Paging the metallurgists

I'm looking to buy stainless steel disc bolts and caliper mounting bolts
for the Gixer. What grade of stainless steel should I be looking for as
they'll obviously require a very high shear strength, which I'm told A2
grade doesn't have?

TIA

 

A4 - it's more than paper.

 

irellevant, the shear force on even a bog standard steel bolt of the
appropriate diameter will be so great, particularly considering there
will be several of them radially around the disk, that it will be one
of the last things you need to concern yourself with, long before you
get there your pads and calipers will have disintegrated and your disk
itself warped.

I'd be more concerned about the galvanic effects of a stainless bolt in
a steel disk rotor going through to an alloy wheel hub.

stainless steel is a (IMHO) vastly over rated material, I see it
constantly used (particularly in the marine trade) because it was
selected for its visual properties, little heed being paid to its
mechanical properties.

http://www.hse.gov.uk/lau/lacs/47-17.htm

You need to do some research on "Thermomechanical Fatigue Behavior of
Stainless Steel Grades" IMHO before you go buying stainless fasteners
for modern motorcycle brakes....

 

Guy Fawkes says...

I'm sorry, but I'm hardly likely to take any advice from someone who
regards disc brakes as a bad thing on a motorcycle.

Thanks and all that, but **** off eh.

 

I never said that.

OK, I'll take 30 years of engineering experience with me, and leave you
to play with perhaps the most safety critical part of any motorcycle by
choosing components according to how shiny they are.

darwinism at work.

 

Guy Fawkes says...

Yes you did, in a thread where you were extoling the virtues of drum
brakes on the bike you'd chosen for your daughter. You claimed disc
brakes weren't needed on a motorcycle because they were dangerous.

Hardly. I asked for advice, I'll take it from someone who has a clue,
not yourself.

 

I'll just wait for things to unfold.

 

Sheet, I wouldn't wait too long.

 

The Austenitic grades are inherently weaker than the hardenable (i.e
martensitic) stainless steel grades. At which point I'll have to claim
some ignorance of what would be acceptable in that application because
all my experience is in 'warmer' aerospace applications. I do know from
(failure) experience that how the bolt is made, as much as what it is
made from, is important.

If it was my life on the line and I *really* wanted stainless steel, I'd
go for an 'AS' (SBAC) bolt in A286 or one of the 12%Cr steels (410
stainless or better.). I certainly wouldn't immediately go for a 304
stainless. The A286 would have a similar expansion coefficient to
aluminium (unlikely to be of much benefit with the low temperatures the
calipers and disc carrier are going to see).

There is still the potential for galvanic corrosion between the
stainless bolt and the disc carrier/caliper, but as they are often
anodised aluminium it's not that likely to be a problem. Especially as
you're:

a) unlikely to ride it much in winter (loadsa salt around)
b) going to clean the bike after each ride....aren't you?

btw, you really want to talk to an Engineer with materials experience
rather than a 'metallurgist' because the latter are just scientists. I
was going to offer to look up the correct AS bolt, because I have access
at work, but I'm just a metallurgist with pretensions to being an
Engineer. Better you talk to a specialist.

I'd go for titanium alloy bolts myself and avoid salty conditions. Have
you tried looking on http://www.tastynuts.com ?

 

Only if we pad it out.

 

no, I did not say that, but then I never expected you to base an
argument / flame on what people actually say or mean sans deliberate
misinterpretation.

I have more of a clue about such things than you would credit, which is
I guess par for the course with usenet and talking to people you have
never met.


I just deleted a follow up that was typed in here, it explained, with
links, how to precisely and easily work out the forces at work and then
look up in a table which materials were suitable. It would have taken
you all of three minutes and given you irrefutable factual data.

but you don't need that, you're too clever, you got a smart mouth and a
motorbike and a net connection, and you like shiny little baubles and
you don't like me, fine, life's too short.

when I come on here asking elementary engineering questions feel free
to tell me I don't have a clue eh.

for the rest of you, brake components such as disk mounting bolts are
like elevator cables, they have something known as a "safety factor",
do not buy either from anyone who cannot tell you what it (the SF) is
for that component, or if in doubt just buy the factory OEM part.

 

Chris H says...

Excellent. I'll take your advice and search out someone with the
relevant experience. Many thanks.

 

Lozzo wrote:

oops, you just missed him.

 

Thanks, squire.

 

This is UKRM.

This is UKRM.

This is...oh, I give up!

If he'd wanted a proper techy answer he would have posted the question
in sci.engr.metallurgy.

 

That would put the brake on it and it'll end up stationary.

 

I'm glad I don't have to read this thread via a GSM connection.


--
Dnc

B1200 - +30bhp ~|~ ZZR1100 - faster when upright
V2300 - flat cap and rug ~|~ VS800 - borked

MIB#26 two#54(soiled) UKRMMA#26 BOTAFOT#153 X-FOT#003

 

my first reply wasn't "techy", it was straightforwards and accurate,
and if he'd followed the links given he'd have found high chrome 400
series stainless and not shitty 316 and understood the difference
between the two.

his problem wasn't with the content of the response he got from me, his
problem was the response from me.

like I said, life's too short.

 

It's called 'common sense'.

 

Guy Fawkes says...

I have a smart brain and a net connection. I don't know much about
engineering so I ask of those who do know. I don't take advice from just
anyone, especially anyone who's shown themselves to be a clueless
fuctard in the past. Your stupidity reared its ugly head regarding disc
brakes, the very subject I have a query on. I am hardly likely to take
your advice on this subject, regardless of how qualified you say you
are.