View Full Version : silicon bronze screws

12-04-2003, 04:30 PM
Can there be more than one manufacturer of silicon bronze screws or different specifications? I am getting ready to order more but Jamestown Distr doesn't offer 1000 quality discounts as does McFeely and a local supplier but I question whether they are all the same screws as I originally got from Jamestown? Has anyone experience with McFeely's silicon bronze? Even they offer two types of silicon bronze: "boatbuilding" and "marine grade". I can't imagine there is more than one manufacturer for this limited demand product.

Ken Hutchins
12-04-2003, 04:53 PM
Try Standard, in New Bedford MA. Tell em you want qty discount. Me thinks you will be happy.
Standard (http://www.babbittsteam.com/standard.htm)

12-04-2003, 05:00 PM
Originally posted by Ken Hutchins:
Try Standard, in New Bedford MA. Tell em you want qty discount. Me thinks you will be happy.
Standard (http://www.babbittsteam.com/standard.htm)I'll second that. Are you after Robertson (square) drive screws? Standard has 'em. Me thinks you will be happy with the Robertson head screws.

12-04-2003, 09:14 PM
I'll third the Standard recommendation. Jamestown has been excellent for lots of things and especially when we just need a few odd size screws or bolts, but for bulk, Standard seems to be the way to go.

Happy screwing...well nevermind :rolleyes:

12-04-2003, 10:58 PM
I have a question? What the hell is the difference between boatbuilding and marine? Or is this just a slick sales job to sell lower quality silicon bronze at cheaper rates? I have seen a lot of complaints lately concerning silicon bronze, this board has a guy asking just a few months ago where to get the bronze screws tested, and as i remember his screws where deteariating in his boat after only 6 years. So do you have to rely on the distributor being honest in the quality?

12-05-2003, 09:18 AM
Mcfeely's boat-building vs marine designation isn't about material, but shape of the screw. Most notably the diameter of the shank. The boatbuilding screws have a full sized shank whereas the others have a reduced shank. The reduced shank makes life a little easier for most woodwork, and the full shank fits the pilot hole tighter eliminating the tiny void around the shank.

For a picture try going here: regular vs. boatbuilding (http://store.yahoo.com/squaredrive/fasteners-screws-flat-head-silicon-bronze.html)

ps: personally, I would think that careful selection of pilot/countersink bits would make either screw shape fit tightly enough.

[ 12-05-2003, 09:28 AM: Message edited by: scepticus ]

Bruce Hooke
12-05-2003, 10:12 AM
I would dispute the logic for the different screw types offered by Mcfeely's but not the need for the full-size shank type. IMOOP it's not about the need to fill the hole to keep water out (although that's not a bad idea), it's about the fact that in many cases the place most prone to corrosion is the section of the screw that is right at the boundary between the two pieces of wood. Ideally this point should be on the full size shank rather than in the threaded portion where there is less metal so corrosion can cause more trouble. Of course, the unfortunate truth of the matter is that the geometry often works out such that the threaded portion starts too soon. However, this brings up another advantage of screws with full size shanks inserted into holes drilled to match. With the reduced size shank, if some of the threads are still in the "top" piece (e.g., the plank rather than the frame) when the screw is fully seated the threads may well bite into the top piece and prevent it from being pulled tight against the underlying piece (e.g., the frame). For this reason I still drill a stepped pilot hole even if I am using reduced shank screws, and having drilled such a hole there is not much advantage, other than price and availability, to using reduced shank screws (althought I do all the time for non-boatbuilding stuff because there is also no big disadvantage either if corrosion is not an issue).

Bruce Hooke
12-05-2003, 10:13 AM
Suprising as it may seem there appear to be quite a few manufacturers of Silcon Bronze screws and by all reports the quality does vary...

12-05-2003, 03:37 PM
Thanks for the Standard referral; I will give them a call.

12-05-2003, 05:07 PM
I for one think this has been a quite informative thread. The link to regular verus boatbuilding screws sure helps to exsplain why a lot of people are complaining about screws breaking so easily. With the screws shank being thinned down around the threaded area, once the thicker shank area grabs, the resistance snaps the thinner shank right off.You would have to use a double sized pilot hole for these cheaper screws.But i have also read complaints about how easily silicone boat nails break. I have ordered from jamestown and glen-l and so far have not been dissapointed. Just used a whole bunch of silicon boat nails from glen-l, and before using them tested them. Drove several through a piece or wood, bent them over and then straightened them and drove them back. NO PROBLEM. But i have read where others complain that you bend the nail slightly and try and strighten it, and they break right off.Mine didn't, so why did there's? It would have to be the alloy mixture, which means there has to be different quality bronze fasteners being sold, and the home boatbuilder isn't aware of this.It is a shame to spend the money on bronze and think you are using the best there is for a marine enviorement, only to find they easily break or even worse in only a few years they are deteriorating. Have heard ( and believe it) that the bronze fasteners that are deteriorating and breaking so easily are poor alloys that are being shipped in from asia. If this is the case, you might be as well off just using drywall screws.Hate to sound so negative, but to spend the time and money to build a boat, and then find out the fasteners aren't up to snuff, is a little dissheartening. Go for quality and not price.

12-05-2003, 06:11 PM
Has anyone bought BRONZE boat screws from HAMILTON MARINE ? What is their quality like ?

I found their pricing to be way lower than that of Jamestown and McFeely as advertised on the web.

Am interested because I will shortly need to refasten the underwater hull.

Thanks also for tipping us off on the other supplier who gives quantity discounts

Bruce Hooke
12-05-2003, 06:22 PM
Originally posted by carioca1232001:
Has anyone bought BRONZE boat screws from HAMILTON MARINE ? What is their quality like ?

I found their pricing to be way lower than that of Jamestown and McFeely as advertised on the web.

Am interested because I will shortly need to refasten the underwater hull.

Thanks also for tipping us off on the other supplier who gives quantity discountsI have purchased bronze screws from Hamilton Marine and I have never had any problems with them, however, most of the screws in question are in a boat that is still under construction. Hamilton Marine is, I believe, the biggest supplier of bronze screws and similar stuff in Maine, which is one of the two major centers of wooden boat building in this country. So I would be very surprised if they were supplying an inferior product.

12-05-2003, 06:28 PM
I bought screws and other assorted fasteners from Hamilton Marine. Other than go in as they are supposed to, I can't comment on quality. They are only a few months old.

I also bought screws from Clark Craft Fasteners. Simply because they had the only #6x1-1/2" oval head bronze screws I could find. They are working fine also.

Most of the screws in the boat are bronze Robertson drive from Standard Fasteners or Hamilton Marine because those are the sources that John Anderson the builder trusts.

12-05-2003, 06:29 PM
Bruce Hooke,
Thanks for the reference on HAMILTON MARINE.
Itīs amazing how swiftly help is dished out on this Forum !

12-10-2003, 06:01 PM
You can also try C.E. Beckman Co. (http://www.cebeckman.com), can't order online, but you can phone in an order... or I think there is another company that is in wooden boats advertisements...

With regards to bronze screws... I believe there are 3 different plants in the Far East that most fastener companies are getting there screws from.

One of the plants, produces a crap product... the wood screws are not really tapered, more like a tapping screw...

but thats just my $.02

12-10-2003, 09:52 PM
There are different grades of silicon bronze, and dozens of different treatments for these grades that will affect their properties. I think that most or all of your fasteners would be either 651 (low silicon)or 655 (high silicon), but the range in final properties is all over the map, depending upon whether they are hardened, annealed, tempered, etc. The tensile properties seem to range anywhere from 40 ksi to 120 ksi, with elongations from 15% to 60% (elongation is a measure of ductility, and means that after you have pulled a bar of the material beyond its ultimate tensile strength and broken it, when you put the two halves back together, the total length will be 15% or 60% greater than it was when you started out). Generally, the higher the elongation, the softer the material, and the lower the elongation, the harder (but more brittle) the material. Like taffy vs. glass. For the type of small boats that I build, I am willing to sacrifice a little strength for a little more ductility, so that there is less chance of snapping heads off.

Your fastener distributors probably don't advertise what grade they are selling because they probably don't know. It may vary from shipment to shipment, depending on what deals were available at the time. Especially if they are purchasing from overseas suppliers. My experience in the metallurgical field has been that some younger companies in the industry aren't real concerned with hitting chemistry specifications of their alloy mixes very carefully. They are more interested in getting a foothold in a competitive industry, which they can do with lower prices because they may be cheating on their materials. So the long and the short of it is, unless you have some testing done on your batch of fasteners, you may not know for sure what you just bought.


12-11-2003, 10:21 AM
The McFeely's paper catalog has a box of stats about their silicon bronze screws. I don't have it with me and I don't recall just what information was in there, but it was stuff about tensile strength and such. I couldn't find that sort of info on their web site but one could probably call them and ask.

12-11-2003, 11:53 AM
Originally posted by Donn:
McFeely's bronze specs:

Nearest applicable ASTM number...B99, B105
Type number...alloy 651
Yield strength, 0.5% extension under load...70,000psi
Elongation in 2"...10%
Shear strength...50,000psi
Tensile strength...100,00psiAll of the above is WAY stronger than the steel we use. We build a whole lot of stuff out of 36 ksi material and when we have to, we go to high strength steel at 50 ksi. For pins that can't break we use 90-120 ksi material. If bronze screws break, it isn't the material's fault. More like the manufacturing process. Or, like a lot of suspect "marine" plywood, the material and the manufacturing isn't up to snuff.

12-12-2003, 10:11 AM
FWIW, I contacted Standard Fasteners in New Bedford and after going through "twenty questions" they told me they only sell to large users and I would have to fax my order with company name on letterhead. They quoted me only a $5.00 better price than McFeeley's on an order of 1000

12-12-2003, 10:44 AM
Better than $5 more, eh? You're probably very close to the bone price wise.

Did you ask Hamilton Marine or Clark Craft Fasteners for a quote?

12-13-2003, 08:07 AM
I decided to just order from McFeeley; I am looking for #10-1 1/4" and they are all about $115-120 per thousand.

12-15-2003, 05:09 PM
Good to know the specs of the alloy that MCFEELYS screws conform to, as well as Donīs(metallurgistīs)general comments in regard to these.

Does someone know the specs for the bronze screws on sale at the other suppliers such as HAMILTON MARINE, CLARK, JAMESTOWN etc. ?

If so, publish these on this Forum, in order that we may know in advance of future procurements.


Bruce Hooke
12-15-2003, 06:00 PM
So, if I'm reading those specs from McFeeley's right, and Don's comments about metallurgy right, it sounds like McFeeley's bronze screws are on the brittle side, no?

12-15-2003, 06:17 PM
Seems unlikely that Don ( metallurgist)purchases screws from McFeelys as they do not seem to fit his "lower tensile strength, but more ductility" requirement.

It would be beneficial if he could share this information with the Forum.

12-18-2003, 12:26 PM
Sorry I haven't gotten back to you sooner. I haven't purchased from McFeeleys, but that is because I wasn't aware of them when I last purchased screws. I do my own testing on the screws I purchase so I can be sure of what I'm dealing with. I prefer 416L stainless, because it seems to be more readily available and cheaper. But the boat I'm building will not live in the water, so I have the option of using SS instead of bronze.

Anyway, the strength versus elongation issue:
There are two generic classes for material macro-behavior - ductile and brittle. Ductile is more resilient than brittle, meaning you can load it to a certain point and when you release the load, it will return to its original size and shape, no damage done. Brittle materials behave less so. You load them a point, and they either crack or they don't. There's little "give" to brittle materials. Ductile materials pay a price for being springy though, and that price is strength. Brittle materials are generally stronger than ductile. But ductile materials are TOUGHER than brittle (it gets a little confusing here). Toughness meaning "resistance to fracture", as opposed to strength meaning ultimate tensile strength (UTS). Think of it this way, you can apply a bending load to a pencil eraser, and it will bend accoringly with developing a crack (to a point). When you release the load, the eraser returns to its original position. Try this with the pencil itself, and it may snap if enough load is applied. While it takes more load to break the pencil (strength), the eraser is more ductile (tougher).

I would think that most fasteners are made of ductile material, because brittle materials are very sensitive to stress concentration points, such as thread roots. Elongation is a measure of the relative ductility of one fastener as compared to another, so when I said I would sacrifice a little strength for a little more ductility, I was speaking in terms of relativity among fasteners. I had a batch of screws in the past (SS again) that seemed to all snap below the heads if I hadn't pre-drilled the holes, and I've had batches of supposedly the same variety that didn't exhibit this behavior. It's an issue of relative ductility.

Sorry this is long. I get going sometimes.

Best of luck,