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Bolt Grade Specifications
danicortes22 - 1/4/19 at 02:56 PM

Which is more cold weather resistant, Grade 10.8 or 10.9 bolts? What is their main difference? Is there a chart or specifications that I could look at that could tell me their main differences (specifically when it comes to cold weather)?


Thank you,


CosKev3 - 1/4/19 at 03:35 PM

10.9 compared to 12.9 you mean?

Not sure how temperature effects them,but 12.9 are a higher tensile,so stronger


jps - 1/4/19 at 04:32 PM

I would have thought it's very dependent on the application - an exposed bolt into a nut is going to behave very differently to a bolt into a threaded hole within a larger mass. And the size will make a difference too.

I would also have thought that - if it's anywhere - it'll be in the ISO?


HowardB - 1/4/19 at 05:03 PM

in the world of Offshore and Subsea a 12.9 bolt that might be exposed to salt spray was not acceptable as the rate of corrosion/failure was deemed to be much higher.
12.9 is high carbon high tensile, 10.9 is next lower and 8.8 lower still, I believe there are 6,5 and 4 versions, each with lower carbon content and lower tensile strength


snapper - 2/4/19 at 06:24 AM

quote:
Originally posted by danicortes22
Which is more cold weather resistant, Grade 10.8 or 10.9 bolts? What is their main difference? Is there a chart or specifications that I could look at that could tell me their main differences (specifically when it comes to cold weather)?


Thank you,


Why do you want to know?

There is much more not said than said in your question.


nick205 - 2/4/19 at 08:06 AM

quote:
Originally posted by snapper
quote:
Originally posted by danicortes22
Which is more cold weather resistant, Grade 10.8 or 10.9 bolts? What is their main difference? Is there a chart or specifications that I could look at that could tell me their main differences (specifically when it comes to cold weather)?


Thank you,


Why do you want to know?

There is much more not said than said in your question.



I'm not a material scientist or thread expert, but I do agree with...

Why?

Dimensions?

Application?

Temperature range(s)?

Can you give a bit more information about what you want to do?


mcerd1 - 2/4/19 at 09:12 AM

Bolt materials are specified in ISO 898-1

the standard grades are 3.6, 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 9.8, 10.9 and 12.9 - but only 4.6, 8.8, 10.9 and 12.9 are common in the UK with use of the others actively discouraged.


So grade 10.8 doesn't really exist in the ISO system - 10.9 is the correct grade at this tensile strength (nominally 1000 N/mm )

The second number in the grade ".9" relates to the ratio of yield / 0.2% proof stress to tensile stress:
for a 10.9 bolt 0.2%proof stress = 900 so 900/1000 = 0.9 (or 90%)
so a lower second number in the bolt grade will yield sooner, but also give more warning that higher grade that is more likely to suffer a sudden brittle fracture




For structural use in low temperature it brittle fracture you'd worry about (same as any steel) - in general temps down to -20C are fine but bellow that you should be specifying a min. test temperature at which the bolts should achieve a charpy v-notch impact toughness of at least 27J


so if the expected min service temp is warmer than -20C then I wouldn't worry too much (UK outdoors is typically -15C for structures) - but if you are concerned you need to specify the extra testing on your bolt batches to be done the manufacturer


from a automotive point of view I know that Ford use 10.9 for most of the suspension, brake and chassis / sub-frame bolts and 8.8 on various other parts

[Edited on 2/4/2019 by mcerd1]


hughpinder - 2/4/19 at 10:21 AM

A bit of information here
http://www.spartaengineering.com/effects-of-low-temperature-on-performance-of-steel-equipment/

and I thought the Wurth site was going to give the info you needed, but almost seems like this article was cut off before it ended, but still interesting.
https://www.wuerth-industrie.com/web/media/en/pictures/wuerthindustrie/technikportal/dinokapitel/Kapitel_01_DINO_techn_Teil.pdf


redturner - 4/4/19 at 01:28 PM

quote:
Originally posted by mcerd1
Bolt materials are specified in ISO 898-1

the standard grades are 3.6, 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 9.8, 10.9 and 12.9 - but only 4.6, 8.8, 10.9 and 12.9 are common in the UK with use of the others actively discouraged.


So grade 10.8 doesn't really exist in the ISO system - 10.9 is the correct grade at this tensile strength (nominally 1000 N/mm )

The second number in the grade ".9" relates to the ratio of yield / 0.2% proof stress to tensile stress:
for a 10.9 bolt 0.2%proof stress = 900 so 900/1000 = 0.9 (or 90%)
so a lower second number in the bolt grade will yield sooner, but also give more warning that higher grade that is more likely to suffer a sudden brittle fracture




For structural use in low temperature it brittle fracture you'd worry about (same as any steel) - in general temps down to -20C are fine but bellow that you should be specifying a min. test temperature at which the bolts should achieve a charpy v-notch impact toughness of at least 27J


so if the expected min service temp is warmer than -20C then I wouldn't worry too much (UK outdoors is typically -15C for structures) - but if you are concerned you need to specify the extra testing on your bolt batches to be done the manufacturer


from a automotive point of view I know that Ford use 10.9 for most of the suspension, brake and chassis / sub-frame bolts and 8.8 on various other parts

[Edited on 2/4/2019 by mcerd1]

That is really interesting. However, what kind of strength would Ford use in something like a crank pulley bolt which has to support several items and of course needs to be tight...


mcerd1 - 4/4/19 at 01:46 PM

quote:
Originally posted by redturner
That is really interesting. However, what kind of strength would Ford use in something like a crank pulley bolt which has to support several items and of course needs to be tight...


The crank pulley bolt should't be taking any of the load directly (for a start its on the same axis as the crank)

most of the load will be transferred by friction (all of the load on cranks without keys) and the bolt only has to be strong enough to generate a sufficient pre-load to prevent slip
from memory the likes of a pinto uses an 8.8 bolt and I think a zetec is a 10.9 with a higher torque setting - but the pinto uses a much bigger bolt too - so horses for courses


for structural use 8.8 and 10.9 bolts are both commonly used for friction grip assemblies depending on the pre-load required (each with their own special nuts and washers)

[Edited on 4/4/2019 by mcerd1]


jps - 4/4/19 at 04:35 PM

quote:
Originally posted by redturner
That is really interesting. However, what kind of strength would Ford use in something like a crank pulley bolt which has to support several items and of course needs to be tight...


I torqued one a few days ago on a Pinto. The Haynes manual has different torque ratings for 8.8 and 10.9. Mine was 10.9.