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I bought some "brass" wood screws yesterday at a local hardware store and they were bending and breaking off in the hole. I compared them to some brass screws I had ordered from Fastenal, a commercial supplier, last year and the hardware screws were lighter in color.

Brass screws are supposed to be made of "high brass", 65% copper, 35% zinc. Is there a chance I have a substandard screw with too much zinc in it, or am just being paranoid and the lighter color is because the screws are newer?

Is there a way to check the screws to see if they have the right composition?

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    Brass screws are notoriously weak, much weaker than steel screws. I guess that is why you can buy "electro-brassed" screws that are steel with a thin electro-plating of brass. Is it possible that this accounts for what you experienced? – RedGrittyBrick Oct 1 '17 at 23:07
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    Brass screws are very prone to breaking off when driving them. Typically when you're using brass screws you should pre-tap the hole by driving in an identical steel screw, backing it out, then installing the brass screw. Also it can help to lubricate the brass screw with wax. – SaSSafraS1232 Oct 2 '17 at 16:02
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    @SaSSafraS1232 Indeed, many hinges and similar hardware come with a single steel screw for exactly that purpose. – mmathis Oct 2 '17 at 20:54
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    Also, don't use an impact driver on brass screws. Don't ask me how I know... – grfrazee Oct 3 '17 at 13:59
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I'd say it's possible the composition and hence performance is different, but I don't think that's the only factor. Where I work (at a commercial joinery making windows, doors etc.) we go through thousands and thousands of screws per month and I can tell you that 99% of the screws that you get are rubbish - just generally poor quality, easy to snap, soft heads which round out etc. and even screws which claim to be made from the same stuff, by different makers, can vary wildly in terms of performance.

Generally I would say if you find one make of screws which works for you, then stick with it. Even if the material composition is the same, I believe things such as heat treatment/how they are formed can affect the performance. I'm no metallurgist but cold-forged screws seem to be better for at least some alloys as I think the metal "work-hardens" and becomes stronger through the forming process.

If you're looking for good strong screws then I recommend Reisser R2's if you can get them, but these are not "pretty" screws which you might want to leave on show. They are super super strong through - hard to round out and they almost never snap unless you screw in and remove the same screw repeatedly.

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Not the screws; your pilot holes and clearance holes were not big enough. Brass is only about 50 % the strength of steel and things like steel deck screws are even stronger as they are heat-treated. Brass ( yellow) is normally 60:40 or 70:30 ( sometimes with 1% tin) ; the strength is more a function of cold work than alloy- your problem has nothing to do with alloy.( On checking I found alloys from 95 Cu: 5 Zn ,to 60 Cu : 40 Zn) Many fasteners have rolled threads which cold works to higher strength .BUT the tapered threads of a wood screw don't work with rolling. Brass screws are( typically) made by cutting cold drawn bar. But cold drawing hardens the surface more than the core, so you cut off the hardest material. If you cold head then cut threads you have a stronger head but the same low thread strength.(The tensile strength of brasses can be from 40 ksi to 80 ksi depending on if it annealed or fully cold worked . Ordinary cold rolled steel would be roughly 80 ksi )

  • Interesting footnote : the 70:30 is more yellow than the 60:40 .Aluminum bronze and manganese bronzes are a whole different story although about the same color. – blacksmith37 Oct 12 '17 at 1:05
  • Not really on topic for the question because he had a difference between two types of "brass" screws? – WhatEvil Oct 15 '17 at 18:08
  • The exact composition has little or nothing to do with the strength for these materials. It is all the cold work. – blacksmith37 Oct 16 '17 at 22:55
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I think you are using them too roughly. As SaSSafraS1232 said in a comment, you should always screw in a steel screw of the same size and shape first (but it can be a Posidrive/Torx rather than slot head), and then drive in the brass screw by hand.

(The steel screw can obviously be machine driven)

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