What is a shoulder screw used for?

Shoulder screws (also called stripper bolts or shoulder bolts) are used as precision pivot pins, axles, guide pins, and spring perches. The precision-ground shoulder acts as a bearing surface while the threaded end clamps into the tapped hole. Common applications include die sets, jigs, linkages, and rotating components.

What bore hole size should I drill for a shoulder screw?

The bore hole diameter depends on the fit class. For a close fit (pivot/bearing): bore = shoulder diameter + 0.010 to 0.025 mm. For a normal fit (sliding): bore = shoulder diameter + 0.025 to 0.075 mm. For a loose fit (guide): bore = shoulder diameter + 0.075 to 0.150 mm. The calculator gives exact bore sizes based on ISO 7379 tolerances.

What thread size does a metric shoulder screw use?

Per ISO 7379, the thread diameter is always smaller than the shoulder diameter. For example, a 6 mm shoulder uses an M5 thread, an 8 mm shoulder uses M6, a 10 mm shoulder uses M8, and a 12 mm shoulder uses M10. This ensures the shoulder is the load-bearing surface.

What is the difference between a shoulder screw and a cap screw?

A cap screw is fully or partially threaded and clamps two or more parts together by thread tension. A shoulder screw has a precision-ground unthreaded shank (the shoulder) that acts as a bearing or pivot surface — only the short threaded tip anchors it. They serve completely different mechanical functions.

What standard covers metric shoulder screws?

Metric shoulder screws are covered by ISO 7379 (hexagon socket head shoulder screws) and the equivalent German standard DIN 9841. These define shoulder diameter, shoulder length, thread size, thread length, head diameter, head height, and hex key size.

Metric Shoulder Screw Calculator – Stripper Bolt Dimensions M4–M20 | CalcEngines

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Shoulder Screw Calculator

Full ISO 7379 / DIN 9841 dimensions — shoulder diameter, shoulder length, bore fit tolerances, thread specs, and head dimensions for 4 mm to 20 mm shoulder diameter.

ISO 7379 / DIN 9841 4 mm – 20 mm shoulder Bore fit calculator mm / inch toggle Free to use

Parameters

Shoulder Diameter (d2) Precision ground shank diameter

Shoulder Length (l2) Length of the unthreaded shoulder

Bore Fit Class

Select fit class below ↓

Bore Fit Class

inch

Key Dimensions

Select a shoulder diameter and length above, then click Calculate.

Dimension Breakdown by Zone

Bore Hole Size (Normal fit selected)

⚠ Bore tolerance is critical: The shoulder must be a precision fit in the bore — it is the load-bearing surface. Drill and ream (do not just drill) for close and normal fits. A reamer matched to the bore size gives the best results.

Thread & Tapped Hole

Full Reference Chart (ISO 7379 — normal bore fit)

Shoulder Ø d2	Thread d1	Thread Pitch	Thread Length b	Head Ø dk	Head H k	Hex Key s	Tap Drill	Bore (Normal)	Bore (Close)	Bore (Loose)

Common Questions

What is a shoulder screw (stripper bolt) used for? +

Shoulder screws act as precision pivot pins, axles, guide pins, and spring perches. The precision-ground shoulder is the functional part — it provides the bearing surface. The threaded end simply anchors the screw. Common uses include stamping die sets, jigs and fixtures, linkages, cam followers, and spring-loaded mechanisms.

What bore hole size should I use for a shoulder screw? +

It depends on your application. Close fit (+0.010 to +0.025 mm over shoulder diameter) is for precision pivots and bearings. Normal fit (+0.025 to +0.075 mm) is for general sliding and die set applications. Loose fit (+0.075 to +0.150 mm) is for guides and easy assembly. Always drill and ream — do not just drill — for close and normal fits.

Why is the thread diameter smaller than the shoulder diameter? +

This is intentional per ISO 7379. The shoulder diameter is always larger than the thread so that the shoulder — not the thread — is the load-bearing surface. It also allows the shoulder to seat flush against the mating part without the threads interfering. For example, a 10 mm shoulder uses an M8 thread.

Should I drill or ream the bore for a shoulder screw? +

For close and normal fits you must ream — drilling alone does not achieve the required surface finish or tolerance. Drill slightly undersize (typically 0.1–0.2 mm under bore size), then ream to the final bore diameter. For loose fits, careful drilling may suffice but reaming always gives better results.

What is the difference between ISO 7379 and DIN 9841? +

ISO 7379 is the international standard and DIN 9841 is the German standard for hexagon socket head shoulder screws. They are dimensionally equivalent — a DIN 9841 screw meets ISO 7379. The key dimensions (shoulder diameter, thread size, head dimensions) are identical between the two standards.