Screw Dimensions

[last updated: 2025-09-15]
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• Many of these dimensions are from my measurements. As such, their accuracy is not guaranteed.
  In fact, with sheet metal screws in particular, there are no industry standards for some of these parameters, such that they vary from manufacturer to manufacturer.
  Bottom line: treat them as nominal/estimates.
• Dimensions are in mm unless noted.
  
  

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• General:
  • above 1/4", screw sizes are designated in fractions of an inch
  • below 1/4", sizes are designated as "gage" numbers
  • diam of gauge screw sizes is:
    diam = 0.060" + (0.013 x #)
  • flat head sounter sink is angled at ~ 60deg from horiz
  • drill-to-clear diam is (most likely) different for machine vs. sheet metal threads
  • sheet metal screw dimensions in general are not standardized as machine screws are,
    so actual dimensions will vary between manufacturers and batches

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• Standard Metric Sizes:
  (diam x thread pitch)
        (However note that a given metric size/diam, may have more than one "standard" thread pitch.)
  1mm x 0.25
  2mm x 0.4mm
  2.5mm x 0.45mm
  3mm x 0.5mm
  4mm x 0.7mm
  5mm x 0.8mm
  6mm x 1.0mm
  7mm x 1.0mm
  8mm x 1.25mm
  9mm x 1.25mm
  10mm x 1.5mm
  12mm x 1.75mm
  14mm x 2mm
  16mm x 2mm
  18mm x 2.5mm
  20mm x 2.5mm
  22mm x 2.5mm
  24mm x 3mm
  27mm x 3mm
  30mm x 3.5mm
  33mm x 3.5mm
  36mm x 4mm
  39mm x 4mm
  42mm x 4.5mm
  45mm x 4.5mm
  48mm x 5mm
  52mm x 5mm
  56mm x 5.5mm

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