Consider Screws – Paul Sellers’ Blog

In my recent faux pas screwing a dovetail together on a Facebook post my goal was to prove a variety of things we woodworkers supposedly ‘know‘. What was greatly evident, and I knew this to be so, was how judgemental humanity tends to be and worse still just how self-righteousness manifests itself in the criticism of others in words such as “you should never . . .” Of course, when it’s our work we can screw, nail, dowel, plug and use any secondary fastener we want to if indeed we see fit to. It’s up to us.

I wanted to tackle the idea that we should never screw woodscrews into end grain when I venture to guess that 50% of the screws we drive or indeed I drive go into end grain. My early experiences of driving screws was in the pre-battery-driven drill-driver days of the early 1960s when all we had was flat-head screws. We mostly used the Stanley ‘Yankee’ screwdrivers to drive screws in quick succession but not generally on high-quality work for fear of slipping. If the bit slipped out of the slotted screwhead the work could easily be ruined in a single push. It wasn’t too much later before the cordless drill-drivers we know today came into being and of course, everyone liked the progression they made from 12V to the ever-more compact 20V versions we rely on now. The main advantage of single-handed use, combined with magnetic bit holders and posidrive screws gives even greater advantage when we assemble different projects with lots of screws to drive. Of course, the main advantage of power at the elbow has led to a certain loss of sensitivity when we drive the screws deep into the wood. We tend to set the beast at maximum speed and torque. But it’s this that mostly leads to stripping out the wood thread when we drive the screws home. As soon as the head hits and seats our full-power setting does one of two things; the head snaps off and leaves the threaded shaft in place but not pulling, or the thread strips out of the wood itself and there is no ‘bite’ left in the wood. Another development in screw-making further exacerbates the problems we face. Self-drilling screws with hardened shafts are indeed harder but also more brittle. They may not buckle under the pressures of being driven but they do snap more easily. Added to the self-drilling aspect of the centre point is the serrated edge to the thread itself. Each advancement may be an improvement but only under ideal circumstances. There can be no question about it. Unlike one commenter saying, “They don’t make’em like they used to.” Screws are highly developed sophisticated versions to what they once were. They are cheaper now than they have ever been and just about everybody you or I know has a pretty decent cordless drill driver hiding somewhere in their shop. I think woodscrews are absolutely amazing inventions and they are better than they ever were. By saying all of this I am explaining that it is not the screw going into end grain that is so much the problem but the user with so much power at the elbow displacing the sensitivity we had when we indeed relied purely on our own strength.

I think it is twelve years ago since I made this bench stool. Though I never actually intended to use it, I have indeed used it every day since it came together purely as a prototype to test for angle, stability, height, etc. It became one of those ‘cobbler’s children‘ things. This stool version was made from two two-by-four spruce studs ripped down to thinner sizes so very soft and not particularly ‘good’ wood for resilience. Had I listened to the naysayers I would not have had twelve years of use from the stool. I’m guessing that this stool could just about see me out if I do indeed live using it until I am 100. Who knows?

I painted the stool blue with a white undercoat for appearance. I used two screws to the ends of each rail and predrilled every hole with stepped holes so that nothing was forced, over-drilled or oversized. I can drill slightly undersized by a fraction so that the screw employs an additional friction hold as well as the threads. I hasten to add here that I m not saying the end-grain screwing is as strong as the side-grain screwing, I am not, but I am saying we should not shun this as a viable option in some if not much of our work. It will depend mostly on what we plan to use the project for. And remember that we can compensate further by using longer screws where the wood allows for it.

Above is a more recent stool we use in the classes for students to use. That’s a day or so a month if that. It should last for a hundred years at this rate of use compared to my blue version. I am in no way suggesting pocket hole screws for furniture making nor am I saying screwed-together pieces are a good substitute for proper joinery. I hate even the term pocket hole joinery; that’s the exact opposite of what it is. But there are times when time disallows the full monty. Many of my prototypes are simply screwed together to express a concept and to save time, energy and money. There is nothing wrong with that.

The extremes in woodworking often remind me of the extremes in religions through the ages, even into our present age. The word legalism comes too regularly to mind much of the time. We do tend to want something of a religious demand on precepts and concepts like the angles for sharpening bevels on edge tools or dovetails. In my world, I work somewhere between 20º and 45º depending not on mood but wood type, pressure applicable to task, angle of presentation and much more. The law of thirds seems just silly to me in the same way never screwing screws into end grain is silly or believing that a dowel is stronger than a screw when I want the pulling power of a woodscrew.

Here was my experiment today. It took me ten minutes and I felt it was worth the doing. I made a mock door frame, hung a two-by-three spruce stud from the opening two inches above the floor by a single screw into end grain and stood on a step piece I had screwed into the end and into the end grain. I tried it three times stepping off a two-inch high board so I could get even pressure to each side of the stud. I weigh 75 kilos (165 lbs) `and the screws top and bottom held fine even in ultra-soft spruce. There was no glue. These interesting experiments bring enjoyment to my work with you. In the Facebook post on screwing the dovetail, it was the legalism that I know we are all capable of. Questioning authority, the concept, likely originated with Socrates, but there was much questioning taking place in the 1960s when government used manipulations and machinations to control people into thinking bigger numbers of people suggested the right path would always be taken by the majority. In the few comments countering my desire to use a screw in the middle of my dovetail, there were 12,000 likes and a couple of hundred criticising the use of the screw. My wooden bench stool prototype has 32 x 3″ screws holding the angled butt joints together. How that translates into the applied pressure to each screw with 75 kilos (165 lbs) I’m not sure. The pressure on the stool screws are never direct pull as in my experiments on the dangling stud. Maybe in this article, I am asking other questions such as why go to the trouble of good joinery when screws will be good enough. Why take so much time hand-cutting joints that take days when in an hour or two you can have a stool together and in use? None of this really, more that there is a place for prototyping pieces and skimming off the top to get something together. End-grain screwing is good in my book as long as we are responsible for where we will use it. We must consider one thing that screws really don’t take care of and that is the constancy of expansion and contraction. I will never be an advocate for screwed-together furniture. That’s just lazy and never a good substitute for good joinery in well-made pieces.

In all of this, I in no way want to discount the reality that screwing wood screws of the correct and appropriate type through and into face grain is not much stronger than screwing into end grain. It is considerably stronger in 95% of woods and wood types and that difference is not in any way questioned. So many things become legalistically imposed on others as do’s and don’ts rather than to consider more the appropriateness. In the case of my dovetail and the reasoning behind it was a perfect solution.

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