M

[spooky]

Can someone explain in terms I might understand about metric fasteners please.... If i have a nut and bolt that a 10mm spanner/socket fits what would that be called ?  M10 ?  likewise if I have a bolt that needs a 13mm tool what the M is that ? I want to order a mixture but not sure where to start, 

[mthee]

The M refers only to the diameter of the threaded portion of the bolt. An M6 bolt might need a 10mm socket on it, for example.

[RonXBR]

Hope this helps.

Ron.

[RonXBR]

Even bigger bolts!

Ron.

[spooky]

Thanks to you both, that`s great...     M5/6/and 8 are what i need in stock.

[iansoady]

I blame the Americans who started the rot by describing fasteners by spanner size - eg 1/2" A/F which is normally for a 5/16" diameter bolt - rather than everyone else who uses the threaded siameter eg metric and BSF / Cycle etc. That chart from Ron is quite helpful. For some reason the Japanese manufacturers use different head sizes to the standard ISO ones - 12mm as opposed to 13mm for 8mm bolt diameters.

The Americans in their usual fashion, refer to their sizes as "standard".....

[mthee]

Also important to note the Japanese Industry Standard (JIS) screwdriver against Phillips, as described here;
https://www.motorcycle.com/ask-mo-anything/difference-between-japanese-jis-phillips.html

[iansoady]

Yes indeed. I like many others must hasve ruined countless screw heads before I found this out a few years ago. My rule of thumb is: JIS will sort of work in Phillips, Phillips will work in Pozidriv. But NEVER the other way round.