On 29 May, 15:41, dg wrote:
Apart from reasons of practicality, is there any reason for not using
coach screws instead of coach bolts for fixing large timber sections -
ie is the strength and longetivity of the fixing the same?

dg

For a start lets do the pedant thing and at least get them called by
their right names - they are "coach bolts" and "carriage screws".

The argument on sheer and tensile is cobblers as diameter for diameter
the sheer strength is going to be the same. On the other hand the
tensile strength of a bolted joint with a suitable load spreading
plate is clearly always going to be greater than a screw into the
wood. The choice is related to whether you can get at both sides of
the joint - if you can then its a bolt - if you can't it's a screw.
Can't really be simpler can it?

Rob