One is a Waste of Money

Can you really use drywall screws for woodworking projects or should you buy the expensive wood screws? Let’s find out!.

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[IAMSatisfied]

Torx head screws cured my PTSD and allowed me to fire my psychiatrist. 😃

I'm old enough to remember the transition between straight/slotted drive screws to Phillips, Phillips to Roberts, and more recently, Torx. Each one was an improvement over the preceding drive type, but Torx is by far the least frustrating. I recall working on crews and hearing that all-too-familiar sound of a Phillips bit losing it's bite and stripping out the head of the screw. Finding a decent quality Phillips driver bits was always something I was bent on improving, and even with good quality bits, one HAD to provide PLENTY of force into the screw to keep the bit engaged AND have them aligned almost perfectly. Now that Torx is on the scene, yeah they're more expensive, but they're also saving time and frustration, and that is not so easy to put a dollar value on.

[btd]

Big problem with your testing, you kept reusing the same hole in the vertical board, the very first screw distorted the hole and made every screw after that to bend down and easily pull out of the wood. In other words, you should have used a new hole each time. See angle of screws on uprights at 3:28

[Bionicjoe]

Go watch Project Farm's video on screws & nails.
This video is how to do a bad test, and build something wrong.
If all the weight is on ANY screw or nail it's dangerous.
Fasteners hold lumber and brackets. Lumber holds the weight.

[DanielSon]

To do a fair test, you should drill new holes for each test

[thedabblingwarlock]

Okay, playing chords when you showed Dmaj and Dmin was pretty clever.

Also, I know that this wasn't meant to be one, but for a scientifically accurate test, you'd need to make some changes to the set up.

1. Use a machine to apply the load. This can be a jack, a screw, or something else. It just needs to be able to apply a consistent load to the test article.

2. Use something to measure the force applied. It should have a way for you to measure and record the peak force, since that'll be force at which you suffered a failure.

3. Try to keep from changing more than one variable at a time. There's a few things to consider here. The pilot hole, the shank diameter, the cut (geometry) of the screw thread, the major and minor diameters of the thread, the pitch of the thread, the material of the screw, the number of screws, the spacing of the screws, and the composition of the boards used to make the structure. All of these are going to affect the performance of the screws. As some have pointed out, the hole that you put the screws into was the same hole, and it was changing with each test.

4. There's a difference between shock loads, dynamic loads, and static loads. Jumping on the test rig generates a shock load. This applies a lot more force to the structure for a given mass. Force is mass times acceleration, and you're going from several meters a second to 0 in a very short amount of time.

Dynamic loads change over time. This is what you have when you gradually increase the force applied until something fails. This is a good way to test when you've hit the physical limits of a connection and figuring out how much something can hold given a specific safety margin or factor. (If you want a 2 times safety factor, you'd take the force that the structure failed at and divide by 2.)

Static loads don't change over time, but the thing is, everything is plastic given a fine enough resolution (i.e. accuracy of measurement) and enough time (on the scale of millions of years, stone and rock are very much plastic.) Applying a static load over time can tell us how the connection will perform over time. Sure, it might be able to resist a given force that's slightly less than the force needed to cause a failure, but you're stressing the wood and the screws a lot. Over time, that stress can lead to a failure as it causes the wood and the screws to deform. This is why something might hold for a while then fail suddenly even if the force being applied hasn't changed at all. Something deformed enough to change how the force is being applied and transmitted through the structure.

Incidentally, this is also another thing that is affecting your tests. When you jump on it, you're not going up to the same height above the shelf every time. It's always going to be a bit different. Similarly, you're also not landing in the same place each time, which is going to affect the amount of force you're actually applying to the screws. The further from the connection you land, the more leverage you have and thus the more force you're applying to that connection.

So, if you want to really see which is better for a given application, you'd need to change the setup to control as many variables as possible. Some things, like the structure of the boards (i.e. the wood grain, moisture content, microcracks and splits, etc.) are going to be almost impossible to control for, but you can still get a pretty good idea of how the screws perform by doing multiple tests and using statistical analysis to get an idea of how well the screws are doing even if there are things you can't control affecting your results.

The downside of this, is that it's going to take a lot of boards to do this right since each test will need to be done with with new boards that are part of the connection you are testing at the very least. Don't forget that you also have to worry about the boards transmitting the forces and loads to the connection. As you stress them, they can also change enough to affect the results of your testing.

[joelmason]

From a physics perspective, there is an incredible difference between static load and kinetic force. A more reasonable test is you adding weight gently until the joint fails. The torque of the stomping is essentially thousands of lbs vs the real weight it can hold with is a 1000 lbs.

[BiggMo]

2:08 remember the days when finish carpenters drilled pilot holes? Believe it or not, if done right, pilot holes can add strength. You’re removing the internal tension in wood imposed by just driving them straight in.

5:50 difference between #8 & #9 # 10 is approximately 8% between

[jamescaneda]

Screws work to setup but not support. Use braces, brackets, blocks, notches for support and strength.

[gregmize]

mathias wendall has entered the chat. Drwall screws are great for 90% of what I do. I've never had a screw "fail". But that's just my limited experience. For outdoor stuff I use the 3" Grip Rite #9 Exterior Screws.

[notthesnail]

Drywall screws have a bugle head, designed to gently compress drywall paper without tearing. Used in wood or sheet goods they work like a wedge and split them open easily. And in drywall screws, cam-out is a feature that every screw gun makes use of to help set the proper depth.

[billdiehl]

I started using the GRK screws and I’ve never looked back. Highly recommend them.

[ourcommonancestry]

Drywall screws are not authorized for support construction per building codes in 50 states. I.e. Joists, load bearing walls, must be construction grade or you can expect to unscrew every drywall screw and replace them or receive no reimbursement from insurance companies and building condemned by every city ordinance inspector. Fasteners (those things attached to load bearing construction) can be any material (plastic, stick-ums, drywall screws). For shelving, since they are non load bearing use joinery or brackets off the load bearing structural supports. Or just do what you want and live with the consequences... that is what I would prefer but since I so lots of construction and research building codes for every damn city i find myself in, the ordinance codes are where you want to start. Remember: Fasteners are not load bearing.

[aserta]

Screws are not for weight structure unless otherwise specified and specced for. All screws are good, it's how you use them that makes them bad or not.

[weekendwarrior]

I don't think screws are designed for holding the whole load. They are supposed to just hold wooden parts in place and the load should transfer from wood into wood.

[JeffRL]

Many sources in print and online say that choosing the correct wood screw requires having only smooth shank with no threads in the workpiece "on top" (i.e. closest to the screw's head) so that as it's tightened, it pulls that workpiece against the one in which the threads are embedded. Some drywall screws have threads all the way from the head to the tip and some only have a short unthreaded area. If there are threads in both workpieces, then driving the screw doesn't pull them together but rather moves them both in unison. Isn't that enough reason not to use drywall screws for anything but drywall?

[igelkott]

Inappropriate use of screws.
When I built shelves in my utility room, I cut 3/4" dados in the upright 2x4s and used 3/4" plywood ripped down to 2' wide for the shelves. I only used screws to mount to the wall and to hold the shelves in the dados. The weight is held by the 2x4 wood uprights. After 30 years they are still solid.

[Furyhound]

Its a game of surface area, some screws are meant to be used in softer surfaces, meaning they distribute their weight more with the shape and thread. Obviously material plays a part, but in most cases if your screws are breaking you have a different problem.

[TheJensss]

My experience as a carpenter is that there are huge differences between screws, but the price is often not a indication of quality.

Buy known brands that have a reputation to preserve, since then the quality is often good throughout the lineup.

The largest difference between good and bad screws are the corrosion resistance, and the second thing is the overall strength. Screws need to be just stiff enough, but at the same time be able to bend without snapping. let's say you have a huge snowfall or powerful winds that make some of the screws break. You will have a huge problem over time.

Since nails are rarely used anymore and we almost only use screws I buy screws by weight or in large quantities as 1000pcs boxes.

[joelcopeland]

You needed new holes for each screw in my opinion because of the enlarged hole in the back of the board where screws had already been pulled down. I think that gave the screw room to move more than a fresh hole would have.

[firefox]

Great Video, Someone may have already said this, but I'll add it anyway! For the shear force case, the diameter of the screw isn't what's important. In a shear force case, you care about the friction force between the two surfaces (Created by the screw pulling them together). That friction force is where the strength comes from. The item will fail when you get slippage and a shear force acts on the screw (Which they are not designed to resist).
This also means it's really important to create a high force between the two surfaces (Your pre-load) before the screws are put in to fix them.
If you do this test again I would clamp the two surfaces together first, then screw them, I think you'll get much better results.
For more info look up "Bolted joint design". Keep up the great work!