M6 Socket Head Cap Screw Dimensions Selection Guide | Hebei Wotu Fastener Manufacturing Co., Ltd.
An M6 socket head cap screw is usually chosen where a compact cylindrical head, a hex socket drive and higher clamping strength are needed in machinery, fixtures, tooling, frames or equipment assemblies. The key purchase decision is not only “M6,” but the standard, length, thread pitch, material grade and finish that match the mating part.
For a standard metric M6 socket head cap screw made to ISO 4762 or the similar DIN 912 style, buyers commonly expect a 6 mm nominal thread diameter, 1.0 mm coarse thread pitch, 10 mm head diameter, 6 mm head height and a 5 mm hex socket. Always confirm the drawing or standard version before ordering, because small differences affect counterbores, wrench fit and assembly clearance.
Brand: Hengzuan Surface: blue and white zinc plated, optional color zinc plated, black oxide treatment Specifications: in stock ST3.5/ST4.2/ST4.8 mainstream specifications, rod length 16~50mm full size range, supports nonstandard length customization, suitable for drilling steel sheets 2~5mm Packaging: 25kg cartons, full pallets packed on wooden pallets, support neutral packaging, private-label customization
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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: blue and white zinc plated Specifications: in stock 3.5/3.9/4.2 mainstream wire diameter, rod length 16mm~80mm full size range in stock, supports nonstandard length customization; fine/coarse tooth types are available Packaging: 25kg export cartons, full pallets wrapped with film, supports neutral export 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
Read MoreDimension and fit guide
Relevant selection criteria for M6 socket head cap screws include the governing standard, thread pitch, under-head length, head diameter, head height, socket size, material, strength class, coating and tolerance needs. These details determine whether the screw fits the counterbore, drives cleanly with the correct hex key and gives the intended clamping performance.
| Criterion | What To Check | Why It Matters | Buyer Tip |
|---|---|---|---|
| Nominal thread diameter and thread pitch | Confirm the screw is M6 and record the pitch, rather than relying on the M6 label alone. | Pitch affects nut or tapped-hole compatibility, thread engagement and interchangeability. | Ask: “Which pitch is supplied, and can you provide the thread specification on the drawing or order confirmation?” |
| Specified screw length and measurement method | Check the required length and whether it is measured from beneath the head or by another stated convention. | Socket head cap screws are normally selected by usable threaded length; an unclear method can produce the wrong fit. | Ask: “Please confirm the available length range and show the length datum on the dimensional drawing.” |
| Head diameter and head height | Compare the head dimensions with the available counterbore, recess or surrounding clearance. | The screw may have the correct thread yet fail to seat, interfere with adjacent parts or sit too high. | Ask: “What head diameter and height apply to this M6 version, and which dimensional standard is being followed?” |
| Hex socket size and drive depth | Verify the internal hex size and the socket depth against the intended installation tool and access space. | A mismatched key or shallow drive can prevent full engagement and increase the risk of damaging the socket during tightening. | Ask: “What hex socket dimensions are specified, and can you share a drawing or inspection record for the production lot?” |
| Dimensional standard and tolerances | Identify the governing standard and review tolerances for thread, length, head and socket dimensions. | Two screws marked M6 can differ in fit if their standards or allowable dimensional variation differ. | Ask: “Which standard controls these dimensions, and can you provide the tolerance table with the quotation?” |
The most common confusion is between the screw’s nominal size and its overall dimensions. “M6” describes the thread diameter, not the head diameter or screw length. The length is normally measured from under the head to the end of the screw, so an M6 × 20 socket head cap screw has about 20 mm of length below the head, not including the head height.
Thread pitch also matters. M6 coarse thread is commonly 1.0 mm pitch, while fine-thread versions use a smaller pitch for different engagement and adjustment requirements. Coarse thread is easier to source and more forgiving in general assembly; fine thread can offer finer adjustment and better resistance to loosening in some designs, but it must match the tapped hole exactly.
Start with the standard and drawing callout. If the mating part has a counterbore, the head diameter and head height must match the design allowance. A screw that is correct in thread size but built to a different head style may sit proud, bottom out, or leave too little clearance for the hex key.
Check length against thread engagement and stack thickness. Too short may not provide enough engagement in the tapped material; too long can bottom out in a blind hole or interfere with moving parts. For assemblies with washers, spacers or coatings, include those thicknesses in the length decision.
Select material, strength class and surface finish for the working environment. Carbon steel alloy socket cap screws are common in mechanical assemblies, but stainless steel or coated fasteners may be preferred where corrosion resistance or appearance matters. Do not assume two screws with the same M6 dimensions have the same strength or finish.
Avoid ordering from only a short description such as “M6 socket screw.” Send the required standard, size format, length, pitch, material grade, finish, quantity and any packaging needs. If the screw will fit an existing counterbore or a critical tapped hole, include a drawing or sample reference so the dimensions can be checked before production or shipment.
| Criteria | Importance | Description | Example Options |
|---|---|---|---|
| Thread pitch | Critical because the screw must match the tapped hole exactly. | Coarse and fine M6 threads have different pitches and cannot be treated as interchangeable. Pitch also affects thread engagement and adjustment characteristics. | An M6 coarse thread is commonly specified as 1.0 mm pitch; a fine-thread request should state its exact pitch. |
| Under-head length | Critical for achieving engagement without bottoming out or creating interference. | Length is measured from beneath the head to the screw tip. Select it against the joint thickness, spacers, washers and available blind-hole depth. | M6 × 20 indicates about 20 mm of length below the head, not including head height. |
| Head and socket dimensions | Critical where the screw sits in a counterbore or has limited tool clearance. | Head diameter, head height and hex socket size determine whether the fastener seats correctly and can be driven with the available key. | For a common ISO 4762 or DIN 912-style reference, buyers may check a 10 mm head diameter, 6 mm head height and 5 mm socket against the drawing. |
| Material, strength class and finish | Important because identical dimensions do not guarantee the same mechanical or environmental performance. | Choose these properties according to load, exposure, corrosion concerns and appearance requirements. A stainless, coated or carbon-steel option may involve different trade-offs. | A dry indoor fixture and an assembly exposed to moisture may require different material or finish requirements even when both use M6 dimensions. |
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M6 identifies the screw's nominal metric thread diameter, approximately 6 mm. It does not specify the head diameter, head height, socket size, overall length, material or finish.
No. The screw must also match the counterbore's available diameter and depth, along with the hex socket clearance needed for the tool. Confirm the governing standard or compare the screw drawing with the assembly drawing before ordering.
M6 coarse thread is commonly 1.0 mm pitch and is a practical choice for general assemblies when the tapped hole is designed for it. Fine thread can suit applications needing finer adjustment or a different engagement arrangement, but it is not interchangeable with a coarse-threaded hole.
A washer changes the clamped stack and may help in some through-hole joints, but it does not solve a screw that bottoms out in a blind hole or interferes with another component. Check the available thread depth, joint thickness and required engagement before selecting a washer or changing length.
State the standard or drawing reference, size and under-head length such as M6 × 20, thread pitch, material or strength class, surface finish, quantity and packaging requirement. Add the counterbore or tapped-hole details if dimensional fit is critical, and ask the supplier to confirm the relevant dimensions before production.
Send the required standard or drawing, size and length such as M6 × 20, thread pitch, material or strength class, finish, and order quantity so the screw dimensions and fit can be checked.
