Counterbore Hole Size for Pan Head (ISO 7045)

Counterbore-hole-pan-head-iso
Unsure on what size counterbore hole to use for your ISO pan head fasteners?

Then look no further!

This short post will give you the exact dimensions you need for your screws and bolts.

Jump to Chart

A counterbored hole is usually used for when the top of a screw or bolt needs to be flush with, or sit just beneath, the surface of the material it is inserting.

For example, a pan head screw with a counterbored hole sits flush with the surface, whereas the pan head screw with a simple clearance hole sits above the surface:
 

Counterbore-vs-Clearance-Hole-Pan-Head-3D

An example of a pan head and the corresponding counterbore hole is shown in this 3D model:

Counterbore Hole
Pan Head Screw

Use the image and chart below to determine what dimensions to use, all dimensions are in millimetres.

For example, an ISO 7045 M8 pan head bolt with a normal fit counterbored hole will require a pilot hole diameter of 9 mm, a counterbore diameter of 18 mm, and a counterbore depth of 6.8 mm.

Counterbore-dimensions-section-view-drawing

Counterbore Hole Size Chart for Pan Head Fasteners (ISO 7045)

All dimensions are in millimetres.

Fastener Size

Pilot Hole Diameter (Close Fit H12)

Pilot Hole Diameter (Normal Fit H13)

Pilot Hole Diameter (Loose Fit H14)

Counterbore Diameter

Counterbore Depth

M1.61.71.82.03.51.5
M22.22.42.65.02.1
M2.52.72.93.16.02.6
M33.23.43.67.02.9
M44.34.54.89.03.6
M55.35.55.811.04.5
M66.46.67.013.05.4
M88.49.010.018.06.8
M1010.511.012.024.08.3

If you want to learn more about counterbored holes, see our post here.

Looking for a Different Standard of Counterbore Hole?

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