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Bolts
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28-03-2015 6:16am#1
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Assuming the two bolt sizes are of the same grade (8.8, 10.9, etc), M16 is rated for approximately double the load in tension of M12.
Here are the recommended loads of various fasteners:
I Newton = (approx.) 0.1 Kg, so:
3 x M12 8.8 will hold a little over 11 Tonnes
2 x M16 8.8 will hold a little over 14 Tonnes
So, 2 x M16 is about 30% stronger in tension than 3 x M12.
Moving the M12s up a grade or two reduces the gap, but never to the point of making them 'as good' as 2 x M16.0 -
Assuming the two bolt sizes are of the same grade (8.8, 10.9, etc), M16 is rated for approximately double the load in tension of M12.
Here are the recommended loads of various fasteners:
I Newton = (approx.) 0.1 Kg, so:
3 x M12 8.8 will hold a little over 11 Tonnes
2 x M16 8.8 will hold a little over 14 Tonnes
So, 2 x M16 is about 30% stronger in tension than 3 x M12.
Moving the M12s up a grade or two reduces the gap, but never to the point of making them 'as good' as 2 x M16.
Great info there..
I was basing my opinion completely on sectional area..0 -
The above info is purely based on the loads in tension.
If there are ANY other loads put into the setup (twist, sideways, etc), the forces involved get complicated very quickly.
I'd always be inclined to overdo this sort of thing to the point of ridiculousness, so I'd be thinking of going with 3 x M16 if I could fit them in at all.
Or more!
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The above info is purely based on the loads in tension.
If there are ANY other loads put into the setup (twist, sideways, etc), the forces involved get complicated very quickly.
I'd always be inclined to overdo this sort of thing to the point of ridiculousness, so I'd be thinking of going with 3 x M16 if I could fit them in at all.
Or more!
Thanks for all the info lads, I was thinking about 3 M16's but I was worried about shearing the plates with the holes so close together. plates are only 100mm wide leaving 13mm between the holes (provided the 3 are spaced evenly on the plate)0 -
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Only seeing this now, sorry for not replying sooner!
Unless you're holding up the entire roof of what I presume is a reasonably normal farm shed, it sounds like the 3 x M12 would have been plenty.
2 x M16 12.9 is probably vast overkill, which is kinda how I like it
The 100mm plate and the welds on it are likely to fail long before the bolts.0 -
I Newton = (approx.) 0.1 Kg, so:
3 x M12 8.8 will hold a little over 11 Tonnes
2 x M16 8.8 will hold a little over 14 Tonnes
So, 2 x M16 is about 30% stronger in tension than 3 x M12.
Moving the M12s up a grade or two reduces the gap, but never to the point of making them 'as good' as 2 x M16.
I got my 16mm grade 12.9 bolts yesterday. I can only put in 2 as the heads will be up against each other. still 2 of the grade 12.9 will hold 25 tonnes![/quote]
Ya hope 0 -
Only seeing this now, sorry for not replying sooner!
Unless you're holding up the entire roof of what I presume is a reasonably normal farm shed, it sounds like the 3 x M12 would have been plenty.
2 x M16 12.9 is probably vast overkill, which is kinda how I like it
The 100mm plate and the welds on it are likely to fail long before the bolts.
overkill is no harm, ya it an old hay shed and the centre 2 posts are bulging outwards (the ridge cap in sinking in the middle) still id rather sleep happy knowing that the bolts will be strong enough. thanks for posting the bolts chart, very helpful!0 -
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