UKH

Hi all,

Q: A construction project I've just been awarded calls up 316ss cast in M16 ferrules to which we're to bolt on lots & lots of 'things' once the form work's stripped.

From experience I've encountered many problems screwing a male set screw into a female threaded sleeve as they tend to bind & totally lock up yet can easily spin a female nut down a male threaded rod. Is it something to to with dia vs depth? I figure it must be because ,, because that's all I can think of.

Cheers,

AP.

The problem with long stainless fasteners galling-up is insufficient lubrication and the way they are made, normally the female threads are machined which always give more problems than rolled threads. The standard anti-sieze treatment which comes on bolts is enough for a nut but gets rubbed off as it goes down a deep hole. Absolutely clean is naturally the first requirement ( a problem on site where concrete is concerned) and then plenty of anti-galling compound.

If the cast-in sleeves are multi-piece then welding is often the culprit as well and you need to run a bottoming-tap down first then plenty of lubricant.

Consider using an anti seize paste like this https://www.rocol.com/products/stainless-steel-anti-seize   rather than copper or aluminium based greases.

I work in lubrication and have no interest in the above, though I am interested in it!

"I work in lubrication" Always suspected that.... good thread knowledge everyone.

Presumably you need to fix the female thread gadget to the formwork.

If you do this with a full length male threaded bolt/bar, well lubricated, the concrete cannot get into the threads.  You also know the threads work.

Brill, thanks jimtitt et al, I reckon our problem's solved.

Might point out a few big Melbourne construction projects am involved with on another thread.

Cheers,

Andy.

As an aside for anyone interested in Industrial Rope Access work I suggest you ought check out 'API Rope Access Services' on YT.

As already referred to, stainless steel galling, also called cold welding, is a common problem and is often solved by using specialist pastes. 

A wide range of lubricants will work but the pastes are useful because they tend to stubbornly remain on the material even in difficult conditions and are fairly idiot-proof. They can bring their own problems, not least the tendency to collect debris which subsequently obstructs fitting of the fastener. 

If you intend to use a locking/sealing adhesive on the fastener then a separate liquid or paste lubricant should not be used as it would affect the properties of the adhesive. In this case, one chooses an adhesive that sets slowly and also has a lubricating property. 

There can also be situations where a solid lubricant might be appropriate. Nip down the supermarket for some Talc. Yes, powdered rock. Talc can be difficult to use but will lubricate while not detracting from the properties of lubricants or adhesives used at a later stage.

And if you think stainless steel is bad, try Titanium! Dreadful stuff.

Wasn't powered graphite good for this sort of issue?

Probably better suggestions above, I'm going back some time in the past.

Definitely take some M16 taps and some cutting paste, never know what is stuck in the thread when they've been set. Stainless threading is horrible and can be a nightmare on the best of days.

How long are the threads going into the ferrules?

Thanks,

The cast in ferrules will be M16 x 90mm Elephants Foot type and fixed down to the form ply with plastic nailing plates which are small plastic discs with a threaded male 'nipple' on top. The discs have small holes near the edges for thin nails and the deformed cross bar threaded though the middle gets tied into the reo in the slab. Problem is they often get knocked over by the vibrators and become defunct.

I'll play around with the various lubes as the bolts going in are to support Rope Access anchors and monorails and shall be concealed, inaccessible [virtually] and permanent.

Cheers all, appreciated.

Andy.

Anti seize pastes generally contain a solid lubricant, often copper or aluminium. The one I linked to above has a high content of Molybdenum Disuphide which acts both as an inert layer between two metals and provides an extremely thin layer of lubrication. This thinness makes it a good choice and it is probably the solid of choice for precision anti seize performance. Graphite is also used but works differently, it is like a pack of well coated playing cards, providing lubrication by sliding under load.

I can't comment on talc, the idea is sound, and it is easier to obtain than Moly disuphide, but I'm not aware of any talc based lubricants on the market.

Talc is used for all sorts of dry-lubricant applications but not so much in engineering, more materials handling, it is common for stuff like seeders to help the grains flow better.

The rest of the world (like me) uses PTFE spray!

You live and learn! 

Sounds as though you have been doing too much screwing with the male part before you have sufficiently examined the female sleeves.

We used to use a compound that contained both grease and clay. It had the added advantage of stopping galvanic corrosion if you happened to be putting together bits made from different metals. It had the disadvantage of turning into a permanent stain if you happened to get any on your clothes. Anyway, here's a nice little explainer.

http://www.bostik-industrial.com/never-seez-anti-seize-compounds/

Male, female, screwing, lube and vibrators... I think me and the missus need a lie down. Hope you're well Andy.

Hope you're well Andy.

Am OK ta Dave, hope you are too and thanks all for the helpful advice above. In the examples I have coming up I have nowhere to go other than retro-coring through a post-tensioned slab and through-bolting if my bolts bind in the ferrules.

Cheers,

AP.