A4 stainless

[noel shelleyParticipant @noelshelley55608]

We are spoilt with so many choices . I live on the coast and much of the decking round the caravans is 10+ years old some I have dismantled to re use. It is screwed together with a square drive and a strange green coating that seems rust proof. I have saved a load of them to re use the coating has worked that well. As for stainless be it A2 or A4, they may be cheaper than bronze but you NEED to understand them and HOW to use them. Noel.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, I know that A2 stainless won’t fair well with Sulphuric acid over a long period, but A4 stainless does. Food preparations done on stainless steel surfaces, should always use 316 grade. Strangely, stainless steels don’t resist abrasive materials, like sand, as long as mild steel does.

Regards Nick.

[noel shelley]

On noel shelley Said:

We are spoilt with so many choices … you NEED to understand them and HOW to use them. Noel.

Very true!  There are many different Stainless Steels, and it pays to choose the right one for the job.   It’s about the specification, not “quality” or where it was made.

This table summarises some of the common alloys.   Some prioritise corrosion resistance over strength, others strength over corrosion resistance.  In practice designers also go for the cheapest alloythat will do the job, and what that is may not match our expectations!   Don’t assume an unknown stainless will be either strong or corrosion resistant!

I assembled the table from a blurred web image – any mistakes are mine!  “Workshop Materials” by Alex Weiss is recommended (Workshop Practice Series No 30.)   Much more informative than believing in “quality” or assuming that everything made in China is rubbish!

A wood-screw might be made of:

• 304 for cheapness and good corrosion resistance, but it’s not strong and no good at sea.
• 303 for strength, but not in a corrosive environment
• 316 for marine use because it resists salt

So, when it matters, buy screws to suit the application, ideally those that say what alloy they’re made of.   Unspecified screws sold cheap in DIY stores and online may not be good enough.

Dave

 

[David Ambrose]

On David Ambrose Said:

I had drilled clearance holes, as I usually do. I can’t see how a fully-threaded wood screw can join two bits of wood tightly unless you do, but many people don’t seem to bother.

There are special decking screws with a faster thread at the top specifically to pull the boards down.
Interesting that people are mentioning pilot holes, reversing to pickup the thread, and use of candle wax – things we all learned before our teens in my generation. By the way if you can find a church burning 7 day saint’s candles see if you can get a used one off the warden. They end with 1/4″ of soft wax at the bottom that is better than normal hard wax for lubrication ad waterproofing tasks.

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