Warning for Biltema's decking screw

[Anders_Nilsson]

Most understand (at least I do) that A2 is stainless decking screw and A4 is acid-resistant.

For it is decking screws we're still discussing, right?

Is there any hardened non-stainless screw labeled A2 or A4?

Yes, Biltema has several options:
Decking Screw C4 - Biltema.se
I don't know if it is hardened, but the text says it is C4 and for tougher environments, stainless alternatives are recommended.

 

[Huddingebo]

Most people understand (at least I do) that A2 is stainless decking screw and A4 is acid-proof.

Because we are still discussing decking screws, right?

Is there any hardened non-stainless screw labeled A2 or A4?

Yes, who claimed otherwise?
But A2 and A4 still only indicate the corrosion class of the screw, NOT the tensile strength of the screw.
There are many ways to achieve different strength classes in screws.
Whether it is hardened or not says absolutely nothing about the achieved tensile strength.

 

[Anders_Nilsson]

Yes, who has claimed anything else?
But A2 and A4 still only indicate which corrosion class the screw has, NOT the tensile strength class of the screw.
There are many ways to achieve different strength classes in screws.
Whether it is hardened or not says absolutely nothing about the achieved tensile strength.

I blame Coop's coffee. It contains too little caffeine. Now I see that you wrote A2/A4.. Mixed it up with C4.

It's probably easiest to buy from a better brand.

 

[Violina]

To my knowledge, regarding 1.4404 and 1.4401 (the type of steel likely used for A2 and A4 graded decking screws), they have exactly the same mechanical properties, but different resistance to corrosion. In other words, one does not break more easily than the other when screwed in.

The most important thing (as usual) and which many do not seem to understand when building their deck is that you absolutely should not screw the screws in too far and/or too hard. It affects the strength of the wood, but most importantly, you risk exceeding the yield point and then the breaking point of the material in the screw. And in this respect, I don't think Biltema's screws are worse than any other screws, they probably have similar values for these since they are almost certainly made of the same kind of material.

What I do think might differ somewhat is the design of the screw, which could mean you need to use more force to screw in a Biltema screw and thus more easily (if you're an enthusiastic amateur) "overdo it" and consequently break the screws.

 

[Jonas Persson]

one must use more force to pull on a Biltema screw and thus more easily (if you are a happy amateur) "overdo it" and thereby snap the screws.

Everyone knows that a nail breaks if you bend it a few times. A similar load occurs with the new very powerful impact drivers, they shear the screw many times per second when striking.

I want to argue that they should only be used for very coarse screws; stressing delicate decking screws that don't even need a powerful screwdriver is just silly.

 

[Huddingebo]

I claim that if a metal screw breaks after being screwed into pine/spruce, it is made of substandard material.

 

[Dan_Johansson]

I claim that if a metal screw breaks after being screwed into pine/spruce, it is made of substandard material.

That's probably simplifying it a bit...

There are some characteristics we desire that aren't easy to combine in a screw...

We want a reasonably small diameter so the screw is as inconspicuous as possible.
We want good resistance to corrosion.

 

[Huddingebo]

A small head and corrosion class are absolutely no obstacle to manufacturing a screw with sufficient tensile strength. Even though "stainless" usually holds a lower class.

 

[Violina]

Everyone knows that a nail breaks if you bend it a few times. A similar strain occurs with the new very powerful impact drivers, they shear the screw many times per second when they strike.

I would argue that they should only be used for very coarse screws, stressing delicate deck screws that don't even need a powerful screwdriver is just silly.

Quite similar to my opinion, actually

 

[Violina]

A small head and corrosion class are absolutely no obstacle to manufacturing a screw with sufficient tensile strength. Even though "stainless" usually holds a lower class.

Now it feels like you don't quite understand what you're talking about..

The tensile strength of a screw depends on its material properties, and if you think about the properties desired in (especially) a decking screw, these are not entirely compatible.

It's definitely possible to manufacture a screw that has all the desirable material properties, but the problem is that it would be quite expensive..

The question is, how well do you think that type of screw would sell?

Because that's also an important (maybe even the most important) feature of a screw, the price.

Especially when considering the fact that people who actually know how to properly drive a screw rarely have the mentioned problem of every other screw breaking...

 

[Huddingebo]

Now it feels like you don't quite understand what you're talking about..

The tensile strength of a screw depends on its material properties, and if you think about the properties desired (especially) in a decking screw, these are not entirely compatible.

It is absolutely possible to manufacture a screw that has all the desirable properties concerning its material properties, but the problem is that this becomes quite expensive..

The question is, how well do you think that type of screws would sell?

Because that is also an important (perhaps even the most important) property of a screw, the price.

Especially when considering the fact that people who actually know how to properly drive a screw rarely have the mentioned problem where every other screw breaks..

You are talking to a mechanical engineer who has studied strength of materials and screw elements etc. at fairly high levels.
It's clear that the market is full of screws, with varying strengths at different prices.
What exactly are you trying to say?

That price is the most important factor for you?

 

[Jonas Persson]

Now it feels like you don't really understand what you're talking about..

The tensile strength of a screw depends on its material properties, and if you think about the properties desired in (especially) a decking screw, they are not entirely compatible.

It is absolutely possible to manufacture a screw that has all the desirable properties in terms of its material properties, but the problem is that this becomes quite expensive..

The question then is, how well do you think that type of screw would sell?

Because that is also an important (perhaps even the most important) attribute of a screw, the price.

Especially when you consider the fact that people who actually know how to properly fasten a screw rarely have mentioned problems with every other screw breaking..

Again, does anyone seriously believe a place like Biltema sells screws year after year that break?

Of course, there are bad examples or possibly an entire batch.

About five years ago, Byggmax sold their own screw from China in blue boxes. It was junk, had a box with 6x120 for instance, and they were crooked. I haven't seen their own brand since then, only Heco.

No company with a store in Sweden sells junk, it doesn't work because customers return the products. Bad screws are possibly sold on Chinese websites where consumer laws don't reach and that have millions of other customers to deceive.

 

[Jonas Persson]

You are talking to a mechanical engineer who has studied strength of materials and screw elements, etc., at quite high levels. It is clear that the market is full of screws, with different strengths at different prices. What exactly are you trying to say?

Is the price the most important thing for you?

Then you also understand what forces a screw exposed to, for example, a knot is subjected to when the screwdriver strikes many times per second.

These forces do not arise with a classic slow-spinning screw machine. Why should one pay more for a screw just because it can withstand being screwed in with impact?

 

[Violina]

You're talking to a mechanical engineer who has studied strength of materials and screw elements, etc., at quite high levels.
It's clear that the market is full of screws, with different strengths at different prices.
What exactly are you trying to say?

That price is the most important thing for you?

That it usually depends on the nut behind the wheel

 

[Violina]

Again, does anyone seriously believe that, for example, Biltema sells screws that break year after year?

Of course, there are bad specimens or possibly a whole batch.

Maybe five years ago, Byggmax sold their own screw from China in blue boxes. It was junk, for example, I had a box with 6x120, and they were bent. I haven't seen their own brand since then, only Heco.

No company with a store in Sweden sells junk; it's not possible because customers will return the products. Bad screws are possibly sold on Chinese websites where consumer laws don't reach and which have millions of other customers to deceive.

No, I don't think so, that's the point