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Old 04-07-2020, 10:04   #16
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Re: Silicone bronze vs stainless steel for teak deck fastening

304 SS has been unfairly maligned. It is stainless steel so doesn't corrode like plain steel but is not as stain resistant as 316. It is stronger so better used when the engineers start pushing the limits of weight/strength. Think the biggest problem is poor quality metal in the fasteners that are coming from offshore that you get in HD, etc. Talking about offshore, most of the quality SS comes from S. Korea which has pretty much cornered the market on stainless wire.

Have not had good luck with square drive fasteners. Really appreciate the ability to put the fastener on the square bit and have it stay there when doing boat yoga but they strip out way too easily. Discovered screw extractors when I tried using square drives. The camm'd out square drive puka does make it easy to use a screw extractor, however. Unfortunately have had to waste too much time using the extractors with square drive fasteners.
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Old 04-07-2020, 10:21   #17
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Re: Silicone bronze vs stainless steel for teak deck fastening

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Originally Posted by Cheechako View Post
Any 18-8 is fine. Of course 316 is great but I don't know how available and hoe much mor money they are.
I like "sheet metal screws", the ones threaded all the way up, as opposed to actual tapered wood screws. Far better. Most don't use the wood screws anyway though.
While I have not replaced the screws on a teak deck, I have done a lot of woodworking over my 80+ years of life. Wood screws have a smooth portion of the shank and a threaded portion. The smooth portion allows the wood to be drawn tightly into the wood that you are drawing it into. If the whole screw is threaded like a sheet metal screw the deck can be forced away from the underlayment. I do not recommend sheet metal screws for this application. (Also be sure to use flat head screws, saw once where some knucklehead used round head sheet metal screws to try to refasten the deck on a pristine GB42. Bungs popped in a few weeks) Good luck and tell us how this comes out.
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Old 04-07-2020, 10:48   #18
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Re: Silicone bronze vs stainless steel for teak deck fastening

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Is crevice corrosion not an issue with stainless screws in this application? I would have guessed that it could stay damp around the screw with no ability to flush out the oxygen depleted moisture and quickly rust away.

I have also snapped plenty of SS screws going into glass and dense wood over the years. Is bronze that much worse? All the interior on my boat is fastened with bronze and the main problems I've had were the screws corroding away where they got wet and the phillips head stripping out. A few have snapped but not that many.
From my experience, yes Bronze is worse. And I'm talking brand new bronze too. Go figure. I totally agree that you would think crevice corrosion should be bad in there. But... that's my experience.
I have removed the teak decks on two boats (what a job!) Surprisingly, snapping off SS screws was rare. More often the phillips head would strip out. But screws in fiberglass will definitely break off.
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Old 04-07-2020, 10:57   #19
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Re: Silicone bronze vs stainless steel for teak deck fastening

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While I have not replaced the screws on a teak deck, I have done a lot of woodworking over my 80+ years of life. Wood screws have a smooth portion of the shank and a threaded portion. The smooth portion allows the wood to be drawn tightly into the wood that you are drawing it into. If the whole screw is threaded like a sheet metal screw the deck can be forced away from the underlayment. I do not recommend sheet metal screws for this application. (Also be sure to use flat head screws, saw once where some knucklehead used round head sheet metal screws to try to refasten the deck on a pristine GB42. Bungs popped in a few weeks) Good luck and tell us how this comes out.
Not my experience at all. In fact, in the real world where you are going into fiberglass often, a wood screw may bottom out leaving no thread left and thus not pulling the wood down to the fiberglass.
For example: When using bungs in a say 3/4" plank, by the time you properly countersink 3/8" plus for a bung, you have less than 3/8" wood left under the tapered screw head (more like 1/4-5/16" left below the taper) Your wood screw is not going to pull tight as it doesn't have enough thread.

I do understand your theory though.... if the hole in the wood you are passing through is too small, then the thread on a sheet metal screw could grip there instead of the fiberglass you are going into. Although in reality the screw just carves out some wood usually.
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Old 04-07-2020, 14:08   #20
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Re: Silicone bronze vs stainless steel for teak deck fastening

With bronze screws it is easy to strip them out on top by using the wrong type of driver bit. Often these are not Phillips headed but Frearson flat head screws which take a different bit. The slots of the Fearson are more square sided and not beveled so much as a Phillips. The Fearson bit fits very snugly and with less "slop" in the top of the screw which helps keep the driver from slipping out of the slots and stripping the softer bronze.
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Old 04-07-2020, 16:39   #21
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Re: Silicone bronze vs stainless steel for teak deck fastening

I would like to know if this deck is screwed into a molded fiberglass deck, or a wooden one: they are very different problems calling for different solutions.

My teak deck is over plywood and beams, and I used silicon bronze wood screws when I built her - in 1978. The only shortcoming is that the bronze is soft enough that it is easy to round the internal head (Frearson, or Reed+Prince) when removing them for refastening - so it is very important to remove any glue or debris from the head such that the driver is fully seated. Of course the bronze can develop an oxidized layer if salt water gets to it, but it doesn't travel (i.e. no visible staining on deck). AFAIK stainless wood screws are not readily available (everyone seems to be using sheet metal screws which are not appropriate for wood). And depriving SS of oxygen (under a bung) while wetting it with salt water can cause stains - depending on the quality of stainless. Of course using a quality tapered pilot drill with countersink and counterbore is necessary. Refastening with the old screws, and deepening the holes with the same pilot/counterbore, works well.

Putting teak down on a molded fiberglass deck with SS screws is a really bad idea. They leak. A SS screw is the irresistible force to the fiberglass immovable object: something has to give. Typically a SS screw creates pressure as the wider taper is driven into the FG, causing a crushing of the resin. The hole can no longer be sealed with the normal caulking as the loose glass strands prevent penetration. I have helped repair such holes, and they can be a nightmare to even locate as the water often gets under the teak elsewhere and then travels to the damage unseen. Epoxy is probably the only hope for sealing such holes; personally I have drilled a larger, clean hole then filled with caulking and plugged, but I claim no special expertise here. It seems that it is possible to use a pilot that is only slightly smaller than the screw and not always fracture the structure, but in the long run some holes are likely to fail. Driving bronze screws into fiberglass usually deforms the screws, and they can seize in the hole and even break off - not a really good idea. Again, there might be an ideal hole size that only slightly deforms a bronze screw but I wouldn't recommend it. There is a reason that modern boats put teak decks down with epoxy and a vacuum bag - and no screws at all.

If by chance you have a cored fiberglass deck under the teak then choosing a tapered pilot drill that doesn't allow the screw to pressure the FG but uses the core for grip should work. Then a durable solution can be had with screws, assuming the core is not foam or rotten.

While the screw holes in the fiberglass provide the conduit for leaks, leaks often start by water travelling under the teak to the screws (the sealant often fails between the teak and FG). If it is just a leaking or missing bung then that is no big deal. But if, as often happens, the water is under the teak already then a proper repair would include re-laying the planks with adhesive sealant. At that point removing the teak, filling the holes, then painting the deck is the preferred solution. Or instead of paint, put down teak (or faux teak) with an adhesive and no screws.

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Old 04-07-2020, 18:34   #22
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Thumbs up Re: Silicone bronze vs stainless steel for teak deck fastening

If you can use silicon bronze,if the deck is teak over glass or is it cored with some material ,if cored with wood eg ply or balsa or timber planks there is a better way no harder or time consuming,.if the seams are shot not to worry ,the best way to refasten the teak regardless of thickness is as follows ,if the plugs are ten or twelve mill ,3/8 or 1/2 inch,use the suitable drill with depth gauge fitted or small hole saw ,if the old fastening has been removed use the drill to go through the teak ,the glass into the core about the depth of the diameter .with a long plug cutter cut new plugs slightly longer than the depth ,fit with good epoxy,this is virtually trunneling, and if done properly results in a solid teak deck ,if the planks are loose temporarily hold the planks down with large washers and self tapers in the seams ,if the old fastening are still in place use the hole saw through a drill plate over the old fastening .The seams can be routered or outher wise restored ,this method is tried and true ,watertight and long lasting.
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