Metric Socket Head Cap Screws (ISO/DIN)

CE Style

Inputs

Added to head Ø for pocketing (machining allowance).

Key Sizes

Fit & Machining Helpers

Data follows common ISO 4762/DIN 912 practice. For ASME B18.3.1M metric series, minor tolerances may differ—check supplier datasheets for safety-critical fits.

How to use this calculator

Boost Guide

Quick start

  1. Select Nominal size (e.g., M3, M6, M8).
  2. Pick the Thread pitch (coarse/fine as available).
  3. Optionally set a Counterbore margin (machining allowance).
  4. Click Calculate to see head dimensions, hex key, clearance holes, counterbore, and tap drill.
Uses common ISO 4762 / DIN 912 nominal values; small tolerances may vary by supplier.

Inputs

  • Nominal size: Metric thread (M3, M6, …).
  • Thread pitch P: Coarse by default; fine pitches shown where standard (e.g., M8 has 1.25 & 1.00).
  • Counterbore margin: Added to head Ø when pocketing; default +0.30 mm.

Results

  • Head Ø (dk), Head height (k): Nominal SHCS head dimensions.
  • Hex key (s): Across-flats size for the internal hex.
  • Clearance holes: Close, normal, and large recommendations (ISO 273 style).
  • Counterbore Ø and depth: Suggested pocket size = dk + margin, depth ≈ k + 0.5.
  • Tap drill (≈ d − P): Rule of thumb for ~70–75% thread engagement.

Examples

  • M6 × 1.0: dk ≈ 10.00 mm, k ≈ 6.00 mm, s = 5 mm; tap ≈ 6 − 1.0 = 5.0 mm; normal clearance ≈ 6.6 mm; counterbore Ø ≈ 10.3 mm.
  • M8 × 1.25: dk ≈ 13.00 mm, k ≈ 8.00 mm, s = 6 mm; tap ≈ 6.75 mm; normal clearance ≈ 9.0 mm.

Notes & limits

  • Dimensions are nominal; verify against supplier datasheets for safety-critical fits.
  • Tap drill d − P is an approximation; for hard materials or deep threads, consider lower engagement (bigger drill).
  • Clearance recommendations are typical; jig/locating fits may need tighter or looser values.
  • Low-head, button-head, and flanged socket screws use different head sizes—this tool is for standard SHCS.
FAQ & Troubleshooting

Can’t choose a fine pitch

  • Fine pitches are shown only where standard for that size (e.g., M8 has 1.25 and 1.00).

Numbers show “–”

  • Ensure a size, pitch, and valid margin are selected before calculating.

Counterbore still feels tight

  • Increase the margin (e.g., from 0.30 mm to 0.50 mm) to suit your machining tolerance and finish.

Tap feels heavy

  • Use coated taps, cutting fluid, or increase drill size slightly to reduce engagement in tough materials.

Copy-Paste Mini Workflow

1) Pick nominal size (e.g., M6)
2) Pick thread pitch (e.g., 1.0)
3) Set counterbore margin if needed (e.g., +0.30 mm)
4) Press Calculate
5) Use: dk, k, hex key s, clearance Ø (close/normal/large), counterbore Ø & depth, and tap drill ≈ d − P