder screws the visit usually includes a look at the plated sample, because the finish is part of the specification. 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 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 Are Truss Head Screws Where a wide, shallow head is the right choice, and how it is customised. Read the guide

Are Zinc Coated Screws Magnetic What a zinc layer does to the part underneath, and what it does not change. Read the guide

Products

Brass Shoulder Screws The brass cap head shoulder version. Brass Shoulder Screws	Shoulder Thumb Screws A knurled thumb head with a shoulder in 303. Shoulder Thumb Screws	Alloy Steel Shoulder Screws The non standard alloy steel shoulder version. Alloy Steel Shoulder Screws
Flat Head Shoulder Screws The countersunk shoulder version. Flat Head Shoulder Screws	Truss Head Shoulder Screws The truss head version in stainless steel. Truss Head Shoulder Screws	M4 Shoulder Screws The long shoulder version in stainless. M4 Shoulder Screws

M8 Shoulder Screw FAQ

Order M8 Shoulder Screws

How an M8 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.