Metric Bolt Sizes/Threads Explained

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Metric Bolt Sizes/Threads Explained

Postby Gman » Sat Sep 13, 2008 9:40 pm

The CX/GL bikes being Japanese mean that 99% of the nuts and bolts on the bikes are Metric with Metric pitch.

When reading the workshop manual be careful when you are checking on the Torque values of none specific bolts as it can be confusing.

When you see a bolt size listed as say 6mm this means the shank of the bolt is 6mm,not the head.
Bolts are never measured by their head!

The two critical dimensions of bolts are the shank size and it's thread.The length and head size are secondary.Torque is always set by the shank size and thread and lastly by the depth/length of the bolt and the materials.

Metric bolts are normally designated/advertized as M6/M8/M10 etc.This is the shank size in millimetres
Metric bolts can have the same shank size but a different pitch/thread.

AFAIK the M6 bolt with a 1.0mm coarse thread is the most common bolt used on the CX/GL engines(I don't have a thread/pitch gauge so this was measured with vernier calipers so I will stand corrected) like the 5 used on the clutch cover and the 13 on the front engine casing etc.

Makers/suppliers can confuse the issue by calling some of the threads Coarse/Medium and Fine.

If you look at the chart below under the M6 section you will see that it comes in two threads/pitches e.g 1.0mm and 0.75mm
Ignore their spanner/wrench sizes on the right as many M6 bolts have an 8mm Hex head on these bikes.


This is only a concern when sourcing a Tapping tool for re-doing threads that have stripped and the same for a Heli-coil kit or if you want to buy after market screw/bolt kits like Titanium ones etc,

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