143 Nm

Most bolts are supplied with some oil on them anyway .. its a debate that never ends . I just do them tight . Then about half a turn . The torque to yield method !! With graphite grease .

OMG what a mine field Looks like Zinc plated M12 bolt 10.9 HT lubricated with loctite = 95NM I have rung tow bar fitters, ARB, and numerous engineering firms and get different answers from all Some off the tow bar supply and fitting business dont even know the toques settings they use, they say they just rattle them up tight Scary when you think of it

Are there a "turn-of-the-nut" techniques for automotive applications? Perhaps those techniques would overcome all the issues associated with friction on the threads?

Hi Bob, yes I found your spread sheet and have downloaded it

I have sent it to all my mates that have Caravans

they all reckon its BRILLIANT also

Thanks again Ken

 

watsea wrote:

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Are there a "turn-of-the-nut" techniques for automotive applications? Perhaps those techniques would overcome all the issues associated with friction on the threads?

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Thats the torque to yield method . Like 30nm and 180* turn tightening . That way any thread tightness doesnt matter !  Most automotive head bolts are done this way !  

180degrees

I have been reading this topic with some interest over the last few days and my thoughts are that under certain circumstances the material and construction type of the actual mounting area on the chassis or frame of the vehicle may play a part in the application of the correct tension.

We can discuss the varying tensions of bolts but the shape and strength of the frame of the vehicle might play a part if that area begins to crush if the tension of the mounting bolts exceeds the vehicle manufacturers specification.

This crush may not be visible but may exist in certain circumstances .

Maybe check with manufacturers specifications prior to tensioning it to the bolt manufacturers specification.

From my own experience, when we used to fit tow bars to vehicles before all the specialised tow bar shops popped up, those kits used to come with bolts, nuts, flat washers and Spring Washers.
Maybe the Spring Washers were there to *idiot proof* the tensioning of the bolts or to provide nut security while at the same time compensating between the strength of the first year apprentice and the mid thirtys well built and very fit tradesman.

Or were the bolts and washers in the kit compensating for the materials and design of the then, very new, mono constructed vehicles.

Oh and as my memory comes back to me as I type, I have not yet mentioned *fishplates* which were provided to be fitted each side of the frame to spread the load of the bolt heads.

My suggestion to the OP is to contact the vehicle manufacturer rather than some aftermarket fitter and supplier whose tension wrench is in most cases a *rattle gun*.

I would think that spring washers + locktight X arm strength of 81 year old male would be sufficient.

Ian G wrote:

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Just do what most people do and tighten then firmly with a standard spanner or ratchet, were not talking about a cylinder head, check them again after a few uses if you are concerned, the last thing you want is to strip the thread in the chassis, worry about something more important like the price of beer !! Ian

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It is not "Rocket Science."........    KB

KJB wrote:

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Ian G wrote:

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Just do what most people do and tighten then firmly with a standard spanner or ratchet, were not talking about a cylinder head, check them again after a few uses if you are concerned, the last thing you want is to strip the thread in the chassis, worry about something more important like the price of beer !! Ian

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 It is not "Rocket Science."........    KB

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 Hmm 

Do not sweat over the little things. Including the price of beer !! 

This table does not answer your question directly but I use it when i want a torque. They are the largest bolt and fastners supplier around here. Good for mail order too !!

 https://nhtb.com.au/steel-hex-head-bolts-metric.html

Jaahn

Thanks Mike, and here is the answer for the OP.
Use the standard torque figure supplied in any table for your size, and then multiply it by the suitable factor shown in the table below !! from Mikes second reference. https://www.boltmasters.com.au/technicaldata

Surface Condition Torque Adjustment Factors

Plain Steel, as supplied x 1.0
Plain Steel, degreased x 2.0
Zinc Plated, as supplied x 1.0
Zinc Plated, lightly oiled x 0.9
Galvanised, degreased x 2.1
Galvanised, lightly oiled x 1.1
Heavily greased x 0.7

So the answer is : M12 coarse threaded Zinc plated grade 10.9 bolts,  recommended 109 nm. multiplied by factor below of x 1 = 109 nm  

Phew thanks for resolving that important problem and finding the correct fudge factor for zinc plated bolts as supplied. 

Jaahn

 

-- Edited by Jaahn on Friday 16th of September 2022 07:42:09 PM