Are higher grade bolts more brittle?

I get the pictures, but only a headache from the text . Under AISC code here in North America, holes for shear bearing bolts need not be drilled in place. The AISC does require a reduction in shear capacity if the bolt threads fall in the shear plane.

I think we're closer on this point, though the AISC seems to be looser than your code in this regard as well. The rules for what sort of joint is required for a particular loading condition are spelled out in the AISC code I mentioned before.

I think I've heard all the jokes before, but wouldn't have guessed there were that many without seeing them all in one place.

It does confirm what I read in the ASM handbook, and referred to in the hydrogen embrittlement thread re plating causing more problems than pickling. IIRC, the handbook said zinc plating was a particular problem because the zinc seals the hydrogen in better than some other metals.

We made the most common error in discussion. We didn't specify what we were exactly talking about. So everyone had his own picture in his head and defended it. :-)

Furthermore, each field (be it planes or machines or whatever) has his tradition in how to look at things and what they want to avoid or achieve under all circumstances. The classical math to solve those problems always needs some simplifications and so we should have agreed upon that in the beginning.

Anyhow, interesting discussion with something to learn from! Better than ... oh you know! ;-)

Nick

A mate of mine said that Volvo have a policy of not allowing any bolts on an engine over grade 10.9 due to concerns over possible hydrogen embrittlement in the presence of moisture IIRC. The problem being an issue with fasteners over 1100N/mm^2, 10.9 being 1000N/mm^2. I also was told by my local fastener place that the supplier typically won't do

12.9 cap screws in plated anymore due to concerns over HE being a possible issue even with baking after plating.

I'm a tech, not an engineer, so I bent a 1/4" Grade 8 bolt 90 degrees to see if it would break. It didn't even crack. It bends like music wire.

Jim Wilkins

Some of you may recall my classic posts entitlied "Shop Furness" & "Shop Furness II- The Return of the Question"

I'm pleased to report that after many years of research & hard work I've finally done it!

I've finally learned to spell "furnace" the right way!! :)

&, oh, yeah- I got the thing working.

H.

Howard Eisenhauer wrote: (...)

Great writeup, Howard!

Thanks and congratulations!

--Winston

I was mildly surprised to learn that the (automotive) SAE grade 2, 5,

8, etc bolt specifications do not include brittle fracture ratings. This straight from the relevant spec committee chair people about 5 or so years ago. I've never seen (or if I did I forgot :-() the actual SAE bolt grade specs. I wonder if the metric bolt specs have brittle fracture ratings. Aerospace fasteners better though or I'm sticking to the bus. :-)

Jay

It is nice that someone has actually done a test. Just don't be like NASA and now believe that all grade 8 bolts can be bent.

Dan

=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0Dan

When I bent it further it snapped at the top end of the threads, with only a little deformation there. The shank is now bent into a U with

0.18" between the legs and the outside of the bend still hasn't cracked.

So for this particular Home Depot 'JH' bolt the rolled threads are brittle but the shank isn't at all. I feel better about using Grade 8 bolts for machinery axles, not so good about hammering on such a powerful & freedom-loving spring.

Jim Wilkins

If you get the chance, I'd be interested to know what the structural engineer says. Of course I guess it's possible that building codes around the world may vary, but I get the impression that friction type connections are the most common here in England.

Best wishes,

Chris

I'm going to see if I can buy a copy of that Astronautic Structures Manual. Hopefully I can persuade an American seller to ship it to England. Thankfully there's no import tax on books!

Best wishes,

Chris

Thanks for the nice comment Winston, much appreaciated :)

H.

:) --Winston

My daughter spoke with her engineer and he confirmed the impression I got from my web browsing; that bearing type joints have become prevalent in the US, at least in building construction.