Stainless fasteners
- Thread starter JoeBTB
- Start date
Some may be as good, some may be better and some may be worse. There are many different types/mixes of stainless steel. Each is designed for a specification. I have been told, and have had some success verifying, that the "better" stainless steels have less magnetic attraction than regular steel. In this case better is defined as being a more pure stainless.
G
G
Well, I'm never impressed by WM. But I wasn't sure if there's such a thing as "marine grade" stainless. I'm about to rebed some stanchions, and I'm planning to replace the bolts and nuts. For reasons I can never fathom, WM never keeps their shelves stocked, so of course they only have a couple of what I need. The local hardware store has plenty, they look just as good, and they're less expensive than WM. Generally, I'm amazed WM can even stay in business.
There are two major series of stainless steel ; 300 and 400 series. The 300 that are easily available are SS304 and SS316. SS304 may contain traces of carbon, thus it is magnetic, due to the manufacturing process. SS316 is chemically resistant and I would use this type for marine application although it is not as strong (strength) and as heat resistant as SS304.
I saw a guy restocking SS fasteners at WM one afternoon while I was picking out some SS screws. A few days later I went to the the Ace Hardware close to where I live to buy some more SS fasteners that I needed to finish the job. The same guy was restocking the SS fasteners there. I said hello this time and we did a little hardware talk. Yes, both stores were stocked by the same fastener company. The SS fasteners were the same in both stores, only the price was different. I suspect WM looses money with the fastener aisle (even at their higher markup), but they offer it as a convenience to boaters who need these items to complete more expensive projects they purchase at the store. Incidentally, I sometimes walk in to the fastener company and buy there directly if I can't find an item (like silicon bronze fasteners) anywhere else. The fastener company retail price is higher than the Ace Hardware price.
If you need lots of fasteners and want to buy by the box, there are big discounts available from some online and mail order fastener specialists.
If you need lots of fasteners and want to buy by the box, there are big discounts available from some online and mail order fastener specialists.
Better or wqrse depends on the supplier. If you can not find what you are looking for locally, try Mcmaster Carr. That have any and every thing you could look for in the way of fasteners, fitting etc.
Two examples, I needed nylon 1 1/2" nylon 90's for my holding tank plumbing. I needed 8 of them. WM had 2 **9.99ea. Mcmaster Carr as many as I wanted at about $5 each. I also need a 1 1/2" to 3/4" reducer for a thruhull. I could not find one locally anywhere. Mcmaster Carr, has them and shipping is quick.
As far as stainless nut bolts and screws try Lowes, they have a good selection.
Two examples, I needed nylon 1 1/2" nylon 90's for my holding tank plumbing. I needed 8 of them. WM had 2 **9.99ea. Mcmaster Carr as many as I wanted at about $5 each. I also need a 1 1/2" to 3/4" reducer for a thruhull. I could not find one locally anywhere. Mcmaster Carr, has them and shipping is quick.
As far as stainless nut bolts and screws try Lowes, they have a good selection.
"There are two major series of stainless steel ; 300 and 400 series. The 300 that are easily available are SS304 and SS316. SS304 may contain traces of carbon, thus it is magnetic, due to the manufacturing process. SS316 is chemically resistant and I would use this type for marine application although it is not as strong (strength) and as heat resistant as SS304."
Having spent about 40 years in the 'metal' business machining, welding (including nuclear certified),
metalurgy and mechanical engineering please let me set this straight.
The 300 type stainless steels are known as 'austenitic' steels. They are not magnetic in any form and are chromium/nickle alloys having less than 0.1% carbon. These alloys are not heat treatable.
The 400 type stainless steels are known as 'martinsitic' steels. They are magnetic in all forms and are
straight chrome alloys with less than 0.15% carbon. These alloys are heat treatable.
The 400 types exhibit lower resistance to corrosion that the 300 types in most uses including salt water
applications.
316 stainless has much better resistance to corrosion and better mechanical properties than 304 stainless
due to the inclusion of molybdenum. It is non-magnetic in the annealed condition but when work hardened
to the extreme can exhibit very slight magnetic properties.
304 and 316 are the most common alloys used in boat parts and fasteners. Both alloys are available in
low carbon versions which preclude carbide precipitation in the 800*-1500* F range, such as might occur
in welding. The low carbon alloys are designated as 304L and 316L and both exhibit less surface rusting when passivated, especially after forming operations.
316L is especially desirable for use in chloride environments such as salt water as it has much greater
resistance to crevice and intergranular
corrosion.
316 or 316L is the best alloy for boat fasteners. However, most of the fasteners found in hardware stores
and the usual boat store are 304 alloy. This is perfectly fine for above waterline applications. For below
waterline applications 316L should be used especially where long term strength and corrosion resistance
is critical. 304 may be used below the water line but may require more frequent inspections/replacement.
Hope this helps,
Pete
Having spent about 40 years in the 'metal' business machining, welding (including nuclear certified),
metalurgy and mechanical engineering please let me set this straight.
The 300 type stainless steels are known as 'austenitic' steels. They are not magnetic in any form and are chromium/nickle alloys having less than 0.1% carbon. These alloys are not heat treatable.
The 400 type stainless steels are known as 'martinsitic' steels. They are magnetic in all forms and are
straight chrome alloys with less than 0.15% carbon. These alloys are heat treatable.
The 400 types exhibit lower resistance to corrosion that the 300 types in most uses including salt water
applications.
316 stainless has much better resistance to corrosion and better mechanical properties than 304 stainless
due to the inclusion of molybdenum. It is non-magnetic in the annealed condition but when work hardened
to the extreme can exhibit very slight magnetic properties.
304 and 316 are the most common alloys used in boat parts and fasteners. Both alloys are available in
low carbon versions which preclude carbide precipitation in the 800*-1500* F range, such as might occur
in welding. The low carbon alloys are designated as 304L and 316L and both exhibit less surface rusting when passivated, especially after forming operations.
316L is especially desirable for use in chloride environments such as salt water as it has much greater
resistance to crevice and intergranular
corrosion.
316 or 316L is the best alloy for boat fasteners. However, most of the fasteners found in hardware stores
and the usual boat store are 304 alloy. This is perfectly fine for above waterline applications. For below
waterline applications 316L should be used especially where long term strength and corrosion resistance
is critical. 304 may be used below the water line but may require more frequent inspections/replacement.
Hope this helps,
Pete
- Joined
- Oct 20, 2002
- RO Number
- 10503
- Messages
- 3,677
OK so far, but how do we know what number 300 or 400 we are buying?
Also, I've always used Bronze below the water line, stainless above.
Also, I've always used Bronze below the water line, stainless above.
- Joined
- Jan 1, 2000
- RO Number
- 3238
- Messages
- 4,831
Thud, I've heard the same thing, but with the caveat that one should avoid using dissimilar metals... So if you have SS, stay with that; if you have bronze, stick with it. IMHO
edit: ( at least, in the same area. so if bronze below stay with it there, but you cn still use SS above )
edit: ( at least, in the same area. so if bronze below stay with it there, but you cn still use SS above )
I stick with the original fastener types with our 50's era wooden Chris-Craft. CC used silicon bronze wood screw for all wood to wood fastening then (above and below waterline).
I do make one general exception though, and use 304 stainless to replace worn-out chromed or nickle-plated brass fasteners that were used for fastening deck hardware to wood.
The SS fasteners I get at the local marine store or less expensively at Ace Hardware is called 18-8 stainless, which is essentially 304 stainless. As I understand it, 18-8 stainless is a general designation that includes closely similar 304 types: 302, 302HQ, 303, 304, 305, 384, and XM7 stainless steel.
I use SS oval head philips sheet metal screws for fastening deck hardware to wood where the full holding strength of a wood screw is not required. Most of these screws are used on varnished wood, so they have to be removed and refastened at least once a year for varnish recoats. I treat the screw holes with Captain Tolley's Creeping Crack Cure (!) every time. This is a penetrating polyurethane sealant that maintains the screw threads in the wood and insulates the wood from galvanic corrosion. The screws are also bedded each time with Sikaflex, Boatlife or similar sealant.
I do make one general exception though, and use 304 stainless to replace worn-out chromed or nickle-plated brass fasteners that were used for fastening deck hardware to wood.
The SS fasteners I get at the local marine store or less expensively at Ace Hardware is called 18-8 stainless, which is essentially 304 stainless. As I understand it, 18-8 stainless is a general designation that includes closely similar 304 types: 302, 302HQ, 303, 304, 305, 384, and XM7 stainless steel.
I use SS oval head philips sheet metal screws for fastening deck hardware to wood where the full holding strength of a wood screw is not required. Most of these screws are used on varnished wood, so they have to be removed and refastened at least once a year for varnish recoats. I treat the screw holes with Captain Tolley's Creeping Crack Cure (!) every time. This is a penetrating polyurethane sealant that maintains the screw threads in the wood and insulates the wood from galvanic corrosion. The screws are also bedded each time with Sikaflex, Boatlife or similar sealant.
Well, there's the $64 question. The only way I know to be certain is:
1) Catch the fastener guy at the hardware store (not the clerk) and make him show you what alloy and make him show you that all 'batches' are the same. Hmmmm. I've had the guy around here bring me box quantities from time to time. Your guy may not.
2) Repeat the above at the 'marine' store. Hmmmm. No luck there, they can't handle 'specials'.
3) Buy the fasteners from an outfit that specifically deals in fasteners, request 316L, and make them supply the certification. $$$$$$.
4) For anything 'non critical' just don't worry about it!!
Pete
You can find a good info page on the characteristics of 18-8, 304, and 316 stainless online at Bosun Supplies, Co. They are marine SS specialists. There are some strength advantages for 18-8 and 304, while 316 has some anti-corrosion advantages.
- Joined
- Feb 23, 2004
- RO Number
- 12830
- Messages
- 674
The nicest stainless I've laid hands on was out of England and France. I think it was manufactured by Wichard.
- Joined
- Oct 20, 2002
- RO Number
- 10503
- Messages
- 3,677
Well....I was once cooped up in a Hotel bar with a Stainless salesman from Sheffield England. Does that count?
Boeing was in his Territory.
He was so interesting. Explaining all the customers he had and what they did with the stainless.
He told me stainless can be mixed with almost anything to make what some folks call "exotic" metals.
OK so I'm a little bit knowlegable....we better stick to Pete's certified knowlege for this thread.
Boeing was in his Territory.
He was so interesting. Explaining all the customers he had and what they did with the stainless.
He told me stainless can be mixed with almost anything to make what some folks call "exotic" metals.
OK so I'm a little bit knowlegable....we better stick to Pete's certified knowlege for this thread.
Pete, thanks,
You saved me a lot of typing. 40 years in a met lab and certified welding inspector, I was about to set a few facts straight, but you saved me the time. Again folks, what Pete said is gospel and take it as such.
You saved me a lot of typing. 40 years in a met lab and certified welding inspector, I was about to set a few facts straight, but you saved me the time. Again folks, what Pete said is gospel and take it as such.
quote:
--------------------------------------------------------------------------------
Originally posted by Thudpucker
OK so far, but how do we know what number 300 or 400 we are buying?
--------------------------------------------------------------------------------
I have stainless steel bolts in my shop and the heads are stamped S304 and another bolt is stamped S316 with designation THE. I also used a magnet to check and found that S304 is magnetized and S316 is not.
Pete's got a good point. Use SS316 for below water line and use S304 for above the water line.
--------------------------------------------------------------------------------
Originally posted by Thudpucker
OK so far, but how do we know what number 300 or 400 we are buying?
--------------------------------------------------------------------------------
I have stainless steel bolts in my shop and the heads are stamped S304 and another bolt is stamped S316 with designation THE. I also used a magnet to check and found that S304 is magnetized and S316 is not.
Pete's got a good point. Use SS316 for below water line and use S304 for above the water line.
Wow, fantastic information -- you guys amaze me. I went with "just not worry about it" for my task today. [^] Rebedding the stanchions went well, much much better than I expected. They came apart easily and went back together easily. I made a bit of a mess with the 3M 101, but otherwise all is well. Just need to go back next week and tighten them down the rest of the way.
Thanks for the stainless info!
Thanks for the stainless info!