M8 Bolt Size and Thread Specifications
What is an M8 bolt?
An M8 bolt has 8 mm nominal diameter with 1.25 mm coarse pitch in standard ISO tables. Fine pitch 1.0 mm is common when drawings call for it.
M8 is a widely used metric bolt size in machinery, automotive, and structural applications. An 8 mm nominal diameter with 1.25 mm coarse pitch provides strong threads and is easy to source. Spanish reference: perno M8.
Specifications
| Specification | Value |
|---|---|
| Nominal diameter | 8 mm |
| Standard pitch | 1.25 mm |
| Fine pitch | 1.0 mm |
| Tap drill size | 6.8 mm |
| Closest imperial equivalent | 5/16-18 |
Hex head size
| Bolt size | Hex head size |
|---|---|
| M8 | 13 mm |
Common uses
M8 bolts are common in machinery mounts, automotive assemblies, structural connections, and general hardware. They are a standard choice for medium-duty fastening.
Related tools
Related charts
FAQ
What is the standard pitch for an M8 bolt?
The standard pitch for M8 is 1.25 mm. Fine pitch is 1.0 mm.
What drill size should be used for tapping M8 threads?
For M8 x 1.25 coarse thread, use a 6.8 mm tap drill.
What imperial bolt is closest to M8?
5/16-18 UNC is the closest imperial equivalent to M8.
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