Clearance Hole Calculator

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Close fit: minimal clearance, used where precision location matters. Normal fit: the standard for most mechanical assemblies. Loose fit: maximum clearance, easiest assembly, used in structural or painted applications.
Clearance hole diameterLoose fit
9

Recommended hole diameter for the selected bolt and fit class

Clearance added over bolt1
Clearance as % of bolt diameter0.1%
Bolt sizeM8
Dimension unitmm
Clearance hole diameter9
Clearance added1

M8 bolt - normal fit clearance hole: 9.000 mm

  • Drill a 9.000 mm hole for a M8 bolt using a normal fit.
  • This adds 1.000 mm (12.5%) over the bolt nominal diameter, giving the bolt room to pass through freely.
  • Normal fit is the standard choice for most structural and mechanical assemblies. It allows easy assembly while keeping bolt position reasonably consistent.

Next stepAlways verify the hole diameter against the actual fastener and tolerance requirements before drilling. For critical applications, consult the relevant standard (ISO 273 for metric or ASME B18.2.8 for imperial).

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