Bolt & screw clearance hole chart.

How to use this

Which fit do you need?

The clearance hole is the through-hole in the part the fastener passes through; the mating threaded hole is sized from a tap drill chart. Pick the fit by how much positional freedom the joint can tolerate.

• Close fit — tight alignment

  Smallest clearance. Use when the bolt must locate the parts precisely (shear-loaded joints, dowel-like positioning, single-fastener brackets where the hole sets position). Demands accurate hole locations and good true position — there is little room to absorb tolerance error. See true position.

• Normal (standard) fit — general purpose

  The default for most assemblies. Enough slack to assemble easily while keeping reasonable alignment. If a drawing just says “clearance hole,” this is almost always what is meant.

• Loose (free) fit — maximum slack

  Largest clearance. Use for multi-fastener bolt patterns (tolerance stack across many holes), parts that grow with temperature (thermal expansion of dissimilar materials — see thermal expansion), field-assembled or as-fabricated structures, and anywhere holes are drilled without precise jigging. The trade-off is reduced bearing area under the head — add a washer if the head could pull through.

• Clearance hole vs. tap drill

  They are opposites. A clearance hole is larger than the fastener so the bolt slides through with no thread engagement. A tap drill is smaller than the fastener — it leaves material for the tap to cut internal threads into. Drilling a clearance hole where you needed a tap drill (or vice-versa) is a common and costly mix-up.

• Counterbore & countersink go on top

  For socket-head cap screws and flat-head screws, the clearance hole is paired with a counterbore or countersink so the head sits flush or recessed. Body clearance comes from this chart; head recess dimensions come from the countersink & counterbore chart.