Steel screw into oak.

[Bod]

I'm making a kitchen dresser type plate rack out of oak, for a narrow-boat, and am expected to fit brass cup-hooks.
The only "solid" brass hooks that suit, arrived in the post today. They have steel threads......better for screwing in, I grant.
This boat sits idle and unheated over winter, idea for the oak around the thread to go black.
As the hooks have a shoulder, I am thinking of putting a 6mm dowel into the oak then screwing the hook into that. Idea being the thread won't be in contact with the oak, and be hidden by the brass shoulder.
Good idea, or not?
The oak is 22mm thick, so I don't expect expansion of the dowel to be a problem.

Bod

 

[AndyT]

I think that would work well.
The staining happens when steel and oak are in contact and you will keep them separate. I'd be tempted to add a dab of shellac on the steel thread and at the back of the brass shoulder - probably unnecessary but it wouldn't do any harm.

 

[Steve Maskery]

Yes, I agree. Or you could use a small Rawlplug, very little chance of the screw going off centre.

 

[Phil Pascoe]

Or you could bore the holes slightly oversized and put them in with hot melt or epoxy.

 

[Mike Jordan]

Hanging mugs and other items from hooks is not really best practice on a narrow boat. It's all to easy to have the mugs come into contact with surrounding woodwork or linings as they boat moves on the water or when moving through locks.
It's not impossible to do it but bear in mind that even the gentlest contact will remove paint or varnish at a suprising rate. The worst case I have seen involved a short length of hanging chain which removed a lot of paint.
You are right about the chances of condensation on metal causing damage.

 

[ED65]

One thing to bear in mind is that threads don't hold nearly as well in end grain as long grain. I think epoxying the hooks into holes drilled directly into the oak would be a better idea here if you're going ahead with fitting them.

NOS brass cup hooks are still out there if you can afford the time to look for the real thing.

 

[Phil Pascoe]

^^^ and also the threads on cuphooks don't tend to good in the first place.

 

[xy mosian]

Not an answer but a very related question.
A lot of screws seem to be coated theses days, zinc passivation etc.. Does this make any difference to the staining problem?

xy

 

[ED65]

A lot of screws seem to be coated theses days, zinc passivation etc.. Does this make any difference to the staining problem?

In theory yes. Over time, perhaps not.

I've seen many a modern screw with that yellow zinc plating rusting in place on a fence, with neighbouring screws just as shiny as can be. But nails, bolts and nuts with thicker zinc plating (some hot-dipped) can last outdoors for years, decades even, with any amount of weather thrown at them.

So with the thinner plating there's an element of luck involved. And I think whether the wood will actually get properly wet must play a part. Just last night I was looking at some zinc-plated threaded rod fitted at the bottom of a small box easel, used to mount the ledge with a couple of wing nuts. The easel had gotten wet and where damp wood was left in close contact with the rods (no idea how long) the underlying steel rusted right through the coating, while the rest of the rod sticking out in the air hasn't a trace of rust.

 

[Phil Pascoe]

I suspect the coating gets a minute amount of damage on insertion and the screws rust from those points.

 

[Cabinetman]

This has made me rethink what I've been doing, I make a lot of things in Oak and a couple of years ago moved away from brass screws to stainless steel, I've never had a problem with black stains but then probably there hasn't been a damp problem. Does anybody know do stainless steel screws cause oak to go black?

 

[Steve Maskery]

Stainless should be OK, it's ferrous materials that are the problem.

 

[Phil Pascoe]

Stainless shouldn't cause a problem. Don't mix stainless with galvanize e.g. galvanize hinges and stainless steel screws - the reaction between the different metals will strip the galvanize.

 

[xy mosian]

Thanks all for joining in.
ED65, and others, says what I suppose I would have if only I had thought about the problem. There are so many different coatings about, Brassed, Chromed, Jappanned, etc., that unless, lengthy, tests are carried out we cannot really be sure. Let's be safe out there.
xy

 

[RobinBHM]

"Austenitic Stainless Steels for Timber Fixings
The causes of metal corrosion in wood are described and the hazard that acetic acid can be to metals when liberated from hardwoods such as oak, western red cedar and Douglas fir. Stainless steel types 1.4301 (304) and 1.4401 (316) can normally be considered for timber fixings, but timber immersed in river or seawater may require 316 or superaustenitic grades such as 1.4547 (254SMO) for fasteners. Swimming pool building roof areas are also a special case. Stress corrosion cracking (SCC) resistant grades such as 1.4539 (904L) or 1.4547 (Avesta 254SMO) must be considered for load bearing or stressed fasteners.

SSAS3.91-Austenitic Stainless Steels for Timber Fixings.pdf [93.4kb]"

Stainless steel is not completely stainless or corrosion free, the lower grades will degrade in harsh environments outside.

The biggest problem with using stainless steel screws in oak is heads snapping off, or the pozi drive mushing

 

[woodpig]

Any decent chandlers should have something suitable.

 

[Bod]

Thanks all for the replies, you've confirmed my thoughts.
With regard to the cups swinging, I'd all ready had that idea, so for the most part they're fixed.

In experiment, the boat would have to be beyond 45 degrees of list to Port before there's any danger of the bowls falling out. At this point broken crockery would be the least of your worries!
The hook(s) will be reserved for oven mitts.
Now to start sanding the router marks out.


Bod

 

[Deejay]

Any decent chandlers should have something suitable.

Woodpig is right Bod

Google 'solid brass cup hooks'

Cheers

Dave

 

[Bod]

You seen the price chandlers charge?
But yes that was the fall back position.

Bod