Allen Head Fasteners | Hebei Wotu Fastener Manufacturing Co., Ltd.
Allen head fasteners use an internal hexagonal drive, so the tool engages inside the head rather than around its outside. That makes them useful where a clean profile, controlled tightening, or access in a narrow assembly matters.
The main purchase decision is not the drive alone. Confirm the head style, thread and length, material or coating, and the mating tool before selecting an allen-head screw for machinery, fixtures, furniture or general assembly.
Brand: Hengzuan Surface: high temperature black phosphated anti-rust treatment, blue zinc, color zinc plated coating can be replaced as needed Specifications: in stock ST3.5/ST4.2/ST4.8 common specifications, rod length 16mm~50mm, complete, supports nonstandard size customization, suitable for drilling steel sheets 2~5mm Packaging: 25kg cartons, whole wooden pallets, support neutral packaging, private-label customization
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Brand: Hengzuan Surface: Color zinc plated, optional blue-white zinc plated, black oxide treatment Specifications: Chinese national standard ST4.2/ST4.8/ST5.5 specifications, rod length 13~50mm in stock, supports nonstandard length customization Packaging: 25kg export cartons, full wooden pallets wrapped with film, supports neutral packaging, private-label customization
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Brand: Hengzuan Surface: blue and white zinc plated, can be customized color zinc plated, black oxide plated Specifications: Comply with GB/T15856.2-2002 Chinese national standard, in stock ST4.2/ST4.8/ST5.5 full range of specifications, length 13mm~75mm optional, supports customized nonstandard rod lengths; drilling adaptation plate thickness 0.7~6mm Packaging: 25kg export cartons, full pallets wrapped with film, supports neutral export packaging, customer private-label customization
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Brand: Hengzuan Surface: blue and white zinc plated, can be customized color zinc plated, black oxide plated Specifications: in stock 3.5/3.9/4.2/4.8/5.5 mainstream wire diameter, rod length 13mm~75mm full size range, nonstandard length can be customized as needed Packaging: 25kg export cartons, full wooden pallets wrapped with film, supports neutral export packaging, private-label customization
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Brand: Hengzuan Surface: color zinc plated, customized blue-white zinc plated, black oxide Specifications: in stock 3.9/4.2/4.8/5.5 full diameter, length 13mm~75mm full size range, supports customized nonstandard rod lengths Packaging: 25kg export cartons, full pallets wrapped with film, supports neutral export packaging, customer private-label customization
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Brand: Hengzuan Surface: blue and white zinc plated, can be customized color zinc plated, black oxide plated Specifications: Comply with GB/T15856.2 Chinese national standard, in stock ST3.5/ST4.2/ST4.8/ST5.5 mainstream wire diameter, rod length 13mm~50mm full range of specifications, nonstandard length customization on demand, drilling applicable plate thickness 2~5mm Packaging: 25kg export cartons, full pallets wrapped with film, supports neutral export packaging, private-label customization
Read MoreAllen-head selection criteria
Compare allen-head options by head geometry, internal hex size, thread specification, length, material, finish and dimensional standard. The correct choice depends on the joint design and installation access, not simply on the presence of a hexagonal recess.
| Criterion | What To Check | Why It Matters | Buyer Tip |
|---|---|---|---|
| Allen drive size and fit | Match the internal hex socket to the intended wrench or bit and inspect a sample for full engagement. | A poor fit can round the socket, interrupt installation and make later removal difficult. | Can you provide the socket size and a sample for a fit check with our installation tool? |
| Head diameter and height | Compare the head dimensions with the available recess, clearance and required bearing area in the assembly. | A head that is too large may interfere with adjacent parts, while one that is too small may not clamp securely. | Please confirm the head dimensions and whether the fastener must sit flush, recessed or proud of the surface. |
| Thread size, length and form | Specify the mating material, thread size, usable length and whether the screw is for a pre-tapped hole or a self-forming application. | Thread engagement affects holding strength, installation effort and the risk of bottoming out or damaging the assembly. | What material and hole condition will the Allen-head fastener enter, and how much thread engagement is required? |
| Material and surface finish | Review the stated base material and coating or finish against moisture, chemicals, temperature and contact with dissimilar metals. | The finish and material influence corrosion resistance, appearance and compatibility with the surrounding assembly. | Which exposure conditions should the material and finish withstand, and is a particular finish required for the application? |
| Installation torque and access | Confirm the tightening method, tool access and any torque or clamping requirements for the joint. | Allen-head fasteners suit limited-access assemblies, but excessive or uneven tightening can damage the socket or joint. | What tool access and tightening procedure will your assembly line or maintenance team use? |
“Allen head” usually describes the internal hex drive, while the head shape may be socket cap, button, flat countersunk or another form. A socket head cap screw gives more head height for a larger internal drive and stronger clamping applications; a button head offers a lower, rounded profile; a countersunk head is intended to sit flush in a prepared hole.
This distinction affects clearance, seating, tool access and load transfer. A flush-fit screw may be unsuitable for a plain drilled hole, while a taller socket head may interfere with a moving part or cover. Specify both the drive type and the head geometry rather than ordering by “allen head” alone.
Match the head to the joint. Check the available clearance above and around the fastener, the required seating surface and the access angle for the hex key or bit. For recessed joints, confirm the counterbore or countersink form; for exposed surfaces, consider whether a rounded button head or a taller socket head better suits the assembly.
Specify the thread and engagement. State the thread system, diameter, pitch where applicable, overall length and whether the joint uses a nut, threaded insert or tapped hole. A screw that is too short may not develop adequate engagement, while excessive length can bottom out or project into a moving or finished area.
Choose material and finish for the environment. Corrosion exposure, appearance, temperature and contact with dissimilar metals can change the suitable material or coating. Confirm the required strength class or material grade, finish, colour and any restrictions on coating thickness before approval. Do not assume a surface finish provides the same protection in every application.
Check the drive before placing the order. Ask for the internal hex size, dimensional standard, thread tolerance and inspection information relevant to the assembly. For an enquiry, send a drawing or clear dimensions together with the quantity, application, required head style, material or finish and destination so the proposed part can be checked against the joint.
| Criteria | Importance | Description | Example Options |
|---|---|---|---|
| Head geometry | Critical when clearance, seating or surface appearance affects the assembly | Compare socket cap, button, countersunk and other internal-hex head forms by their height, width and seating requirements. | A countersunk form suits a prepared flush seat, while a button head may suit an exposed surface with limited height. |
| Drive access | Critical for installation and future service | Check whether a hex key or bit can approach the recess straight enough to engage fully, and confirm clearance around the tool. | A recessed fixture may have enough room for a top-entry hex key but not enough side clearance for an external wrench. |
| Thread and engagement | Critical to the joint fit and usable length | Match the thread system, diameter, pitch where applicable and length to the tapped hole, nut or threaded insert. Avoid lengths that bottom out or project into moving areas. | A screw for a threaded insert may require a different usable length from one passing through a plate into a tapped body. |
| Material and finish | Important where corrosion, appearance, temperature or mixed-metal contact matters | Select the material or coating for the operating environment and confirm that the finish, colour and coating thickness are acceptable for the joint. | An indoor furniture assembly and an exposed machine assembly may need different finish considerations even when their head shape is similar. |
| Dimensional standard and inspection information | Important for repeat orders, interchangeable parts and quality approval | Confirm the applicable dimensional standard, internal hex size, thread tolerance and inspection documents required by the assembly or purchasing process. | A repeat production order may need the same head dimensions and drive size as an approved drawing rather than only a nominal diameter and length. |
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They can suit assemblies with limited side clearance because the tool engages in the top of the head rather than around its outside. The installer still needs enough vertical access and a clear path for the hex key or bit, so check the access angle and surrounding features before selecting the part.
Choose a socket cap when head height and a deeper drive are acceptable, a button head when a lower rounded profile is preferred, and a countersunk version when the joint is designed for a flush surface. These shapes are not interchangeable without checking the mating hole, clearance and required seating area.
No. It normally identifies the internal hexagonal drive, not the head geometry, thread, length, material or finish. A complete enquiry should name the head style and the dimensions needed to match the joint.
Only if the available tool access, head clearance and joint design support the change. An external-hex fastener is tightened around the head, while an internal-hex design needs a correctly sized tool to enter the recess; changing between them may require different clearance or installation equipment.
Provide a drawing or clear dimensions, head style, thread system and size, pitch where applicable, length, material or finish, quantity and application. Also state the mating hole or insert and any required dimensional standard or inspection information so the proposed part can be checked for fit.
Please provide the required head style, thread and length, plus the material or finish and application. A drawing or hole dimensions can also help us review fit and tool access.
