How deep into the wood should a screw go?


Just a quick question and forgive me if it annoys you, how deep into the wood should a screw go? A 1/3 of the width of the wood? 2/3s?
Thanks and many regards.
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snipped-for-privacy@gmail.com wrote:

Wouldn't that depend on the thickness of the wood? Wouldn't it depend on what is being attached? I can't think of any "one size fits all" answer to your question.
Dave
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wrote:

The correct answer is "deep enough".
All depends on what you're screwing to what. You're looking for a one size fits all answer and there is no such thing.
Joe Barta
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snipped-for-privacy@gmail.com wrote:

You mean thickness? The standard solution is the screw should be 3 times as long as the thickness of wood piece it hold. Often not an option.
Maybe you are asking how deep can you screw it without a bulge in the wood. If so, and you drill pilot holes, the screw tip should stop about 1/8" to 1/4" from the wood surface that is visible and to be finished.
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Most screw manufacturers say 1/3 of the screw in the top piece, 2/3's of the screw in the bottom piece.
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snipped-for-privacy@gmail.com writes:

There is no single answer.
Some times when I want to mount a flat board to a faceplace for my lathe, I use 1/2" #10 screws and shorten/sharpen them so the strength increases while the requirement for penetration decreases. (This was for a design where the side with the screw holes is never seen). The shorter the penetration - the more usable wood I end up with.
I can give an example where the longer the screw - the better.
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Bruce Barnett wrote:

Argh I'm new to woodworking, I don't know the terminology, so bear with me please.
I'm making a freestanding shelves unit. I'm using shelf boards that are sold per piece, and then I'm using two rather thick and long pieces of timber (I think it was 5cm x 8cm x 2.4m) so that I would make it stand upright and then fit the shelves on it. To do that I'll be using those L-shaped pieces of metal. Two for the two pieces of timber to make it stand and not fall on its face, each one of them (the metal L-shaped things) will be ~30cm, facing away from the wall - the shelves will be standing against the wall but not attached to it. Then I'll use smaller pieces of those L-shaped metals to attach the shelves to the long pieces of timber.
My question really is about the two long pieces of timber, when I attach the L-shaped metals to them on which the shelves will rest (and will be screwed, but I know I'll just use 12mm screws for those because the shelves will be 20mm and will rest on the metal anyway), how deep into the long pieces of timber should the screws go to make sure the shelves don't fall off, and how long should I choose the screws to be? Should they go a 1/3 of the way in, or 2/3s?
I should say that I'll be using the shelves for books, so I expect that they'll have to bear some weight.
Many regards and thanks.

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---<| screws are measured from the very pointy end of the tip to the flat end on the fartherest side ---|) screws are measured from the very pointy end of the tip to the flat on the underside. Same with machine screws, and lag bolts I believe. generally in 1/8" increments, so don't bother looking I constantly trim the ends off with a dremel for max penetration. Tip rarely matters. Pre-drill is often needed the deeper the better, esp. in end grain, mdf, particle board. I'm not happy if I'm more than .020" away. About a 7 pieces of paper. In machine screws fine threads are stronger than coarse, e.g nf>nc. when push comes to shove, add more depth rather than force width wood screws come in numbers #8 is commonestly, 6, 10,12, 4, 14. smaller is smallerestly simialry sizes use like screwdrivers they come in silver, gold and black Gold ones snap, esp. the small ones. Don't use these. Black ones rust. Don't use these either.
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when they get longer the increment changes to 1/4", then 1/2". Don't look for those.
The length of the unthreaded shoulder just undre the head is designed according to an ancient recipe of a max of 1/3 third the shank length or a minimum of n inches or whatever. Don't look. Sometimes it is better to buy a shorter screw with more thread. Don't ask. and definelty don't ask about washers.
The radius on the underside of the head of machine screws is controlled to a very high tolerance also. In metal to metal contact m/c screws should have calculations made such that enough threads are engaged so that the tensile strength breakage point is converely supplemenatry.
The coefficient of friction, , of a titanium and carbon or low allow steel, but not corrosion resistant steel between a nut and a bolt is .08 (+/-20%)
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Take a look here for good screws and a wealth of information that may be contrary to your terminology and way of thinking.
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Color really nothing to do with material a scew is made of. You can get black and gold steel or black and gold aluminum and the black steel and black aluminum will behave quite differently. You have to check for the material they are made from. Stainless steel is less likely to rust than galvanized steel and both are less likely to snap than an aluminum or brass screw.
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Better questions bet better answers. That is a much better question.
20 or 22mm. Go as far as you can without coming out the other side.
Wood screws have a tapered profile and their bite come from the thread (or depth there of). Since the very tip of the screw (the first 4mm (1/4'")or so) is narrow the threads can't be to deep and it can't get much bite. What I am saying is that the 1st 1/4" of screw doesn't give you any significant holding power.
If your screw is 2 inches (5cm) long that's not really significant, if your screw is 10mm, that's nearly half your screw.
As others have said, it's tough to comew up with a simple rule.
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On 24 Feb 2006 19:27:10 -0800, snipped-for-privacy@gmail.com wrote:

You are getting people all mesed up about a handful of screws for God's sake. Do 2/3 and forget it. If they don't work your project was doomed for failure from the start; 1/3 wouldn't work if 2/3 wouldn't. Make an adult decision.
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Fri, Feb 24, 2006, 4:35pm (EST-3) snipped-for-privacy@gmail.com doth query: Just a quick question and forgive me if it annoys you, how deep into the wood should a screw go? <snip>
All the way.
JOAT If you have something to say, raise your hand. Then shove it in your mouth.
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actually everything about any screw you can buy is predetermined. I read Machinerys Handbook. There are pages upon pages of indexes on everything you could want to know. Its a book about a book. Then its a book. There are no surprises in fasteners. Its just easier if you can just pick up one screw that ain't gonna do it and if you have a basic knowledge you can count the ways to get where you are going. You can shop at HD without moving your feet. But the calculations! You ask. It gives. Before you can ask. Its not big onn wood though, there is a bit of info. I'm not looking.
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whats really intersting though isn't recognising that there is a 1/2" unthreaded shoulder on all screws from e to f lengths, 3/8" before, 3/4" after, none here, etc. but being about to recognize where the potential breaks are. Where logic makes a U-turn - it is natural - I sold screws for a while. This Q isn't rocket science. But you bettter beieve that it is. You could literaly spend the rest of your life gathering info - and yes, you would need a genius IQ just to even think about it.
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On 24 Feb 2006 16:35:06 -0800, snipped-for-privacy@gmail.com wrote:

Depends on what you're screwing, what kind of wood you're using and how strong it has to be. For a joint that doesn't need to be very strong, you'll need less "grab" than a joint that's load bearing. Screwing into soft wood is different than screwing into hard wood.
The only real answer is "deep enough to do the job".
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Brian Henderson wrote:

I agree. Whenever I screw I bury the wood entir...err...forget it.
JP
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