"Bob La Londe" wrote in message
...
"Ed Huntress" wrote in message
...
"Bob La Londe" wrote in message
...
"David Billington" wrote in message
...
Bob La Londe wrote:
On 4/11/2011 8:29 PM, Ed Huntress wrote:
"Bob La wrote in message
...
On 4/11/2011 8:17 PM, Bob AZ wrote:
On Apr 11, 8:15 pm, Bob La wrote:
I have need of stainless for various applications and to be frank
the
local stores just don't stock much. The box stores have a modest
selection, but its all no grade listed Hillman crap. Their
stainless is
worse than their packaged screws if that's possible.
I would like to have some idea what to search for for grades
equivalent
to steel grades. Like what stainless bolt would I look for to be
roughly equal to a grade 8 steel bolt? A grade 5? Never mind
grade 2.
Like I said, "the box stores have Hillman crap."
Bob
McMaster-Carr. mcmaster.com
Bob AZ
A search for "grade 8 stainless" on their site only shows hex nuts.
In
the suggested search items it shows 18-8, but does not say if that
is the
same strength as Grade 8 bolts.
It's not. Not even close.
I think that a Grade 8 in stainless is one very special bolt --
either a
44X-series or a precipitation-hardening grade.
I did find some reference in a UK welding group that seemed to
indicate that A4-80 was close, but the only bolts I've found in that
so far are metric.
IIRC A4 is 316 and those fasteners won't be anywhere near a grade 8.
I've seen someone recently confuse metric 8.8 designation with grade 8,
a big difference. An 8.8 fastener is about the same as a grade 5.
This person claims some, but not all 316 bolts are close, but slightly
less tensile strength than grade 5.
http://reviews.ebay.com/Stainless-Bo...00000001623345
It depends entirely on the degree of work-hardening applied to the bolt,
and there is no standard for designating it. Annealed, 316 has about 30
ksi yield and 75 ksi ultimate tensile strength. (weak for steel)
Cold-drawn wire runs up to 95 ksi ultimate tensile. When you make a bolt
from it, it's generally cold-headed and roll-threaded. The strength
varies all over the bolt because of the uneven cold-working.
You can't heat-treat 316, except to anneal it.
Hi-strength stainless bolts are made from heat-treatable grades, either
400-series (such as 420 or 440), or precipitation-hardening grades (17-4
PH). You can harden 17-4 PH close to 200 ksi tensile. They cost a bundle
compared to ordinary bolts.
Thanks. Sometimes a "Grade 8" is the bolt for the job, and sometimes a
"Grade 5" is better. I was hoping to find an equivalent for both, but
that seems to be not practical. Grade 2 is rarely the best choice except
as a shear bolt on farm equipment. Looks like I have the choice of going
with quality (ARP) or unknown when it comes to stainless but no other way
to grade.
Stainless presents one issue that may or may not be important in a given
application. The issue is elongation; when weaker bolts are better in an
application, it's usually because their greater elongation -- their ability
to stretch, plastically, or to bend -- is important because of the nature of
the load.
Austenitic stainless -- the 300 series -- is not very strong in terms of
ultimate tensile strength, but a combination of good basic elongation,
combined with pretty extreme work-hardening ability, produces a very big
spread between yield strength and ultimate tensile strength. This can be
very useful in those applications where a bolt may be overloaded and should
yield, rather than break. A slightly bigger bolt of a weaker material may
substantially outperform a smaller but higher-strength bolt.
The hardenable grades of martensitic (400 Series) and
precipitation-hardening stainless *can* have very good elongation, but you
have to check the specs on specific grades if it's an important issue for
you. The elongation of regular alloy steel bolts is well-known and widely
published, if you want to compare them.
Otherwise, it's mostly a matter of how much money you want to spend for the
sake of corrosion resistance.
--
Ed Huntress