Metal Fixings in Oak

[E-wan]

Do all metal fixings screws bolts ETC in oak needs to be Stainless Steel?

I've heard that the tannic acid in oak will react with the metal but not sure if this is a cosmetic concern or whether it will actually eat through the metal in time.

I'm planning a new back gate which will involve fixing some 3x6 pieces of oak into brickwork. The structure will be exposed to the elements and get fairly wet.

If they do you need to be stainless does it matter if it's A2 or A4 grade?

Thanks

Ewan

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[Keith 66]

Having been a boatbuilder most of my life i have seen a lot of stainless steel used, To be honest Stainless is probably going to corrode in oak because of the tannic acid. A2 grade probably faster than anything else, Galvanised bolts are probably as good as anything if well greased.

 

[Sawdust=manglitter]

Regardless of the oak tannins effect on steel, due to the exposed environment of your application I would definitely use stainless fixings.

A2 stainless steel may tarnish after a while but will still resist corrosion, whereas A4 stainless is more resistant to things like salt water and will hold a shine for longer, so if there isn’t a huge difference in price I would lean towards A4 for piece of mind

 

[Mike Jordan]

The critical ingredient is moisture, if the steel fixings are into dried oak as in internal furniture, no serious corrosion should occur. In your instance non corroding fixings are preferable. My knowledge of stainless grades is limited but I suggest that you visit a local boat chandlers, they sell stainless screws in small quantities.

 

[E-wan]

Cheers for the quick replies

I always use A4 when repairing or modifying my boats and have plenty of A4 bolts in a variety of sizes.

Can anyone suggest a supplier of large A4 countersunk screws in small quantities. Suppliers I've seen from a brief Google search seem to want you to buy at least 100 in eack size.

Chandlers can be a little over priced and tend not to have screws as large as I anticipate needing for this project.

Thanks

Ewan

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[MikeG.]

The one thing to beware of with stainless screws is that they are weaker than ordinary fittings, and it is extremely easy to twist the head off. Even an old fashioned manual screwdriver will do it, but cordless drivers to it for fun. So all fixings need a pilot hole, and a countersink if necessary, and if you need them to go in really tight then wax them first. Don't rely on screws to pull boards up, or tighten joints: do it with a clamp, then retain with a screw. They're probably no stronger than brass screws.

I have certainly experienced corrosion in seasoned oak, too......just not at the same rate as with green oak. Oh, and treat all finishes on ordinary fixings as extremely temporary. "Passivated" is my bug bear. I think of this as nothing more than a fancy colouring. It doesn't last 5 minutes in even the mildest of circumstances.

 

[Phil Pascoe]

Don't for any reason mix galvanise and stainless, such as s/s bolts and galvanised washers - the reaction between the two will strip the galvanise. Damhikt.

 

[Paul200]

"Passivated" is my bug bear. I think of this as nothing more than a fancy colouring. It doesn't last 5 minutes in even the mildest of circumstances.

I'm pretty sure the passivation is an antifriction coating Mike. The screws are normal electro plate underneath.

 

[user22161]

Can anyone suggest a supplier of large A4 countersunk screws in small quantities. Suppliers I've seen from a brief Google search seem to want you to buy at least 100 in eack size.

Chandlers can be a little over priced and tend not to have screws as large as I anticipate needing for this project.

Thanks

Ewan

Sent from my SM-G900F using Tapatalk

Have a look at Seascrew

https://www.seascrew.com/browse.cfm?STA ... 0000000019

 

[AES]

If it's any help, I can vouch for the fact that it's pretty easy to twist the heads off "standard" SS wood screws. You need a VERY low clutch setting and ideally, finish off by hand (needs a good sense of feel though - which DOES develop pretty quickly after you've twisted the heads off 3 or 4 screws though)!!!

Don't know anything about sea-going varieties though.

 

[Beau]

If aesthetics are not an issue dont worry. Yes you will get some blue/black staining but never had steel fixings corrode through due to the reaction. Made an oak gat some 20 years ago with a BZP fixings and there is very little staining on it.

 

[MikeG.]

If aesthetics are not an issue dont worry. Yes you will get some blue/black staining but never had steel fixings corrode through due to the reaction. Made an oak gat some 20 years ago with a BZP fixings and there is very little staining on it.

You've never taken apart old stuff made of oak, then.

 

[Beau]

If aesthetics are not an issue dont worry. Yes you will get some blue/black staining but never had steel fixings corrode through due to the reaction. Made an oak gat some 20 years ago with a BZP fixings and there is very little staining on it.

You've never taken apart old stuff made of oak, then.

Of course I have. Yes the steel corrodes a bit. Not dealt with small steel screws which might be a problem but pulled plenty of old bolts out of old oak.

Just re reading the OP opening post and he is fixing 3x6 oak to a brick wall. How about using the sleeved screw fixings like these. Only plastic then in contact with the wood https://www.screwfix.com/p/fischer-nylo ... pack/99097

 

[E-wan]

Thank you for all your comments. I will definitely be drilling pilot holes and countersink. And will practice on a couple of offcuts to get an idea of how easily the screw heads might shear off with power tools or by hand.

Do you think I would be more likely to shear heads off with a hand brace or a drill driver?

Thanks

Ewan

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[chaoticbob]

Do all metal fixings screws bolts ETC in oak needs to be Stainless Steel?

I've heard that the tannic acid in oak will react with the metal but not sure if this is a cosmetic concern or whether it will actually eat through the metal in time.

I'm planning a new back gate which will involve fixing some 3x6 pieces of oak into brickwork. The structure will be exposed to the elements and get fairly wet.

If they do you need to be stainless does it matter if it's A2 or A4 grade?

Thanks

Ewan

Sent from my SM-G900F using Tapatalk

A2 (304) stainless is considered corrosion resistant in 50% tannic acid according these guys.
Orbital Fasteners do A2 up to 6x150mm - they price by the hundred but will supply however many you want priced pro rata. Westfield Fasteners do up to 6x120mm in A4 in small quantities but they're not cheap.
Robin

 

[Keith 66]

Trouble with 304 or A2 is half the time you really do not know what grade the stuff is, i have seen some screws that rusted nearly as fast as if they had been mild steel. If its going outside I would use A4.
I usually use Anglia Stainless, https://www.angliastainless.co.uk/, good people to deal with. They also do Silicon bronze if you want real corrosion resistance but the price is eye watering. If you drop Sil bronze screws on the floor you pick them up!

 

[AES]

Assuming the driver bit is a good fit in whatever head the screws have, I would GUESS that the "worst" (from the viewpoint of twisting screw heads of) would be the hand brace (never actually tried it, but generally you can get a load of torque on with those). I suggest a drill/driver, starting off at the lowest torque setting. As you say, pilot drill and countersink is IMO essential. BUT my own experience with SS screws is quite limited.

 

[mbartlett99]

I can't help thinking that those complaining of easily shearing heads off ss fasteners have suffered the curse of crap stainless - there's a huge amount of total rubbish out there. On one vessel I worked on - German built but chinese fittings - the stainless rails and treadplates rusted immediately on contact with saltwater. The stainless screws selection box I bought from toolstation last year had the resilience of warm chocolate, I could not use my driver on them at all and even by hand it was 50/50. Binned the lot. Spax stainless torx head (German made) is my usual choice and I have yet to knacker a single one.

Anyway in answer to the OP; https://www.accu.co.uk . There was another outfit I use for unusual fixings in small numbers but I can't find the email yet.

 

[AES]

I think you're probably quite right there mbartlett99.

One (of several) problems that DIYers and hobbyists have is they usually only buy in small quantities, especially with special fasteners like SS screws. I do anyway.

They (I) are normally thrown into 2 choices - trust to luck in the stuff offered at DIY sheds, etc (which CAN be OK - sometimes) or pay a lot of money for a quantity that is usually much too much.

DIY, etc, stuff often has limited info on the packaging, and asking is often as useful as asking my dog (and she's been dead for the last 15 years)!

One of the problems with SS (like ali for example) is that specs vary hugely - some SS can, and indeed does, stain AND/OR rust in "normal" situations, let alone in salt water!

My local, well-respected tool dealer sold me 50 off SS woodscrews for my garden bench (oak) - much more than I needed, 20 off would have been fine. They looked fine, with good torx heads, but their torque capacity was VERY low - I would have called them medium price, they were not cheap (IMO).

Glad I'm not a professional in that area, getting the right stuff for boats, etc, must be either very expensive or a nightmare - probably both sometimes!

One "advantage" of the aero industry before I retired - what fastener to use was exactly specified, but all cost an arm and a leg (but at least I wasn't paying the bills back then)!

 

[mbartlett99]

Aero fastners = ouch. My Dad did missiles and I thought marine were bad.

I've finally decided there's no point saving money with fasteners (which upsets the Yorkshire in me no end) and just use spax. Tried Axminsters range which were ok but no better than that.