Stainless steel screws brittle?

[Albumen]

Just had a SS screw (3.5 x 20mm) break on me. Drilled pilot hole, into oak. Pain in the neck getting the stub out. Had to drill round it and will have to fill. The way this project is I can't just move the holes anywhere else.

So I don't want this to happen again. It felt a bit tight, but not that much. I was outside, so not much above freezing.

Are SS screws more brittle than ordinary?

 

[Deleted member 174758]

Yes. Best approach is not to use an impact driver at all, pre-screw with an ordinary steel screw (which is removed and replaced with the s/steel one after) and to add a lubricant (e.g. soft soap, candle wax, etc) to the threads

 

[Albumen]

Many thanks. I was actually screwing it by hand. Maybe I'm stronger than I thought! But it's only a 3.5mm, going into hardwood, so easy to break.

It doesn't actually need to be SS, it's mounting coat hooks, in doors. Just that the coat hooks are SS so used SS screws for look. But ordinary bright steel will probably look OK. Will follow your advice about lubricant.

But was there something about steel staining oak I read once?

 

[Burnerman]

Genuine stainless steel of high quality doesn't stain oak, of course ordinary steel screws do.....it all depends on the quality of the screw!
Go for stainless, brass or even bronze (if you can still get those), pilot hole first followed by a quality wood screw with lube......finishing with the stainless if that suits you.
John

 

[Deleted member 174758]

Many thanks. I was actually screwing it by hand. Maybe I'm stronger than I thought! But it's only a 3.5mm, going into hardwood, so easy to break.

But was there something about steel staining oak I read once?

Actually, stainless steel is softer than the near mild steel they make conventional steel screws from. In that respect it's like brass - which was the traditional choice for nomn-staining fittings on oak, walnut and mahogany. The reason is that those three timbers contain large amounts of natural tanin; tannin + water (and a bit of diluted hydrogen sulphide in rainwater making sulphuric acid) = tannic acid; tannic acid + iron (as in mild steel screws) = black ferric oxide, a semi-permanent black stain. Which is why you need stainless steel or brass scerws for oak. Amazing what you learn at college........

 

[Albumen]

Thanks. I've bought some of those Spax hardened steel self cutting things. They're actually a goldish colour, but I can live with it. It's a coat rail for Pete's sake. Most of the screws will be covered with coats. It's indoors, not sure how much moisture it's going to get.