Is there a law of screws?

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Forum topic by Doe posted 03-17-2013 10:51 PM 2335 views 1 time favorited 25 replies Add to Favorites Watch
View Doe's profile


1403 posts in 2853 days

03-17-2013 10:51 PM

Topic tags/keywords: question screws

How do you choose a screw size? I had a 1×2 (whatever that really is) that I needed to attach to a 1” piece of plywood. There’s no load on anything (it’s for a weaving thing). What I chose was a 10 1 1/4 screw that was in a bin in the garage (I already was at the home despot earlier today and didn’t want to make another trip).

Any suggestions would be much appreciated. Thanks!

-- Mother Nature talks, I try to listen

25 replies so far

View Hybridwoodwork's profile


183 posts in 2075 days

#1 posted 03-17-2013 10:56 PM

Seems I remember something like the screw should go at least 1/3 the thickness of the second board into that board?

-- How it happened that Mastro Cherry, carpenter, found a piece of wood that wept and laughed like a child.

View RussellAP's profile


3104 posts in 2309 days

#2 posted 03-17-2013 11:58 PM

If there is no load, does it matter. What you used seems to work, go with it.

-- A positive attitude will take you much further than positive thinking ever will.

View Lee Barker's profile

Lee Barker

2170 posts in 2873 days

#3 posted 03-18-2013 12:05 AM

Russell’s got it.

There’s a ginormous array of screws out there: head shape, receiver shape, material, finish, thread, tip, shank….and on, I suppose.

Russell’s point is that there are no real rules. Experience will teach you what diameter and style will work in what woods. Yes, there may be some heartbreak along the way but it’s unavoidable and in fact valuable.

Come to think of it, there is a rule: The Baby Bear Standard!

Not too long, not too short
Not too thick, not too thin
Not too coarse, not too fine

Just right.



-- " his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

View RussellAP's profile


3104 posts in 2309 days

#4 posted 03-18-2013 12:13 AM

Always drill pilots.

-- A positive attitude will take you much further than positive thinking ever will.

View NGK's profile


93 posts in 1933 days

#5 posted 03-18-2013 12:18 AM

If a screw you used—the one you called a “10 1 1/4” should have been called a #10×1-1/4. The #10 part is the diameter—Most medium screws are #6 or #8. #2 or #3 is tiny—#10 and #12 are fat or big in diameter. At about #14 you’re getting in the zone of a 1/4-inch lag bolt or lag screw.

The other number is the length. Lengths can be from about 3/8 inch up to 3 or 4 inches. Longer than that they have special heads (so you don’t have to use a washer) or you switch to lag screws with a head turned by a wrench.

Typically you choose a screw with diameter and length suitable for the job. On many screws the shank is smooth—no threads—for about 1/3 of the lenth of the screw. That’s because you don’t need threads in the part of the screw which passes through the board you’re fastening to another board. If you’re fastening a 3/4-inch board to say a 2 X 4 you would typically want a screw to be about 2 inches long. In other words, about 2/3rds of the screw should penetrate the second board.

The diameter is relative to what most would call “shear strength”. In other words, pushing side-ways. The diameter needs to be sufficient to not shear off if someone or something pushes side-ways.

The same general rules can or should apply to nails.

View waho6o9's profile


8205 posts in 2599 days

#6 posted 03-18-2013 12:23 AM

GRK’s rock

Spax rocks as well, however, I just started using them and think they’re
better than GRK’s.

Live and learn.

View NGK's profile


93 posts in 1933 days

#7 posted 03-18-2013 03:24 AM

too bad them babies cost about 70 cents each

View Doe's profile


1403 posts in 2853 days

#8 posted 03-18-2013 09:42 PM

Thanks everyone.

NGK, the shank information is cool and makes sense (now that I know about it) and thanks for info about what they’re called.

RussellAP, I’ve learned that it’s easier (and generally straighter) to do pilots and I need to keep remembering to countersink (and countersink deep enough).

Lee, those are words to live by, and it’s easy to remember the baby bear standard.

Waho609, I’ve seen them and want them just because they look good.

It all boils down to using what’s in the bin in the garage generally is fine; I’ll eventually get it all sorted out with practice.

-- Mother Nature talks, I try to listen

View DonLumberJohnson's profile


13 posts in 1895 days

#9 posted 06-17-2013 05:13 PM

There is nothing more frustrating than meticulously milling all 6 sides of a piece of $15.00 lumber just to have a crummy 20 cent screw snap off at the head at the last minute.

I have had good results from Multi Mate screws sold at True Value but haven’t had a chance to explore their full line, just #8×1” and #8×1 1/2” both fully threaded.

The finish is much better than average and are yellow zinc, light brass color that, in my opinion, complement the seldom seen parts of a project well.

Absolutely no impression that they will snap off and with the right bit not a single one stripped out driving into birch and red oak.

With the cost of good lumber and the effort we put into our projects is seems strange to skimp on the fasteners. Not talking dollars but quality.

-- Don, Roanoke VA

View MrRon's profile


4793 posts in 3266 days

#10 posted 06-18-2013 10:38 PM

The unthreaded portion of the screw (shank) should equal the piece you are going through. If the wood is 3/4” thick, then the screw shank should be as cl;ose to 3/4” as possible.

View Dallas's profile


3599 posts in 2510 days

#11 posted 06-19-2013 12:40 AM

People actually use drywall screws for pocket hole joinery?

What a great way to ruin a beautiful project!

-- Improvise.... Adapt...... Overcome!

View RonInOhio's profile


721 posts in 2887 days

#12 posted 06-19-2013 06:15 AM

I picked up one of these nut/bolt/screw gauges. Just thought it might come in handy as a reference.

Also got a few bin organizers for screws, nuts/bolts, and misc.

Not so sure the gauge is necessary, but sorting the screws and nuts and bolts into bins seperated by size
makes it very efficient to find what you need without tearing apart the shop.

View Doe's profile


1403 posts in 2853 days

#13 posted 06-19-2013 10:19 PM

Don: Thanks for that, I’ll check for the Multi Mate screws. I may even have some; I sorted some brass coloured ones so I need to check.

MrRon: That makes it a lot simpler to decide what to use.

Dallas: It’s amazing what people will do when they don’t have a clue. I admit to ignorance and generally would avoid projects where I wasn’t sure. I must say that I was feeling pretty stupid about not understanding something as simple as screws. However, I do know what a drywall screw looks like and don’t expect to use them – ever.

RonInOhio: I think the gauge would be handy if I had strays. I sorted through everything we had and labelled them and there were a bunch at the bottom of the bin that I just threw out because I wasn’t sure I could figure out exactly what they were.

Thanks everyone for your help—it’s been most useful. I’m ready to try some joinery and think I won’t be ruining nice wood with the wrong fasteners.

-- Mother Nature talks, I try to listen

View RussellAP's profile


3104 posts in 2309 days

#14 posted 06-19-2013 10:58 PM

I keep three cordless drills for the screwing process. One is a pilot, the other is the counter sink, they always break but they still work for the bugle, and one to drive the screws. I used dacrotized and stainless steel in three different sizes which gets me by most of what I need. I buy them in bulk by the thousands and I still have half my stock after a year. Each size runs me about 40-60$ a box but it’s worth it to have the same kind of screw for everything you do. The square head is the best for not stripping the head.
I just try and remember that it’s not wise to over tighten any screw because either it’ll break or the wood will. Just snug it up and then a little bit more. Bolts are for cranking, not screws.

-- A positive attitude will take you much further than positive thinking ever will.

View NGK's profile


93 posts in 1933 days

#15 posted 06-20-2013 02:52 AM

No, Russell—It is NOT always necessary to drill pilot holes. I recently had two students make adirondak chairs out of cedar—the kind available at big box stores. To avoid rust and stain we used a coated deck screw. Cedar (and perhaps cypress or redwood) are so soft that it was NOT necessary to drill pilot holes. NOR was it necessary to use a countersink to depress the heads into the wood.

Oftentimes the black screws come in either FINE threads or COARSE threads. Coarse is for the softer woods, to avoid tear-out in the threaded area. Fine is for the harder woods, which would require pilot holes.

I disagree with another post. The is nothing wrong with drywall screws on many projects. If the appearance of the head bothers you, countershink the entire screw head in a 3/8 deep hole and use wooden plugs to cover.

I made a compartmentalized box for my typical screws as in BLACK DRYWALL and GALVANIZED. It’s about 18 inches long with black on one side and galvanized on the other. The sizes of the compartments increase for the longer screws. One side gets longer for one color while the other side gets shorter for the other color.

I’ll try to state that another way—at one end of the box the two compartments are “long” for one color and “short” for the other color. Then each box on each side gradually changes in “length of screw” until the opposite extreme on size is reached. Both max out around 4 inches.

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