On Mon, 22 May 2017 21:12:33 +0100, newshound wrote:

On 5/22/2017 8:03 PM, James Wilkinson Sword wrote:
On Mon, 22 May 2017 19:49:21 +0100, newshound
wrote:

On 5/22/2017 6:14 PM, James Wilkinson Sword wrote:
On Mon, 22 May 2017 17:47:34 +0100, harry
wrote:

On Monday, 22 May 2017 15:40:59 UTC+1, James Wilkinson Sword wrote:
Are screwnails still used? What advantage do they have over screws?

The advantage is you can hammer them in

You can hammer screws in. I know somebody who does that quite
successfully.

Oh, an idiot

He'd only be an idiot if it failed. They go in fine with a hammer, and
they screw back out. Screws are basically screwnails, plus the ability
to remove them with a screwdriver.

and they won't easily pull out. Cheaper

Why would they be cheaper when the only difference is the presence of a
pozidrive head?

That's quite a big difference.

Surely they're all made in a mould. Same price once you've made the mould.

OK, I will bite. What sort of "mould" do you think is used to make these
various types of fastener? The key point in this case is that a
screwnail just needs a crudely made flat head, like a nail. Whereas the
pozidrive needs a very accurately formed socket, so that it is a good
fit with the screwdriver bit.

And both need a helix shape.

Also, they tend to be mild steel, like
(ordinary) nails whereas proper screws are carbon steel and quite a bit
stronger.

So something you bash in with a hammer doesn't need to be so strong?!

No, in fact it doesn't. As long as it is hammered fairly accurately, it
is in pure compression. It only has to be stronger than the wood, which
is why you can make nails out of copper.

The torsional stresses on a screw head can be high, especially with an
impact driver. This is why harder materials are used.

Funny how nails bend easily, yet screws never shear with rotational torque.

Anyway, since screws and nails are a tiny tiny proportion of the cost of
building something, there's no point in scrimping on them.

You've never built anything using Turbo Gold or Spax screws, have you.
Not a negligible part of the materials costs.

I use regular screws, sometimes double helix fast screws, they work fine. You can buy 1000s for the cost of the rest of the materials.

--
Paper clips are the larval stage of coat hangers.