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easy method to groove stainless rings / Ubolts 18-Sep-2008 At 7:17:53 PM rprznt

Message

On 18/09/2008 atreyudelacy wrote:
>Where the tensile and shear capacity is governed by area (r ^ 2), the bending capacity is >governed by what's called the 'moment of inertia' (r ^ 4, i.e A 10mm bolt with 1.25mm deep >thread - i've taken this to mean that the min diameter will equal 7.5mm - will only have 32% >of the bending capacity that a plain 10mm bolt would),this leads back to the significance of reducing the diameter of the bolt.

some notes on bolt threads....

metric threads are described like this: M10 x 1.5
this means that the thread outside diameter is 10 mm and the pitch is 1.5 mm
(the pitch is the distance between two crests or two valleys on the thread.....)
the minor diameter is easily worked out using this formula md = od - 2(0.54*p)
so for m10 x 1.5 (which is ISO standard) md = 8.92mm.

>Given that the R8 (316 SS) anchor in steve's tests did not even meet the
>min requirements, i would suggest that it would be very dangerous to have
>a minimum diameter (taken at the thread, not at the shank) less than 8mm,
>ideally not less than 10mm.

to continue with what you were saying, an m12 x 1.75 (ISO) bolt might be suitable in this situation, as it has a minor diameter of ~ 10.11mm.....

.... but i don't really see how the minor diameter of the thread affects the shear and/or tensile strength of the bolt, glued in as fixed protection....
my opinion is the bolt head will shear off, not break through the thread, safely still stuck in the rock.

cheers dan