M9 Bolt Size and Thread Specifications
Quick answer
M9 bolts use 9mm major diameter with 1.25mm coarse pitch in typical tables.
They bridge M8 and M10 for some industrial and automotive lines.
Use the tables below and tap drill size checks from the calculator when pitch varies.
M9 is an intermediate metric size that is not as widely stocked as M8 or M10. Always verify pitch and strength class against the original part. Spanish reference: perno M9. For tap drill size, thread types, and thread identifier workflows, pair this page with tools as you verify threads.
Specifications
| Specification | Value |
|---|---|
| Nominal diameter | 9 mm |
| Standard pitch (coarse) | 1.25 mm |
| Fine pitch | 1.0 mm |
| Tap drill size | 7.8 mm |
| Closest imperial equivalent | between M8 and M10 |
Hex head size
| Bolt size | Hex head size |
|---|---|
| M9 | 14 mm |
Common uses
Imported machinery, specialty equipment, and applications where documentation specifies M9. Cross-check loads with the bolt size chart and screw size conversion when you mix metric and inch bins.
Related tools
Related charts
M9 vs M10 bolt size
Shank diameter and pitch set tap drill, hex key, and strength for each ISO size. Compare values in the tables above with the M10 bolt size page when you resize hardware.
Use the bolt size chart when you compare hex and shank columns across sizes.
Metric vs UNC thread size
Metric threads list diameter in millimeters and pitch in millimeters per thread; UNC lists nominal inch diameter and threads per inch. They are not interchangeable—taps, dies, and gauges differ.
Read metric vs unc thread context when series labels are unclear.
Use screw size conversion when you must match stocked parts.
M9 specifications and tools
How to choose the right bolt size
Choosing the correct bolt size depends on load, material, and thread type. Larger diameters increase strength, while thread pitch affects holding force.
Use the bolt size chart to compare shank and hex dimensions before you standardize hardware.
Use tap drill size guidance when you plan tapped holes.
Use the thread identifier when stamped sizes are missing.
FAQ
What is the standard pitch for an M9 bolt?
The common coarse pitch for M9 is 1.25 mm. Fine pitch is often 1.0 mm where specified.
What drill size should be used for tapping M9 threads?
For M9 x 1.25 coarse thread, use approximately a 7.8 mm tap drill. Use our Tap Drill Calculator for other pitches.
What imperial fastener is closest to M9?
between M8 and M10 is a practical reference for comparing M9 to inch hardware; verify fit for your application.