Stainless steel bottle screws seized up//whats the 'term' for this?

[castaway]

Stainless steel bottle screws seized up//whats the \'term\' for this?

Re my other post about my roller furling gear...

What had kicked this all off was that the gear had jammed up due to corrosion with in the drum/bearing, no big problem except that I had to disassemble the the bottle screw to take it off to give it a good seeing to.

Of course no job is that simple and whist one end of the bottle screw came off dead easy the other end lost most of its threads as it came apart, due, I believe, to a tendency for the surfaces of S/S to bond molecularly.

There is a term for this something like 'grippin' or gripeing' , could someone enlighten me so as I sound like I know what I'm talking about.

Thanks Nick

 

[Ships_Cat]

Re: Stainless steel bottle screws seized up//whats the \'term\' for this?

Galling

John

 

[jonathankent]

Re: Stainless steel bottle screws seized up//whats the \'term\' for this?

[ QUOTE ]
Stainless steel bottle screws seized up//whats the 'term' for this?

[/ QUOTE ]
Bu****ed! /forums/images/graemlins/smile.gif

 

[aph]

Re: Stainless steel bottle screws seized up//whats the \'term\' for this?

Its called galling. Once you gall the threads you can throw the fitting away. You will never free it up. It is imperative that threads are clean before assembly. We use anti galling compound on all stainless fittings offshore drilling rigs.

 

[sarabande]

Re: Stainless steel bottle screws seized up//whats the \'term\' for this

Isn't "galling" associated with constant friction, rather than a high static load which is "cold-welding"? The effect may be the same (reluctance of screw to turn in the thread) but preventive treatment may require different lubricants.

Nylok Corp here have some details. Any other suggestions / recommendations to prevent seizure ?

 

[Ships_Cat]

Re: Stainless steel bottle screws seized up//whats the \'term\' for this

I am quite certain that you will find that the problem with ss threads is normally always referred to as galling and that is correct usage.

Galling also sounds like the original poster's like 'grippin' or gripeing' whereas "cold welding" does not sound anything like those - so I assume that galling was the correct term looked for.

John

 

[sarabande]

Re: Stainless steel bottle screws seized up//whats the \'term\' for this

I think we are all concerned with either preventing the problem occuring in the first place, or freeing a seized bottle-screw. The latter seems impossible if the internal surfaces have joined at a molecular level, rather than just corroded a little.

Since there is both a friction and a high static (and impact) load function in bottle-screws, either galling and/or cold-welding may be responsible for seizure.

It seems that fastening industry practice is to ensure that screw and thread components are very clean prior to assembly, and then to apply varying anti-galling compounds (depending on the metals used) to both

1 lubricate the component (reduces friction) and
2 prevent the internal surface coming into surface contact at the molecular level (inhibits cold-welding).

galling / cold welding seems to give good advice, especially about sunshine, of which I had not previously been aware.

There are any number of specialised anti-seize compounds available. Ordinary oil/WD40 is regarded as second choice.

 

[Pye_End]

Re: Stainless steel bottle screws seized up//whats the \'term\' for this

Is it just ss that suffers from this or does bronze do this as well?

Looking towards my next standing rigging change and note that bronze rigging screws are not much different in price - is it a good idea to go for these?

 

[SteveA]

Re: Stainless steel bottle screws seized up//whats the \'term\' for this

I had the same problem with s/s to s/s bottle screws and was advised to change to ss to chrome bronze - haven't had a problem since.

 

[sarabande]

Re: Stainless steel bottle screws seized up//whats the \'term\' for this

Bronze and most bronze alloys tend to be resistant to friction welding (galling), and are often used for bearings or similar metal to metal uses, e.g. sliding gear. Nearly always with some oil-type lubrication or by graphite plugs. Lead-bronze alloys however are prone to galling. Silicon-bronze is often specified in the marine industry; phosphor-bronze is more easily cast, and is very wear-resistant (hence its use for propellors).

Some bronzes can be joined together by cold-welding, and are pressed together to form a deformed strong joint.

Atmospheric moisture - often aggravated by saltspray - generally induces surface corrosion on bronze, which may weather to green or brown. If there is a gap (however small) in the screw-thread interface, sea water will be drawn into it, and cause the bottle-screw to lock. Known as crevice corrosion. Bronze is frequently chromed to help avoid crevice corrosion,a nd can then be used in contact with stainless rigging.

I guess it comes down to aesthetics, specification for the job in hand, and price.

A reputable supplier will be able to give you the specification (breaking strain, alloy composition, suitability for purpose, etc) and if you are using bronze fittings, it pays to take extra pains to exclude air and water from the threads by anti-seize compounds, boots, almagamating tape, etc. The use of dissimilar metals far from bronze in the "noble" scale in the vicinity should be discouraged.

The Copper Development Association

try here
has some fascinating pages on the use of copper for anti-microbial and other hygiene purposes, as well as information on corrosion. I have used copper swarf to prevent slugs eating vegetable seedlings, with high success.

The pages also have lots of references to the use of copper for prevention of bio-fouling.

 

[cliff]

Re: Stainless steel bottle screws seized up//whats the \'term\' for this

Galling Definition: A condition whereby excessive friction between high spots results in localized welding with subsequent splitting and a further roughening of rubbing surfaces of one or both of two mating parts.

Friction Welding Definition: Friction welding is a solid state welding process which produces coalescence of materials by the heat obtained from mechanically-induced sliding motion between rubbing surfaces. The work parts are held together under pressure. This process usually involves the rotating of one part against another to generate frictional heat at the junction. When a suitable high temperature has been reached, rotational motion ceases and additional pressure is applied and coalescence occurs.

The problem with the turnbuckle is GALLING of the threads (as Ships_Cat (John) rightly stated above) probably caused by dirt or deformed threads or corrosion products and "brute force and ignorance" being used to force the threaded part out of the turn buckle. As the threaded part turns, some minor galling will occur resulting in material pickup which will increase the galling effect which will result in more galling and material pickup which will result in more galling which...... Eventually the threads are so badly deformed they are lost and not recoverable. This phenomenon is not referred to as "friction welding" but is called Galling.
--------------------

"Artificial intelligence is no match for natural stupidity"
sailroom <span style="color:red">The place to auction your previously loved boatie bits</span>

 

[TheBoatman]

Re: Stainless steel bottle screws seized up//whats the \'term\' for this

If you want to minimise the problem of Galling on s/s fittings use either a graphite or molyslip grease or a copper based compound (as used on brake pads).

BUT you only need a bare minimum!

Peter.

 

[sarabande]

Re: Stainless steel bottle screws seized up//whats the \'term\' for this

So galling is an accidental process, and friction welding is done on purpose ? The boundaries, if you will excuse the term, of what the cause is seem to be very marginal. I am happy to live with any definition provided it's used consistently and within the right operational context.

At any rate we seem to have arrived at

1 some practical suggestions for anti-galling compounds, (thanks, Boatman)

2 practical advice on how to reduce the risk of galling when installing bottle-screws

3 a concensus that seized bottle-screws cannot be recoverd and should be chucked

4 practical suggestions for alternatives to stainless steel for bottle-screws

Progress, I feel, has been made in advancing the sum of human knowledge and PBOwning.

'nuff said. /forums/images/graemlins/smile.gif

 

[cliff]

Re: Stainless steel bottle screws seized up//whats the \'term\' for this

[ QUOTE ]
So galling is an accidental process, and friction welding is done on purpose ?

[/ QUOTE ]Yes, you seem to have got that bit correct at least. The amount of incorrect information (misinformation) presented on these forums, particularly concerning metallurgy, beggars belief at times - stick with it, I am sure you will pick up the correct terminology in time. /forums/images/graemlins/grin.gif

There are a few (very few unfortunately /forums/images/graemlins/smirk.gif) metallurgists on the forum who I am sure would be happy to help.
--------------------

"Artificial intelligence is no match for natural stupidity"
sailroom <span style="color:red">The place to auction your previously loved boatie bits</span>

 

[gandy]

Re: Stainless steel bottle screws seized up//whats the \'term\' for this

Cliff ...

This is a hot topic for me because I buggered a rigging screw this spring. You know the old advice "as long as you use hand-tools you can't over tighten". Well I took that literally, result one stripped rigging screw on the backstay.

What's the correct stuff to put onto stainless rigging screws to prevent this? I've see so many different recommendations. 3-in-1 oil, moly grease, copperslip .. or what? The rigging company are recommending SS rigging screws for the new rigging, and I don't want problem with them.

Thanks

 

[cliff]

Re: Stainless steel bottle screws seized up//whats the \'term\' for this

If they were mine I would go for.....
"Moly-Slip" (Molybdenum Disulphide grease)
Graphite grease (waterproof type)
Copper-Ease (Copper based antisiezure assembly compound)
Waterproof grease
In that order.......

I would not say there is any right or wrong lubricant - all have advantages and disadvantages and I am sure there are others not listed above that other forumites will have used with success.
--------------------

"Artificial intelligence is no match for natural stupidity"
sailroom <span style="color:red">The place to auction your previously loved boatie bits</span>

 

[Graham_Wright]

Re: Stainless steel bottle screws seized up//whats the \'term\' for this

I was recommended Copper-Slip.

During the manufacture of a stainless steel shaft for a macerator (chicken carcasses- the sample stank to high heaven) with an M50 X 1mm thread, we gauged the thread with a threaded ring which became stuck (welded?) on the shaft. One of my oldest staff suggested tapping the ring around its circumference at the same time as trying to unscrew it. The theory was that the inter-molecular joints would be fractured locally. A few degrees at a time and eventually it was released.

Might not work on a bottle screw as the threaded portion may be too long.

 

[TheBoatman]

Re: Stainless steel bottle screws seized up//whats the \'term\' for this

Tony
Cliff has listed the types in order of preference (which I agree with) however there's very little to chose between them.

IMHO the easiest to get would be the copper slip (ease). Halfords sell it in small tubes - look in/around the brake pad section, one tube would last a lifetime for the amount you would use on bottle screws.

BTW copper slip is also very useful on spark plugs and diesel injectors!!!

Peter.

 

[gandy]

Re: Stainless steel bottle screws seized up//whats the \'term\' for this

Cheers. I'll go for Molyslip if I can get it.

 

[Ships_Cat]

Re: Stainless steel bottle screws seized up//whats the \'term\' for this

And if it has not bin said already, a common view is to screw them (or undo) up slowwwwwly, especially when load on the screw.

John