bolt/nut grades

I have to replace an M14 class 10.9 (SAE grade 8, AIUI). I can get
the bolt locally. But, at the same store, or anywhere ex online, the
highest grade nut available is class 8.8 (SAE grade 5).

So, my question really is, can I use the class 8.8 in this situation.
But, more generally, is it the case that the bolt needs to be stronger
than the nut - maybe it's under more stress because it's longer?

wrote:

>I have to replace an M14 class 10.9 (SAE grade 8, AIUI). I can get
>the bolt locally. But, at the same store, or anywhere ex online, the
>highest grade nut available is class 8.8 (SAE grade 5).
>
>So, my question really is, can I use the class 8.8 in this situation.
>But, more generally, is it the case that the bolt needs to be stronger
>than the nut - maybe it's under more stress because it's longer?

It's the correct application.

The idea is to spread the load across the full length of the thread in
contact with the nut. If the nut is too "hard" it will create a
stress point which can cause the bolt to fail.

There shouldn't be any such thing as grade 8 nut.

--
John H

On Tue, 18 Apr 2017 15:58:48 -0400, wrote:

>I have to replace an M14 class 10.9 (SAE grade 8, AIUI). I can get
>the bolt locally. But, at the same store, or anywhere ex online, the
>highest grade nut available is class 8.8 (SAE grade 5).
>
>So, my question really is, can I use the class 8.8 in this situation.
>But, more generally, is it the case that the bolt needs to be stronger
>than the nut - maybe it's under more stress because it's longer?

New info:
http://www.smithfast.com/newproducts...langelocknuts/
>" Grade GT Flange Style Lock Nuts
> An all metal, one-piece flanged hex nut which gets its prevailing
> torque characteristics from controlled distortion of its top threads
> from their normal helical form to a more elliptical shape
> ... It is designed specifically for use with, but not exclusively,
> grade-8 frame bolts.

Most vendors seem to offer this only in SAE sizes, not metric.
Except this, at Amazon.
https://www.amazon.com/M14-2-0-Flang...ords=m14-2+nut
Which seems exactly what I need.
.... though again here, the (supposed) vendor's own web site doesn't
seem to have _any_ metric all-metal lock nuts, flanged or otherwise.
(BoltsandNuts.com).

But, if you can't trust Amazon, who can you trust?