bolt size

katsmom · **Posted:** Tue Oct 16, 2012 9:06 am

Can someone explain what an M3 bolt is. Size and all that?

KelvinS · **Joined:** Mon Mar 30, 2009 5:13 pm

M3 just refers to a nominal metric diameter of 3mm, but the length can vary. For example, an M3x20 bolt has a 20mm long shaft (excluding the head) that is 3mm in diameter. Hope that helps.

Andreas Nortmann · **Posted:** Tue Oct 16, 2012 9:22 am

http://en.wikipedia.org/wiki/ISO_metric_screw_thread

EDIT: Kelvin was faster.

Tony Fisher · **Joined:** Sun Mar 27, 2005 7:37 pm

katsmom wrote:

Can someone explain what an M3 bolt is. Size and all that?

Be careful, If someone says you need a M3x5 for example and you go to a shop and ask for one you might well end up with the wrong head because there is pan head, round head, truss head, countersunk or flat head, oval or raised head, bugle head, cheese head, fillister head, flanged head. The last thing you want to do is get your flanged head muddled up with your bugle head. There are also numerous different tops other than slot and phillips. In my experience it's best to actually see which screw you require.

KelvinS · **Joined:** Mon Mar 30, 2009 5:13 pm

Tony Fisher wrote:

katsmom wrote:

...there is pan head, round head, truss head, countersunk or flat head, oval or raised head, bugle head, cheese head, fillister head, flanged head.

...and of course there are also different materials: brass, steel, galvanized steel, jelly, etc. Well, OK, not jelly.

Gus · **Posted:** Tue Oct 16, 2012 4:54 pm

And many different types of thread, normal, tap-tight, self tapper ...

KelvinS · **Joined:** Mon Mar 30, 2009 5:13 pm

And different temperatures: hot, cold, warm, slightly chilled, tepid ... choosing just the right temperature can be very tricky.

bolt size

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