US source for 316 stainless screws, etc? Especially metric

[Cheechako]

Originally Posted by dlj

I keep hoping to find a source for 17-4 PH fasteners. McMaster has some but a limited range of sizes. Going through all the above links, I'm not finding any that carry that type of stainless fastener... Too bad, that's an amazing material for marine fasteners....

Oh well, I'll keep looking.

dj

17-4PH is an amazingly strong material. Like 2-3 times stronger than 316. I've worked with it in aerospace quite a bit. It requires a lot of close control to make it anti corrosive though, unlike the austenitic SS's such as 304-316.
It has a high iron content IIRC. The "PH" means "precipitation hardened" or heat treated for strength. Appropriate polishing or surface conditioning is necessary for corrosion resistance also. All of that makes for difficulty in producing bolts commonly I imagine.

High quality Wichard shackles etc are made from 17-4PH and have served me quite well on boats.

[markxengineerin]

https://marine.wichard.com/en/stainl...les/part-11245 Here's a 17-4 shackle that includes what is basically a bolt. I wonder if that part of it is 17-4? It would be interesting to see apples to apples crevice corrosion (or any corrosion) test results from this shackle vs. the same in 316. I am more interested in the corrosion resistance than the strength, as it's usually easy to make something bigger, but not easy to spot crevice corrosion before it can become a danger.

[Cheechako]

Originally Posted by markxengineerin

https://marine.wichard.com/en/stainl...les/part-11245 Here's a 17-4 shackle that includes what is basically a bolt. I wonder if that part of it is 17-4? It would be interesting to see apples to apples crevice corrosion (or any corrosion) test results from this shackle vs. the same in 316. I am more interested in the corrosion resistance than the strength, as it's usually easy to make something bigger, but not easy to spot crevice corrosion before it can become a danger.

I imagine it's all 17-4. I used similar Wichard Shackles on anchor systems for the strength with high test chain. Although I opted for more D shaped shackles with the straight sides rather than the Bow Shackle. I saw no apparent corrosion after 2.5 years use in the Caribe. Possibly a no-no in some opinions to have the galvanized chain with the 17-4ph, but it seemed to be fine.

More this type: https://marine.wichard.com/en/stainl...kles/part-1405

But a genuine Crosby shackle is probably as strong rating wise.

[SuW]

Originally Posted by 5BTM

Thank you!!

Priceless info for someone living in the Montreal area, the retail desert of Canada.

For boating stuff we also like the Chandlery (Ottawa), Marine Outfitters (Kingston) and The Binnacle (Halifax). They all ship at reasonable cost, imo.

Defender also ships to Canada, but at least the Chandlery will try to price match, perhaps the others too. It's quite competitive.

I don't know why Montreal should be so poorly served, there are a lot of boaters there!

[dlj]

Originally Posted by markxengineerin

I think I remember discussing this with you in an older thread (chainplate materials), but could you say more about why? https://www.aalco.co.uk/datasheets/S...2-Bar_100.ashx
"Corrosion resistance is similar to that found in grade 304 stainless steel."
I looked into 17-4 but was quickly turned off by the google research, but you must have your reasons..

When I was training engineers in materials, I would tell them Google is not your friend. You are demonstrating just one of the many reason for that in your statement above.

When you did your "research", did you note what heat treat condition the above information related to? Or did Google even have that information for you to look at, not unlikely they did not. The data sheet you put the link into, does not define what heat treat condition was used to give you their "corrosion resistance" data...

That information is based upon a common heat treat condition of H900 for 17-4 PH. In fact, most internet data for this alloy will only address the properties of 17-4 PH in the H900 condition. Even the really expensive databases that companies spend tens of thousands of dollars on, have very limited data on the precipitation hardening alloys. I digress....

There are numerous other heat treat conditions for 17-4 PH that have both different mechanical properties and corrosion resistance properties. In the fastener industry, for nuts, bolts, screws, for example, they often use H1100 heat treatment for their fasteners.

In the marine environment - let me give you an example - 316 an alloy everyone uses and is quite familiar with - is not rated for underwater application. 17-4 PH in any heat treated condition above about H1000 (I would likely not use under H1050) is rated for underwater usage. Not quite the same corrosion resistance of 304, would you agree?

dj

[dlj]

Originally Posted by Cheechako

17-4PH is an amazingly strong material. Like 2-3 times stronger than 316. I've worked with it in aerospace quite a bit. It requires a lot of close control to make it anti corrosive though, unlike the austenitic SS's such as 304-316.
It has a high iron content IIRC. The "PH" means "precipitation hardened" or heat treated for strength. Appropriate polishing or surface conditioning is necessary for corrosion resistance also. All of that makes for difficulty in producing bolts commonly I imagine.

High quality Wichard shackles etc are made from 17-4PH and have served me quite well on boats.

In aerospace you have likely used H900 heat treatment for this alloy. In which case what you say is correct. However, in the heat treatments above H1000 that is not the case.

Bolts are typically heat treated to these higher heat treatments to lower notch sensitivity and to eliminate or reduce corrosion problems.


dj

[s/v Jedi]

The Wichard HR shackles are very strong but they will require polishing as they start looking rusty after a while.

I’m happily swapping them for Dyneema

[dlj]

Originally Posted by s/v Jedi

The Wichard HR shackles are very strong but they will require polishing as they start looking rusty after a while.

I’m happily swapping them for Dyneema

Love my soft shackles. But not on anchor rode...

dj

[s/v Jedi]

Originally Posted by dlj

Love my soft shackles. But not on anchor rode...

dj

For anchor rode I only use the real deal and that is Crosby or one of their equals.
https://defender.com/en_us/crosby-g-...anchor-shackle

[two-rocks]

I can't believe I'm the first to post this.

boltdepot.com

I have bought lots of fasteners from them, great company and service. Bought the wrong length for attaching my t-track - returned them years later (original quantity, no return date limitations!).

[hlev00]

Originally Posted by two-rocks

I can't believe I'm the first to post this.

boltdepot.com

I have bought lots of fasteners from them, great company and service. Bought the wrong length for attaching my t-track - returned them years later (original quantity, no return date limitations!).

You aren't the first, but I appreciate the extra recommendation. I have found exactly what I needed there.

[Shrew]

Originally Posted by s/v Jedi

how do you tell if the 316 fasteners at Home Depot, Lowe’s, FastenAll, Bolt Depot, Ace etc. are actually 316 and not 304?

All the ss I've used from the large box stores mentioned rusts very, very quickly. They behave like 304ss would in a saltwater environment. Ace Hardware labels their fasteners as 304 and 316 specifically.

I have no way to tell 304 from 316ss by looking at it, but the stuff I get from West Marine and Ace behaves like what I'd expect in 316.

Ordering, for me, is problematic as I'm not a good planner and tend to have to take parts in with me to test sizes until I figure out what I need.

[two-rocks]

Originally Posted by hlev00

You aren't the first, but I appreciate the extra recommendation. I have found exactly what I needed there.

Ha! It was in the second post. Speed reading has also caused me to order lots of extra bolts.

[s/v Jedi]

Originally Posted by Shrew

All the ss I've used from the large box stores mentioned rusts very, very quickly. They behave like 304ss would in a saltwater environment. Ace Hardware labels their fasteners as 304 and 316 specifically.

I have no way to tell 304 from 316ss by looking at it, but the stuff I get from West Marine and Ace behaves like what I'd expect in 316.

Ordering, for me, is problematic as I'm not a good planner and tend to have to take parts in with me to test sizes until I figure out what I need.

Exactly, the fasteners from Amazon hold up much better than from Lowe’s and Home Depot. I do like Ace and have more trust there…

[markxengineerin]

The data sheet you put the link into, does not define what heat treat condition was used to give you their "corrosion resistance" data...

That's right, it's hard to find information on what I'm curious about, which is a measure of resistance to crevice corrosion in a marine environment (under salt water or exposed to the spray), 316 vs. 17-4 in a condition that's most suitable for something like a shackle, chain plate, or bolt. I don't know if such a metric as "resistance to crevice corrosion" exists, but it would be nice if it did, given the number of failures it causes on just about every boat. If you know more, please share.