Tuesday, February 9, 2010

Going Overboard

When relying on screws to support a lot of weight, I tend to go overboard and use more than necessary. Call me skeptical, but I'd rather play it safe.

My dad, a retired nuclear projects engineer, told me about an experiment he and other students conducted in his college's shop class where they calculated and tested the strength of rivets using the knowledge they acquired in strength of materials courses.

They hooked a chain through the license plate holder of a '43 Ford. Dad remembers the details about the car because 1) he's an engineer, and 2) he's a dude.

The two 1/4" rivets of the license plate holder supported the car as the students used a hydraulic lift to hoist the front end about 7" off the ground. They came up with the idea for this experiment because 1) they were dudes, and 2) they were dudes.

Granted, rivets and screws aren't exactly the same thing, but I remember that car experiment every time I use screws for support, as I did when hanging my hand tool cabinet. Despite my Dad's left brain wisdom, I still sank about 30 screws into the French cleat on the back of my cabinet for fear that it would otherwise crash to the ground. The mating cleat is secured to wall studs with 6" lag bolts.

Overkill? Maybe. But I do this every time I use screws because 1) I'm overly cautious 2) I've heard enough ideas-gone-bad stories from my dude friends to question the results of their "experiments," and 3) learning how to calculate screws' tensile, shear, and compressive stress levels is about as interesting to me as watching a fresh coat of paint dry on a restored '43 Ford.

The following video illustrates my method for hanging a small family portrait. It enlists the help of a backer board in the event that you have trouble locating a stud. The stick figure is meant to be pulling a cordless drill out of her pocket, but I realized after watching the video a few times, it looks a little...odd. Ah, well.


JimK said...

Good One Kari

gchpaco said...

That's still not an unreasonable thing to do, considering that screws are different from rivets and bolts. Screws have a tendency to pulverize the wood they go into, the wood itself is not exactly regular, etc. If you could get access to both sides and bolt it together, like mechanics can, then you can start talking about strength-of-materials courses, but there are so many variables with screws that it's hard to say what would work.

That said, 30 screws is probably overkill :) and could possibly have weakened the cleat or cabinet (although I suspect you would have found out about that by now). You could probably get away with 8 if they were the right screws (i.e. long ones).

will said...

An architect friend likes to laugh about about how people waaay over-do wall attachments. I'll tell him about ou!

Anonymous said...

So.....my 401k's have tanked for the last two years....the economy stinks......now I know where I am transferring my investments....

What brand of screw do you use again? :)

As always, love the post.

Dave B

Brad Ferguson said...

fantastic animation and Love the Munster's homage, keep making me laugh please.

JERM said...

6 inch lag bolts?! Have you gone to the other side of the wall to see if the lag came through =) Seems to be handy place the stick figure keeps the drill =)

msiemsen said...

Kari, A single 16 d nail will hold about 200 pounds. I was hanging cabinets in a house and the resident teenager doubted that the 2 screws I hung the cabinet were enough to hold up their dishes. This cabinet was just big enough for me to climb into-so I did. He decided it was strong enough. My father was re-roofing a large gothic roofed barn with a crew of guys. One of them didn't think there were enough nails holding the staging so he banged in some more before he went up on the roof. The additional nails weakened the scaffold and it collapsed, no one was hurt but my father was very annoyed with that fool. This all depends on the length of the screws but 4-3 1/2 inch screws would hold a lot of cabinet.

Paul Lapczynski said...

The points about too many screws will make screwy!

How many screws/fasteners would it take to weaken a board, one every inch, two inches,... Seems like a good Popular Woodworking article.

Now this will drive you nutty and screwy for sure. If you were organized, which I am sure you marked a straight line on those french cleats. I would also bet that you picked a fairly nice straight grained piece of lumber for your cleats. Since they are all in a row, could you have just caused the cleat to split right down the screw line?

Soon you will be measuring the cabinet for distance from the floor and ceiling to see if it moves over time...

Seriously, loved the article and the blog! Thanks for doing it.


Jeremy Kriewaldt (jmk89) said...

If you are screwing into wooden studs (the language of building is lascivious isn't it), the issue is the gauge of the screw and the depth that it goes into the stud. As you know, I am lazy and drilling three holes is 50% more work that drilling two holes, so a bigger hole and a bigger screw is worth it to get out of that extra work. The trick is to make sure the hole is the right size to engage the treads of the screw to the greatest degree without interfering with the shank (which just makes it harder to turn the screw!).

As always Charles H Hayward comes to the rescue. He wrote a book (Handyman's Pocketbook, ISTR) that tells you what you need, so you don't have to do the calculations.

My experience is that screws don't break, they tear out (or in masonry situations, they pull out the plug ), so the trick is to ensure maximum engagement between the screw/plug and the wall - the right size hole and a big enough screw, is all you need.

Darnell said...

Take that, Pixar!

Dennis Cloutier said...

Thanks, I needed that.

By the way, safe is better than sorry. We used to have a ladder hanging from the garage ceiling above my wife's car. The screws holding one of the brackets pulled out and dropped the ladder on her car. On her Porsche Cayman. This was not good.

Kari Hultman said...

Thanks, Jim!

Gchpaco, every time I add a new tool to the cabinet, I wonder if it's the straw that will break the camel's back. haha

Bill, be my guest! :o)

Dave, I was thinking the same thing. ; )

Brad, glad you guys like the stop animation. It sure is fun making the videos.

Jerm, they were 5" or 6"--I forget. But my builder used 2 x 6 studs, so it's all good. It did take a while to tighten them up, though!

Mike, I totally hear ya. I know my kitchen cabinets, which are filled with heavy dishes, are only held in place by a couple screws.

Paul, you're right that this would make an interesting article. Fortunately, I know not to put screws and nails all in one line. whew!

Jeremy, sounds like I need to get ahold of that book by Charles Hayward.

Thanks, Darnell!

Dennis, oooh, that had to have hurt! And I bet the car was in bad shape, too.

Dave said...

For the life of me, I can't remember which magazine it was (FF? PWW? AWW?) But someone did do a test of plywood carcass construction methods and strenght. What they found was reinforcing a glued joint with screws did make it stronger, but having less than 8" between screws seriously weakened the material and it would fail. How that applies to construction grade studs, dunno.

On another note, screws and nails are usually graded in strength in two applications. One being a straight pull out from the material it's in. The other is a shear force pulling at 90 degrees to the screw or nail. Now granted that screws are much stronger in a direct pull situation, but the shear numbers are close. Although screws still win out. But again, in a shear application, each screw will hold a few hundred pounds. With that in mind, your 30 odd screws should be able to carry around a ton or two. Literally.

Gary Roberts said...

A. That animation is the funniest darned thing. Luckily I wasn't drinking orange juice when watching it.

B. Lag screws, sometimes called lag bolts somewhat erroneously. Or was it Moses who supposes, erroneously? Anyhow. When hanging something heavy like a tool cabinet, go for lag screws with washers and forget those piddly little screws.

Anonymous said...

I hate to go all statics and strength of materials on you. Statics will tell you how forces will act on the joints in your cabinet. You need to look at where your joints are in the part you are going to use to mount the cabinet and then see how the load will be passed to other joints. Using 2 screws instead of 3 may cut your install time by 1/3rd but could put forces on the cabinet that pulls its self apart. One trick is to angle the screws like you would a nail in a picture hanger. This causes gravity to "pull" the cabinet to the wall and reduces tension on the screw.

The other issue which has been over looked is the shear stress areas put on the cabinet by the mounting process. When you drill a hole to mount a cabinet, you introduce 3 areas of possible stress failure on top of the failure of the screw in shear. The hole itself could deform. The material behind the hole under load can break. And the holes in the plane perpendicular to the load can break.

The good news is there’s math that can give you the answers to these issues. The bad news is most of the formulas contain more upper and lower case Greek letters than Latin letters.

Also, since your cabinet is indoors, you don't need to worry about thermal stress and deformation, though if the humidity of the house changes, similar forces can be introduced in to the wood. But there's more math to correct for this issue.

John Cashman said...

Wow, there's a lot of "Dude" responses here. I just like cartoons.

Anonymous said...

Yeah, we get it, you hate men, keep reminding us lest we forget.

Furthermore, there is no such thing as a 1943 Ford. Ford switched over to war production in 1942 and there weren't any more automobiles produced until 1946. The model year 1942 was the last prewar Ford car.

Kari Hultman said...

Dave, sounds like my tool cabinet won't be crashing to the ground anytime soon. Probably less screws would have been better, though.

Gary, a guy at the hardware store argued with me about lag screws vs. lag bolts one time. He INSISTED that they were called lag bolts and stormed away from me when I said I thought they could be called either. Anyhow, I call them lag bolts now. ; )

Michael, next time I need to hang something heavy, I'm contacting you first! :o)

John, glad you like the cartoons--I like making them. :D

Anon, did you have a bowl of nasty for breakfast?

Anonymous said...

No more than you have every day.

Seriously, you expect us to take you seriously and you refer to a nonexistent car, and keep making "dude" remarks.

Were I writing a blog I wouldn't disparage half of the population of the country just to reinforce a set of prejudices. It doesn't make sense to keep writing anti-male sentiments here. Think about it.

Anonymous said...

As a fully red blooded dude who likes guns, tools, cars, and experiments, I approve of this blog post!

Anon, seriously, life is way too short to be that cranky. Take a breath, realize how good your life is compared to most people in the world, and find something to laugh about.

Justin Tyson said...

I'm a dude, and I approve this message.

Loved the video Kari :)

Larry Marshall said...

It's worth noting that "Anon" says "IF I wrote a blog..." (he doesn't). It's also interesting that he reads your blog even though he doesn't like you, Kari. That he won't let us know who he is underscores all else.

Sometimes a comment says more about the messenger than the receiver of the message. I think that's true here.

Thanks for your great blog.

Cheers -- Larry "A proud dude" Marshall

Kari Hultman said...

Thanks, Scott, Justin, and Larry. Anyone who knows me knows how much I love my dude friends—guys who pride themselves on always having a funny "experiment" story to share. If anything, I'm cutting on myself for always using waaaaaay too many screws. Guess that makes me a misogynist?

Anonymous said...

I do enjoy life, laugh, work, and have fun. But I object to anyone thinking they are entitled to take broad swipes at groups of fellow human beings without being called on it. Kari repeatedly displays her bias against men here, especially rural white men, and she needs to be told that that is not acceptable.

I am sorry that Kari is content to keep blasting men, but that's her problem, not mine.

Carry on - even though it is cold I am going out to the shop and make some chips.

presbyfruit said...

Kari loves men. She has hundreds of male friends and only a few female ones.

rgdaniel said...

Munsters = Awesome.

Anonymous = Lame.

Mattias in Durham, NC said...

I would definitely call it overkill if your lag bolt pokes through the other side of the wall.

will said...

Hey Anonymous, Dude, are you one of those dudes; who sees dirty pictures in cloud formations or in a glass full of ice cubes? Dude, are you hearing tiny voices coming from doorknobs and turkey sandwiches?

Dude, the way I see it, you're picking a fight over a nonexistent issue. Maybe you should vent your workshop there might be some toxic fumes from out of date chemicals in there.

Oh, and by the way dude, if you don't care for Kari's blog, don't read it ...

Bob Easton said...

Fabulous video!!! Now we know what to do when it's too cold in the shop, make animations.

FWIW, if you really detest guys / dudes that much, why did you draw a stick dude instead of a stick gal?

Kari Hultman said...

Thanks, Bob!

Mattias, maybe that's why the siding on my shop that's opposite my tool cabint is popped out a bit. ; )

Bill, your turkey sandwiches don't talk to you?

Bob, that IS a stick gal--didn't you see the curls? haha

Tom said...


Great video. It does remind me of an old 'Life in Hell' cartoon titled 'If you drink, don't drill'; though your character actually gets something done.


Vic Hubbard said...


I LOVE your cartoons!! I just watched it again with my 3D glasses from Avatar...WOW!!! Scary when that drill gets pulled out!

Regarding Anonymous, Has no Life, Seathing with Hostility Dude; While I get a twisted kick out of seeing someone get all spun up, since he comes in anonymously and I, therefore, have no "face" to put with the idiocy of his statements AND his statements add nothing to the post, could you please just delete his input? I'm sure he has plenty of other people he hates enough to go heckle.

Kari Hultman said...

Tom, I remember that cartoon!

Vic, so far the only comments I've ever deleted were spam. But as a friend pointed out, comments that are just mean-spirited and serve no purpose should be deleted since they just waste readers' time. I'll start deleting him from now on.

Charles "Sunshine" Davis said...

Yeah, your stick figure videos are simply the best. Love 'em.

I totally did not expect the stick figure to give birth to a drill.

I, too, tend to the over-cautious side with fasteners. It's all good... just don't lean on my walls... there's not a whole lot material left holding them up!
-looking forward to more awesome cartoons!!!!

John Cashman said...

I feel bad that a J#@$%ss feels the need to attack you Kari. I do hope you ignore him. I think I smell a cartoon chef.

Anonymous said...
This comment has been removed by a blog administrator.
Kari Hultman said...

Yep, that comment that was deleted was our Anonymous bloke. Anon, you are wasting my readers' time. Be gone.

Anonymous said...

Kari spent her young adulthood in an era when attacking and suing all things male was cool and politically correct.

Having read some of Naomi Wolf's work, it's not surprising that negative oriented words towards males would be part of a 40 something female lexicon.

I just wish they didn't kill the Snap-On pin up calendars.

Anonymous said...

Now that you deleted Anonymous bloke's comment, I look like an idiot.

rgdaniel said...

I've been known to be hypersensitive to criticism, but I don't see how calling us "dudes" and pointing out our fondness for tool use, which we now share with "gals", can be construed as offensive.

I say CAGE MATCH, Kari vs Anon... as a dude, I'm supposed to love bloodsport, right?

Kari Hultman said...

Michael, the only idiot who's ever visited this blog is the one I deleted. Sorry about the pin-up calendars. ; )

Bob, we could call it "Woodworking...Beyond Thunderdome!"

Mattias in Durham, NC said...

@rgdaniel: I agree. Something must be wrong with that dude. Maybe he is insecure about his dudeness. Does that demote him to just a dud?

rgdaniel said...

LOL @ "Dud"... B-)

Bob Easton said...

With Anon no banished (idiot!), maybe we can get back to serious business...

You're great with tutorials Kari. How about a tutorial on how you do the animations? ... or at least a short list of tools. (We're all tool geeks aren't we?)

Kari Hultman said...

Thanks guys. :o)

Bob, the animation is very simple: draw your first picture, lay another sheet on top and draw the next one. You can see through the sheet well enough to know where to draw the next movement. After all your pictures are drawn, make and L-shape with two boards. This shows you where to position the drawing. Set up your camera on a tripod and shoot each drawing one at a time. Bring them into iMovie, add some music, and voila! I doctored a few in photoshop beforehand, though, so I could add the Munsters' photo.

Thanks for the idea for the blog post! Indeed, let's get back to talking about our hobby.

Bob Easton said...

Thanks Kari. It was the production tool I was curious about. iMovie; OK.

For those of us who don't even eat apples, we'll have to cope with something else. Speaking of, Windows Movie Maker is the coping saw of the Windows world; erratic, wandering off on its own, and breaking just when you need it.

(BTW, since you're always good at responding to every comment, don't feel compelled to respond to this one. Go do something better with your time, like make stuff.)

Joseph Pritchard said...

Coming in late to the discussion... I too worry about wall anchoring heavy loads. I used to use drywall screws and then I read that they are prone to snap so I now use real screws, lots of 'em.

Kari, the movie is hilarious both in intended humor and um.. unintended. Your description of sequential drawings made me smile, remembering school hours spent drawing movies on the page corners of my spiral notebooks. I'm going to have to try this myself.


proud Dude friend of Kari's

Kari Hultman said...

Thanks, my dude friends. :o)

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