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tony

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I have to say 90% of the time I'd opt for a screw, I just feel it gives me more control

on this occasion I'd go for a nail, however I think the spacing of the T and G is maybe more important
By spacing , do you mean not clamping the boards together tightly. If I do nail it , what nails do people recommend & should I nail through the boards into the braces or the other way round. Thanks Tony
 

Jake

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nails are generally made of steel, screws are generally made of steel, I’m not seeing how the two are going to behave differently other than a second moment of area difference the length that can flex is so small even that would be negligible.
(Generally speaking) screws are hardened, nails are not, so the latter have better shear strength.
 

TheTiddles

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(Generally speaking) screws are hardened, nails are not, so the latter have better shear strength.
Why would hardening reduce shear strength? For steel USS is about 0.6 to 0.8 UTS, so if I hardened the steel increasing tensile strength I’d expect an increase in shear strength too, but also a reduction in ductility.

Either way this is kinda navel gazing as the wood will probably yield before the fastener by splitting or bending the frame it’s attached to, so back to the original question... screws or nails, it don’t matter just put one in the middle of each board and leave a small gap between each one to allow for them to go out and in with the weather and they should be just fine

Aidan
 

Jake

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Probably just repeating 'received wisdom' so the mechanism may be wrong, but they are rated (by structural engineers not lawyers) as better in shear.

I agree spacing the boards in this application is far more important.
 

XH558

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Errr, what about the Twisted Manchester nails? You know the ones with either the slotted heads or the posher Philips/Posidrive heads?

They are very clever and provide a superb fixing.
 

TheTiddles

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Probably just repeating 'received wisdom' so the mechanism may be wrong, but they are rated (by structural engineers not lawyers) as better in shear.

I agree spacing the boards in this application is far more important.
Yes, I’ve seen it written a few places, seems they are confusing shear strength with ductility, nails are more ductile but have less shear strength.

There’s an interesting video here...https://youtu.be/qmajKElnwfE

not a bad test really, the screws demonstrate higher shear strength than nails in just about all cases, he too mixes up shearing and failure in bending though

Aidan
 

TheUnicorn

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Yes, I’ve seen it written a few places, seems they are confusing shear strength with ductility, nails are more ductile but have less shear strength.

There’s an interesting video here...https://youtu.be/qmajKElnwfE

not a bad test really, the screws demonstrate higher shear strength than nails in just about all cases, he too mixes up shearing and failure in bending though

Aidan
that was an interesting video, the third test proves what i thought before, but really the other tests are perhaps more relevant as they would come closer to real world stresses, not what i expected
 

Jake

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There is some interesting material in here. Wood Handbook--Chapter 7--Fastenings (fs.fed.us). It seems that until 1991, the US standards relied on some empirical tests which gave what seem to be pretty radically different shear results for nails versus screws (if I follow table 7-4 correctly). Then they switched to calculated values, and I can't see any factors in the equations which would lead to dramatically better performance for nails over screws in those (Table 7-5, again if I follow that correctly).

That's all with root dimension being equal, so for fixings like joist hangers and nail plates which fix the max outer diameter, nails will have an advantage which may be another tributary giving rise to this belief.
 

Terry - Somerset

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My rather simple mind comes quickly to the conclusion that screws are typically larger diameter compared to same length nails.

So I wold expect them to have greater absolute resistance to sheering even if a screw might lose out to a nail of the same diameter.

And after a few years when ferrous oxide has replaced much of the bright and shiny (stainless and brass excepted) there will be much more screw left.
 

Marnee

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It's funny how you go through life and then some one like Unicorn makes a statement - nails are maileable, screws aren't - that is so obvious but I'd never thought of before.

One point - where you do use screws, use stainless steel (brass OK but not so strong).
I couldn’t for the life of me work out why you could post nails but not screws? Then realised the typo!!! Mailable instead of malleable!!!😂😂😂😂😂
 

Marnee

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I couldn’t for the life of me work out why you could post nails but not screws? Then realised the typo!!! Mailable instead of malleable!!!😂😂😂😂😂
Maileable I should have said - outing correct system!!!!!!!
 

gmgmgm

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Is this why fencing is usually nailed? I've never seen post and rail screwed (though admit to using screws for a couple of repairs, which is probably a bad idea).
 

TheTiddles

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Is this why fencing is usually nailed? I've never seen post and rail screwed (though admit to using screws for a couple of repairs, which is probably a bad idea).
Nope, nails are cheap and fast, why not use them?
You could use screws just as well, maybe slightly less secure but if your assailant has a screwdriver they’ve got a crowbar too
Aidan
 

smackie

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The spacing on the T&G is definitely key here. You need enough tongue on the boards to allow for the expansion and contraction without having them pop. A few years ago I watched an old carpenter space T&G boards for a gate using taper matches as packers in the top and bottom of the groove to prevent the boards snugging up too much. Nailed the vertical T&G boards into the rail and removed the packers...
 

Rich C

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I really don’t think this is right, nails are generally made of steel, screws are generally made of steel, I’m not seeing how the two are going to behave differently other than a second moment of area difference the length that can flex is so small even that would be negligible.
There's steel and then there's steel. It's a broad group of materials. Nails are going to be mild steel, screws some type of hardened steel, so different material properties are expected.
 

TheTiddles

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There's steel and then there's steel. It's a broad group of materials. Nails are going to be mild steel, screws some type of hardened steel, so different material properties are expected.
Very true and those hardened steels would have greater shear strength than the mild steel of the nails

Aidan
 

Jacob

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Hi , I am reasonably inexperienced compared to the people on here & I'd like some advice. A friend has asked me to make a small garden gate , I have some spare t & g boards & I will put a couple of rails & brace on it . I believe the correct way is to screw the outside boards & then to (clench) ? nail the inner ones . I know it's only a small project but nailing it by hand is time consuming and wondered if I there is an easier option. What would happen if I screwed all of the boards . Thanks, Tony
If you screw all the boards it would take longer and screws are more expensive than nails. A trad nailed together ledge braced and battened door, or similar gate, are about the fastest things you can make. Once you've got everything cut to length, laid out etc. 20 minutes frantic nailing and clenching, job done.
 
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