Product and application brief
Shoulder bolts, also called shoulder screws, combine a head, a defined smooth shoulder and a smaller threaded end. The shoulder is the distinguishing feature of this page. These parts are specified where an assembly requires a controlled unthreaded section rather than threads along the working length. A socket-head screw without a defined shoulder belongs to a different product brief.
Product forms and reference names
| Product form / field | Reference and distinguishing details |
|---|---|
| Metric hexagon-socket shoulder screws | ISO 7379:1983 identifies this metric construction; ISO describes nominal shoulder diameters from 6.5 to 25 mm. Use the selected standard dimensions, not an assumed catalogue substitution. |
| Catalogue shoulder variants | Maker catalogues may use ISO-related family names while declaring dimensional deviations. Ganter notes differences including 6 versus 6.5 mm, 12 versus 13 mm and 24 versus 25 mm shoulders. |
| Inch-dimension shoulder parts | State shoulder diameter and length in inches together with the exact thread. This is an inch specification option, not an asserted equivalent to ISO 7379. |
| Drawing-based precision shoulders | Define the shoulder, transition reliefs, head and thread independently, including required dimensional and geometric tolerances. |
Read the model number by dimension
In Ganter’s catalogue example 7379-10-M8-35, the 10 identifies the shoulder diameter, M8 the end thread and 35 the shoulder length, in millimetres. It is a manufacturer reference for identifying geometry, not a FastenerBridge SKU or a brand-affiliation claim. An M8 thread alone does not describe a 10 mm shoulder.
Standard and catalogue dimensions are not identical by default
The official ISO scope and an ISO-labelled commercial series must be distinguished. Ganter explicitly identifies deviations and sizes outside the official sheet. Do not assume a 6 mm catalogue shoulder is the same part as a 6.5 mm standard shoulder. Match the shoulder diameter, length, thread and selected tolerance against the controlled specification.
Keep the shoulder fit explicit
Specify the required shoulder-diameter tolerance, length tolerance and surface requirements. Where the design controls concentricity, runout or relief geometry, include those requirements on the drawing. The appearance image cannot establish a tolerance, bearing fit, load rating or inspection result.
Specification fields
| Product form / field | Reference and distinguishing details |
|---|---|
| Product reference | ISO edition if applicable, exact manufacturer model used as a reference, or customer drawing revision. |
| Shoulder diameter | Specify separately from the smaller thread diameter; include required tolerance. |
| Shoulder length | Define the shoulder-end and head-bearing datums; do not substitute overall screw length. |
| End thread | Diameter, pitch or TPI, thread series and threaded-end length. |
| Head and drive | Head diameter and height, hexagon socket dimensions, and any knurl requirement. |
| Transitions | Relief diameters and lengths, fillets and geometric requirements where controlled by the design. |
| Material and surface | Required material, mechanical properties, coating and shoulder surface finish; do not infer these from an image. |
| Quantity | Quantity with units for each shoulder/thread/length combination. |
Common product questions
Are shoulder diameter and thread diameter the same?
No. A shoulder screw normally has a larger smooth shoulder and a smaller threaded end. Specify both dimensions.
Does every catalogue ISO 7379 part match the official ISO dimensions?
No. Some catalogues expressly list departures and additional sizes. Use the declared dimensions and the selected specification.
What does the length on a shoulder screw refer to?
Identify the shoulder length separately from the thread length and overall length. Show the measurement datums on the selected drawing.
Related bolt types
Product references
References checked 6 October 2026 explain product identity. Third-party model names and approvals are not FastenerBridge brand affiliation, stock or certification claims. Final geometry and requirements follow the selected specification.