Fastener strength, sizes & guide torques

Standard = Imperial as far as I can tell.

Most applicable stuff to VAG will be metric.



Usually we see 8.8 and 10.9 (second from right and far right, bottom row):





Guide torques:

 

Useful information, now does anyone have any guide torques for metric stainless steel fixings?

 

There is a whole heap of info on www.tribology-abc.com (Chapter 5 possibly) but it's really an engineers fest, so I left it off this thread initially!

 

Never knew of the markings for Metric Studs before.

Shame there are no markings for 12.9 and 14.9 studs![:^(]

But:

The torque figures are utterly misleading because they do not indicate what, if any, lubricant is used.

The scatter I assume is to cover from 4.6 to 10.9 metric grades?

Where are 12.9 and 14.9 data?

Did you get this from a US source Chris?

 

Well that's answered my final question before I asked it!

Thread pun intended?

 

Pun nut intended

You will not believe the source of the info in post 1 ! It wasn't the tribology site.

 

Brilliant find Chris!

Lubrication covered here!

http://www.tribology-abc.com/sub9.htm

Pre-Loads calculated here!

http://www.tribology-abc.com/sub9.htm

 

I think 'find' would be pushing it! As any Engineer should know, Accountants only do what they did last year!

Whilst having my Gemini gearbox rebuilt last year, there was a bit of uncertainty on the crownwheel and end-casing tightening torques. So I spoke to a man and he used the Tribology info.

The info in post one, believe it or not, is from here!

 

US Haynes!

Nuff said!

 

Great off the back of that then A2 ss has a Tensile Strength of 700 which can be related to bolt grades. I used this chart here.

 

Are they though? That chart shows A1 through A5 but only 4 columns...

I`m looking for the stainless equivalent of 10.9s

 

Stuart.

These people can make you A4 100s. I guess other people can!

http://mdmetric.com/fastindx/t28u.pdf

 

The grade A1, A2 etc refers to the material make up, A2 being common, A4 has better corrosion resistance and is often used in marine applications - as you probably know.

On the bolt there will be a number as well. A2 - 70 For example.

The figure (70 in the example) is the Strength class of the material which relates in the table to Tensile Strength. Any of the grades can vary in tensile strength.

If you want 10.9 you need your number to be 100 and then what ever grade you require.

 

What have I said here?

http://www.clubgti.com/forum/showpost.php?p=2064460&postcount=12

OK, I missed out the - between A4 and 100!

ET 35 by the way!

 

Ill update the library

 

Nice one. Makes more sense now.

Despite coming from a Marine background, stainless fasteners are something I, oddly, have no experience of (grade requirements wise anyway)...

Ta!

Shan`t need them made though, since they don`t need to be stainless (preferably not actually).

I`m `acquiring` them from work for a friend who`s going to be running stub-axle spacers, and the only bolts we have in the required size are stainless A2-70s. Guess he`ll just have to pay out at our local supplier for `proper` 10.9s after all!

 

Stu.

These people will make you C1 - 110 fasteners if you want them!

Dave.

ps.
They can probably make you some Alloy Wheels to market under the 'StuMc' trade name!
If they can't, they will definitely know of the odd one hundred, or so, Chinese companies who can make you Wheels!

 

I spent a fair bit of time researhing torque tightening in my last job and discovered that torque tightening s/s fasteners is not a good idea. According to the roymech website, 90% of the applied torque is required to overcome thread and bearing surface friction, seperately a study in Italy showed that all other things being equal, the coefficient of friction for austentic stainless steel doubled (or halved) according to humidity. This may cause massve inaccuracies when torque tightening stainless steel.

Also, thread galling can lead to increased friction in stainless steel which again will cause inaccuracies when torque tightening.

These factors meant that I was unable to find reliable information for the friction values of stainless steel. Without this information it is impossible to even guess at a torque value.

 

Jaundice.

IIRC, the Molykote Handbook gives figures for friction values for different thread lubes at different temps., with notes regarding SS. Lots of scatter I seem to remember!

Once did a machine for BNFL where the bottom half was all SS. I had a real problem finding suitable High Strength SS. Ended up paying a small fortune for US Aeroscape stuff. The bolted joints were all fitted bolts in shear. We made some tests and found Molycote Anti-Sieze Compound or Rocal ASP gave reasonably consistent results.

Thread Galling is possibly the most galling factor when using SS fasteners!

Dave.

 

Will bear that in mind for the future thanks

Seriously!!!

Most sources of information seem to agree on three ways of preventing thread galling in s/s:

1. Use different grades for internal / external threads (A2 bolt A4 nut for eaxample)
2. Reduce installation RPM. (In my experience this makes little difference, I still had threads gall when undoing with hand tools)
3. Lubricate the threads with Molybdenum Disulphide (Molyslip)

I came to the conclusion that due to cost, thread galling, and weaker tensile strengths, unless there is no real alternative using s/s fasteners is generally not a good idea, especially when I found a supplier of PTFE coated mild steel fasteners who could supply them cheaper than the s/s equivalent.