Does any one know the bolt torque setting in NM for tow bar with M12 coarse threaded Zinc plated grade 10.9 bolts ??
BarneyBDB said
06:39 PM Sep 9, 2022
143 Nm
Bukhouse said
09:05 PM Sep 9, 2022
Hi Barney thanks for reply every thing I read gives a different answer from 73nm to 139nm but apparently
Zinc high tensile bolts are classed as lubricated bolts and the torque rating is less than Black steel high tensile bolts
Aus-Kiwi said
09:40 AM Sep 10, 2022
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 .
Bulldozer said
10:19 AM Sep 14, 2022
Tighten till your elbow clicks.
Bukhouse said
04:26 PM Sep 14, 2022
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
Bobdown said
04:33 PM Sep 14, 2022
Bukhouse wrote:
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
Ken, did you see that I loaded up the spreadsheet you requested about van loads etc, under Ranger towing. Don't know if you saw it or not but noticed your post today.
Cheers Bob
watsea said
06:35 PM Sep 14, 2022
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?
Greg 1 said
07:40 PM Sep 14, 2022
Lubricated bolts always have a lower torque than a bolt assembled dry.
This is because of binding in the thread when dry so the 95 nm would be about right for that size bolt with lubrication.
Automotive applications should always be torque up with a torque wrench, particularly those that are mission critical.
Simply rattling them up tight is not good enough. Half the reason for failure of fasteners is incorrect torque. Either by overstretching with too much torque or by the item coming loose by under torqueing.
Bukhouse said
08:56 PM Sep 14, 2022
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
Bukhouse said
09:02 PM Sep 14, 2022
Hi Greg, I thought bolts were bolts until researching bolts for tow bar
also found that it was recommended not to use spring washers with HT bolts and that its the torque setting that prevents the bolt from coming undone
not spring washers
Aus-Kiwi said
09:26 PM Sep 14, 2022
watsea wrote:
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?
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 !
Bukhouse said
11:44 PM Sep 14, 2022
Does that mean torque to 30NM then tighten extra 180
Bukhouse said
01:16 AM Sep 15, 2022
180degrees
iana said
08:47 AM Sep 15, 2022
Are you talking about Hi-Tensile bolts that are acting in shear, and not in tension ?
Ivan 01 said
09:16 AM Sep 15, 2022
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*.
Greg 1 said
06:19 PM Sep 15, 2022
Ivan, Good post.
Provided that the manufacturer can provide the figures.
Half the nitwits in service divisions these days dont even possess a workshop manual.
Had that issue with my local Ford dealership.
jegog said
07:51 PM Sep 15, 2022
I would think that spring washers + locktight X arm strength of 81 year old male would be sufficient.
Ian G said
10:44 AM Sep 16, 2022
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
KJB said
10:53 AM Sep 16, 2022
Ian G wrote:
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
It is not "Rocket Science."........ KB
Ian G said
11:10 AM Sep 16, 2022
My mattress was made by rocket scientists and it is the worst mattress I have ever had, sorry for getting off the topic !!!
Jaahn said
12:01 PM Sep 16, 2022
KJB wrote:
Ian G wrote:
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
It is not "Rocket Science."........ KB
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 !!
Thanks Jaahn, you're link got me Googling because I didn't understand the "Class" reference in the table. Here's another couple of links which provide more information:
-- Edited by Mike Harding on Friday 16th of September 2022 12:50:25 PM
Jaahn said
06:50 PM Sep 16, 2022
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
landy said
09:11 PM Sep 16, 2022
Ian G wrote:
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
This method has served me well for a long, long, long time. never had a problem. Landy
Tony Bev said
04:15 PM Sep 17, 2022
I have never torqued tow bar bolts, but have always done them up tight, and fitted spring washers, as it helps them coming undone
Hi,
Does any one know the bolt torque setting in NM for tow bar with M12 coarse threaded Zinc plated grade 10.9 bolts ??
Hi Barney thanks for reply every thing I read gives a different answer from 73nm to 139nm but apparently
Zinc high tensile bolts are classed as lubricated bolts and the torque rating is less than Black steel high tensile bolts
Tighten till your elbow clicks.
Ken, did you see that I loaded up the spreadsheet you requested about van loads etc, under Ranger towing. Don't know if you saw it or not but noticed your post today.
Cheers Bob
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
Hi Greg, I thought bolts were bolts until researching bolts for tow bar
also found that it was recommended not to use spring washers with HT bolts and that its the torque setting that prevents the bolt from coming undone
not spring washers
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 !
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*.
Provided that the manufacturer can provide the figures.
Half the nitwits in service divisions these days dont even possess a workshop manual.
Had that issue with my local Ford dealership.
It is not "Rocket Science."........ KB
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 Jaahn, you're link got me Googling because I didn't understand the "Class" reference in the table. Here's another couple of links which provide more information:
ISO bolt classes
ISO bolt torques
-- Edited by Mike Harding on Friday 16th of September 2022 12:50:25 PM
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
This method has served me well for a long, long, long time. never had a problem.
Landy