how do I read thread sizes

[Dave]

I have a bolt that is m12x1.5x65. I know what the 12 and the 1.5 mean - what is the 65???

I am looking for a heli-coil insert for it and trying to determine the significance of that number.

[MattE30]

I'm going to take a shot in the dark, but could it possibly the number of threads the bolt has?

[Jordan]

Length of the bolt in mm.

[DanGillan]

yep ^^

[AdamF 88iS]

Thread width, pitch, length.

[EverWiser]

M12 = 12mm diameter...1.5 = 1.5mm between threads (thread pitch)...65 = 65mm long screw. European terminology dictates that if it "screws" into a threaded hole, it's a screw. If it has a nut on the end of it and "bolts" through a non-threaded hole, it's a bolt. Lesson over...