Socket Head Cap Screw Dimensions Chart — Metric & Inch

Socket-head cap screw dimension lookup

Use the table to compare the body diameter, head diameter, head height, socket size, and minimum key engagement for the listed metric and inch socket-head cap screw sizes. Search for M6, M10, 1/4-20, or 3/8-16. The table keeps the metric and inch systems separate and identifies the governing standard family for each row.

“Maximum” and “minimum” describe the dimensional limits shown by the bounded manufacturer cross-checks. The socket size is the nominal internal hex size. Minimum key engagement is the minimum axial engagement dimension in the source table. These values help with preliminary modeling and tool access; they do not replace the applicable standard or a supplier’s controlled drawing.

What the dimensions mean

Basic screw diameter identifies the nominal thread diameter. The pitch is shown with the row, such as 1.0 mm for M6 × 1.0 or 20 threads per inch for 1/4-20. The basic diameter is not the same as the measured minor diameter or the maximum body diameter.

Body diameter describes the cylindrical shank limit used by the source table. A threaded portion can have a different measured diameter because thread geometry, tolerance class, coating, and measurement location affect the result.

Head diameter controls the radial envelope of the cylindrical head. It matters when you design a counterbore, a pocket, a washer seat, a clamp, or a nearby-wall clearance. Use the maximum value for conservative early layout. Add the required manufacturing and assembly clearance separately; this chart does not define a universal counterbore allowance.

Head height controls the axial envelope of the standard cylindrical head. It matters when a screw must sit below a surface, clear a cover, or remain accessible to a hex key. A counterbore depth is a separate design value. Do not assume that head height alone establishes a finished recess depth.

Socket size identifies the nominal hex key size for the listed socket-head cap screw family. Keep metric keys and inch keys separate. A nearby size can appear to fit and still damage the socket when torque is applied.

How to use the chart in a design

1. Read the complete fastener designation from the part, drawing, or purchase record.
2. Confirm that the fastener is a standard cylindrical socket-head cap screw in the ISO 4762 or ASME B18.3 family.
3. Use the maximum head diameter and height for the first clearance envelope.
4. Set the clearance hole, counterbore, wall distance, tool access, and tolerances from the assembly requirement.
5. Check the exact supplier drawing or licensed standard before production release.

The chart is useful for a first SOLIDWORKS layout, but a CAD feature does not decide which fastener family or standard applies. If you are modeling a recessed socket-head screw, compare these dimensions with the separate counterbore size chart and the selected clearance class in the clearance hole size chart.

Standard socket-head cap screws versus other socket screws

This lookup is limited to the standard cylindrical socket-head cap screw family. It does not cover button-head socket screws, low-head or reduced-head screws, countersunk socket screws, shoulder screws, set screws, spline-drive screws, Torx-drive screws, or security socket screws. Those families change the head envelope, socket geometry, or both. Select the exact head style before using a dimension in a drawing.

In particular, do not use a button-head or low-head value to size a standard counterbore. A smaller head can make a recess appear to fit while changing the bearing surface, tool access, head strength, and available engagement. If the supplier labels the part “button,” “low head,” “reduced head,” or another special style, stop and use that product family’s controlled data.

Metric and inch values

Metric rows use millimeters as the sourced basis. Inch display values are conversions using 25.4 millimeters per inch. Inch rows use the inch values from the source table as the sourced basis, and their millimeter display values are conversions using the same exact factor. Converted values are labeled in the underlying dataset so they are not mistaken for independent standard measurements.

Do not round a converted value into a new design limit. Keep the source-unit value visible on the drawing or purchasing record, then apply the tolerance and fit required by the selected standard and process.

Sources and limitations

The metric scope follows ISO 4762:2004. The inch scope follows ASME B18.3-2026. Fastenal and Fabory manufacturer data cross-check the metric ISO 4762 family. The STANLEY Camcar technical manual and catalog cross-check the inch socket-head cap screw family.

The complete ISO and ASME standards are licensed. Their public record pages establish the standard identity, scope, and edition, but they do not expose every dimensional row. This bounded chart was implemented without waiting for licensed PDFs. Verify the exact row, revision, material, coating, tolerance, and supplier drawing for production-critical work.

Frequently asked questions

What are the dimensions of an M6 socket-head cap screw?

In this bounded ISO 4762 lookup, the M6 row shows a 6.00 mm basic diameter, 10.22 mm maximum head diameter, 6.00 mm maximum head height, 5 mm socket, and 3 mm minimum key engagement. Confirm the exact product and standard before production use.

What socket size fits a 1/4-20 socket-head cap screw?

The bounded ASME B18.3 row uses a 3/16 in nominal hex socket and shows 0.120 in minimum key engagement. That applies to the standard cylindrical socket-head cap screw row, not to button-head, low-head, or set-screw variants.

Are socket-head cap screw dimensions the same as button-head dimensions?

No. Button-head screws have a different head shape and can have different head diameter, height, and socket dimensions. Use the exact product family and controlled source.

Can I use the chart as a final manufacturing specification?

No. Use it as a bounded reference and preliminary design aid. Check the licensed standard or the supplier’s controlled drawing for the selected size, material, coating, tolerance, and application.