On Screws For Woodworking

I am never sure if we altogether understand self-drilling screws, the need for pilot holes, and just what’s happening at the tip of the screw with its ultra-pointed, missile-shaped point. In industry, carpentry-level assembly and such, they are indispensable and an odd split in a deck board will ultimately add to the dozen or so other shrinkage and expansion cracks anyway, regardless of the screws. But it is in benchwork and finer work where the ultimate cost can ruin our work. Oh, and I know some carpenters who go to the same extremes I do to prevent or lower the risk of a board splitting because of a wrongly driven screw too. This weekend I was driving screws in the stops of my greenhouse glazing panels and a few other places too. All of my holes were predrilled. I do this on almost all of my work. I have experimented to ascertain exactly what happens within the wood. Predrilling is an imperative step for me.

On the inside of my greenhouse I predrilled holes to reduce any splitting.

Not too many people in woodworking use slot- or flat-head screws these days. It is a strange thing but when the screws are visible, slot-heads remain unsurpassed for looks. I use mostly brass screws on all brass fittings, but when a wood screw is necessary say for dismantling in a piece of work, I will look to a slot-headed version. An instance in mind also is the black-japanned round or dome-headed screws used on gate and door furniture outdoors. Somehow, the cross-headed screws never seem quite right. Ultimately, my opinion will die with me, I know that, but until then I will always have the beautiful advantage of lining up that slot with the perpendicular or horizontal axis of whatever is being fixed.

This image has an empty alt attribute; its file name is PXL_20210324_080930808.PORTRAIT-768x1024.jpg
Black-japanned screws with slots aligned with the edge for a pleasing and uniform look.

A point without pun worth making is the reality that it is not just the point part of the screw that eases access of the screw into the wood. This is only really a start point that eases the screw in, yes, but then the thread takes over with heavy force from the drill to pull the screw and the shank or main body of the screw into the wood. The sharpened and refined point with its reaming capacity does not drill away the wood beyond the first percentage of the length. The screw itself cannot remove any wood because the shank of the screw does not have the flutes that twist drill bits do, so at best what the self-drilling screw does is fracture the fibres. The wood remains within the threads of the screw and because of this, the wood is very likely to split at some point. This is especially problematic with resilient hard and dense-grained hardwoods. The denser the wood, hardwood, or softwood, the more likely the split. I think that it is important to note here that it will always be best to drill a stepped hole of lesser diameter to ease the circumferential pressure caused by the screw’s reduced shank even though the screw shank is smaller in diameter.

I ripped through wood and brass and sanded same flush to get this image showing the screw inside the wood.

Pre-drilling is not always pilot hole drilling and we do tend to call such holes pilot holes. Predrilling is not to pilot and guide the drill bit into the cut even though it does do that too. A pilot hole encourages the screw to follow a particular path and especially is this so when planning to screw into narrow edges and such. This can be important in some or many situations. The screw can and often will take the path of least resistance. It’s not at all unusual for a screw to follow a radius of a growth ring is a good example. This is especially so where the growth ring comprises extra hard and extra soft aspects to each growth ring as in almost all softwoods. Hardwood growth rings tend to be equally consistent throughout the wood. We use predrilled holes to accept both the whole shank of the screw and also the reduced diameter within the threaded area so that the threads bite into the wall of the hole. Often, woodworkers drill a smaller hole so that the screw is simply easier to drive. The problem occurs nearer to the head where the diameter has no thread and the driven screw can and will cause the wood to split.

The main shaded areas show the stepped hole boring. Here you can see how the threads bite into the wall of the smaller hole where the threads are.

Predrilling, its purpose, is to accommodate the metal either entirely, as in the shank of the screw, or partially as in the unmilled area beneath or below the thread start-line. Although we rarely if ever measure the inner, reduced diameter we do aim for closeness to size. All we really need is for there to be sufficient bite of the threads into the wall of the hole. Usually, we become adept at gauging hole sizes by eye and based on previous experience. Of course, there is nothing wrong with measuring the sizes using a gauge too.

In many of today’s production screws, the upper shank is narrower than the threaded section which increases the pulling power of the screw to seat it more deeply through lowered resistance.
Notice the serrated edges to the thread at the lower area which fractures the wood fibre.

In general, we use screws for two reasons. one, we use screws to unit two pieces of wood and, two, we use screws to attach fittings such as hinges and handles to the wood. Either way, using stepped drilling ensures that we minimise or eliminate splits in our delivery of screws. In my work, self-drilling screws don’t quite cut it even though I like them.

Before anyone writes in to comment on this screw-type or that screw-type being the bestest and mostest, that is not what this article is about. It is purely to explain why, in furniture making and other aspects or areas of woodworking, it will always be best to pre-drill almost all of your screw holes and where necessary to do them in two steps as step stages, to use countersinks for seating the screw head properly and then to rely on patience to make sure you work with care.

This compressed quadrant taken from the reamed out cutting section of the screw remained in the hole and so served to plug any fibres from exiting the hole. Interesting!

Although wood screws do look tapered along the length, they are actually parallel along the whole length from the underside of the head to the near-pointed tip of the screw. In my world as an apprentice, where no battery-driven drill-drivers existed, we predrilled every hole we made to receive a screw using either a drill bit or square awl. Not much was explained but I learned why by investigating all things in my even as I still do today. To illustrate my point, the picture below shows the difference between driving only the screw to drill straight off and then a hole bored with a twist drill bit. You can see the screw-drilled hole to the left removed almost no waste and the waste that was parted off jammed into the recessed point of the screw tip compressed the fibres as it baked with the heat generated by the screw interaction with the wood–this waste came out with the screw when the screw was withdrawn.

Every ounce of wood was elevated from the drilled hole on the right whereas you can see how little came out from the self-drilling screw on the left hole.

There is no wood fibre on the outside of the hole as nothing of real consequence was removed. This shows that the sole purpose for the drill point is to merely start the screw and sever the fibres as progress is made driving the screw. The second hole shows that all of the wood fibres are removed equal to the diameter of the bit used and this alone minimises any possibility of splitting because, of course, force is drastically minimised.

50 thoughts on “On Screws For Woodworking”

  1. – What about gimlets for pre drilling?
    – Even if one uses screws threaded on the all length, the part on the head side should be drilled to the outside diameter; otherwise the screw will not pull the pieces together.
    – When used as your drawing shows, the unthreaded part of the screw act as a positioning dowel; acting against slippage. A fully threaded screw or a screw whose unthreaded part doesn’t come in the second part will not provide this function. Non slippage then relies only on the friction between the parts.

    1. Square awls work great as long as the diameter is less than the outside threaded section. The drawing does show the stepped drilling to allow the threads to ‘bite’ into the walls of the narrower diameter. When the upper section of the screw is the same as the lower aspect inside the thread line the screw will pull the two parts together. Even so, I still prefer where possible to clamp components against one another.

    2. @Sylvain
      Honestly the average compression force of the screw is far more than enough to avoid slip, especially as you are rarely using just one screw. The bit of slop around teh screw is also not a terrible idea, and is often increased to account afor cross grain wood movement such as mounting table tops. For full pulldown with fully threaded screws, it is pretty simple trick to drive teh screw till it lfts tthe top piece, cuts the initial threads in the second, back it out the partly then redrive. The initial threads catch and pull both to task, but as Paul said using a clamp just stops the problem all together.

  2. I really only like screws for hinges, regardless of the type of hinge. If at all possible for a non-hinged screw, I like to plug the countersunk hole with a plug.

    1. Do you feel differently if screws are used for carpentry, say as on my greenhouse, where a broken pane might need replacing and undoing screws would be the least damaging? Or as in the case of some pieces of furniture like my rocking chairs where I simply screw on the rockers (which are mortise and tenoned too) because on several occasions, transportation, taking it around tight corners in a house, things like that, I can remove the rockers easily. And then there are the backs of large cupboards like wardrobes where screws allow pieces to be completely dismantled. What about wooden drawer supports inside toolboxes and such too?

      1. I should rephrase this to say this: I prefer not to use screws on visible joints for furniture. So where someone would just screw and glue when dovetails would go a long way.

        Using them isn’t a bad thing and I do too use them almost daily.

        1. Regarding plugging screws – I like the appearance of the plug.

          I did have this back fire on me for the prototype of the hanging wall shelf I made. I did not take in to consideration the movement of the wood and top rail split right off the screw. It was interesting and was glad it was the prototype.

  3. Isn’t the selling point of self drilling screws that they save time. i did recently use some old (probably 40yrs) 3″ screws. They wouldn’t drive into softwood without pre-drilling , This made me decide to always pre-drill. I do have some drills that can drill the pilot, shank and countersink in one go, but rarely use them, a bit fiddly.
    I always buy screws in bulk. I think that I now have enough to last my life out.

  4. I would say that there is a place and time for all types of screws. I will predrill for screws in a lot of places, like installing base boards, window sills, linings etc where a crack would be unsightly or affect the holding power of the screw but not when framing walls, support structures etc. When predrilling I will always use my vernier to check the diameter of the shank between the threads and countersink, but not always step the hole.

    It also depends on the wood used, a “normal” pressure treated decking board from spruce ususally is fine with not predrilling as the decking screws will have a cutting section but at the dumb joints you have to do it and also countersink to avoid splitting. Last summer though I built a deck with larch wood whoch is prone to splitting so there I had to predrill for every screw (all 2000 of them)

    When it comes to slotted screw heads vs Philips/Torx heads I agree that there is a certain visual aspect to the choice. I tend to use slotted screws in furniture and visible hinges on boxes (not to mention in wooden boats) but PH/PZ heads in simpler applications where I want to use a drill driver. Torx heads have begun taking over in contruction as they require less pushing force than PH/PZ but are less aestetically pleasing to my eye but I think this is a matter of custom as well. A little bit as a higher acceptance for Philips heads in “finer” crafts now that they are so common and have been for such a long time.

    Finding screws with slotted heads is harder and harder and often requires finding special stores that caters to professionals and they will not always allow people to buy from them unless thay have a company to send an invoice to.

    1. Have you never noticed that many boards anchored with self-drilling screws may not split at the time but often result in splits later on? It can be blamed on shrinkage and expansion but mostly it is because the wood drilled by the screw seems almost like muscle and has zero tolerance to allow for shrinkage.

      1. Indeed that is the case most of the time, especially those who aren’t taught to properly predrill. I can say from experience, I didn’t learn or know how to use a drill until I was 19. I was the only male in a house of 4. So anytime something needed fixing we were told to go outside and let the “professional” do it.

        Anyway, the first thing I learned at 19 was to always accommodate for the shank of the screw, minus a little bit for the threads. This was in a local Ashley furniture store. I knew then that woodworking was for me because the MDF or whatever they make their bedroom suites with, was of low quality and not meant for longevity as even with pilot holes from the manufacture or pre-drilled holes we made the material surrounding the screw always blew out. It was so very very frustrating.

        Alas, I do not use MDF as I haven’t found a need for it quite yet.

      2. Hi!
        I would say that it happens that boards split later on but it depends a lot on the application. A decking board made out of spruce is more likely to develop cracks in the middle of the board if using screws than when using nails (I suppose the nails have som “give” that the more rigid screw doesn’t) but seldom do they crack at the screw unless it is in the end of the board. Then both pre drilling and counter sinking is required to avoid splitting.
        When attaching joists to each other etc it is less common but mostly that is covered by plaster board or other materials so that is less of a problem, the strength is OK even with cracks. All this is rough carpentry work though and when doing finishing like putting up door linings, base boards and so on predrilling and counter sinking is a must. I even predrill for finishing nails in those cases to avoid splitting of the wood.

        When making furniture, cabinets, windows etc it is always a good practice to pre drill, counter sink and then use care when tightening the screws to avoid the risk of cracks.

  5. In the drawing, wouldn’t the threads stick out a bit more than the upper shank of the screw as is apparent in the caliper photos below?

    1. It’s a good point and I did mention this (I think). Many but not all modern screws are indeed narrow in the neck and especially those intended for mass production industries and industries like construction carpentry that rely on industrialised equipment. The traditional screws do not. The thread is cut within the stem so the diameter at the neck is the same diameter as the screw edges.

  6. Ah Paul. Yes I too love the look of the venerable slot. Not so much for a flat head but for all other shapes round head & cheese head especially. I hope like cut nails there is a big enough international following that they will never die and continue to grace fine work.

    I think Canadians are unlikely to give up our Roberston’s though. (Square drive in the US) as they are simply ubiquitous here and ingrained with our yellow, green, red, black handles for the 4 sizes common around the house. The Phillips screws generally get relegated to the recycle bin.

  7. Stephen McGonigle

    You’re not alone in preferring the cross head screw Paul, it is infinitely better aesthetically, especially if a row of visible screws heads have the same orientation.

    The cross headed screw is an excellent thing in and of itself, however it always looks ‘cheap’ somehow. This is especially true of the bronze coloured jet screws which are so prevalent.

    Regarding the drilling of pilot holes, we now have a situation whereby this is deemed unnecessary thanks to drill drivers and the aforementioned jet screws. No need for all that fussy pre drilling, when a powerful driver will render such care as pointless.

    A couple of years ago, a friend and I had to dismantle an old pipe organ in a college chapel which faced being knocked apart by sledgehammers as it sadly had no financial value. It had some lovely pitch pine timber however which we were told we could have. The whole assembly was screwed together, and when we set to dismantling the piece, we found that it had been assembled years before with greased screws in evidently pre drilled holes. We couldn’t believe how easy it was to dismantle, quickly and with no damage at all. Had the organ been wanted by anyone (sadly not the case) it could have been quite easily reassembled. We ended up with lovely wood, and several jars of quality steel screws as a bonus. I have adopted this method with much of my work, especially out of doors to allow for maintenance and repairs.

  8. And then there are form drills. I have an old set by Footprint. These cut the diameters for the thread and shank. They cut the countersink as well, all in a single operation. In addition there is a clip acting as a depth stop. This locates in one of three rings in the shank of the form drill, corresponding to different depths of countersinking. Brilliant. Except I’ve never found them very good and they lose their edges quickly. A more recent type I’ve used, has a small countersinking cutter held adjustably on the shaft by a hex screw. Another great idea, but the hex screw invariably comes loose. So I think I’ll go on using separate drills and a countersink tool. I made the latter by fixing a common countersink bit in a handle. Driven directly by hand, this gives fine control of the depth of countersinking,

    1. I do like to use these screws for throwing something out of low grade plywood together. They are very convenient on the fly.

    2. The ‘form’ drills are great but since they need to be of the correct diameter as well as close in length you tend to need quite a number if you use different lengths of screws. I used one for screwing some floorboards down. creating the stepped hole and the countersink in one operation sped the job up considerably. (I did not want to nail the boards down as the Lath & Plaster ceiling below was a bit delicate)

  9. As a professional boat builder I can attest to the pre drilling theory. Attaching a plywood panel to a white oak frame member without pre drilling using a silicon bronze wood screw would make for long days. Slotted over Reed and Prince head for cost reasons also.

  10. Douglas Wylie

    Having spent the last 30+ years in metal fabrication, I have always drilled pilots and clearance holes. I size my bit by eye, lining up the bit with the shank inside the threads until the bit covers it completely. If this were metal, I would oversize it for steel or match it for aluminum. I do the same for hardwoods or softwoods. The clearance hole is alway necessary to pull the two parts together, even when clamped. I agree with Andrew and have never had much luck with the combination drill/countersink bits.

  11. Stephen Farris

    I agree with my fellow Canadian about Robertson screws. (Nothing unusual about that: Robertson screws are more popular than ice hockey here.) They will stay on the tip of your screwdriver without using the other hand, a huge advantage in awkward locations. They are far less likely to slip and stay useable after long exposure. I would certainly prefer them for something like the hinge on a garden gate. The backstory is interesting. Henry Ford found that using them saved two hours time building a Model T and tried to get an exclusive licence to produce and sell them. Robertson refused so Ford went for the newly invented Phillips screw instead. If desired for aesthetic reasons, it would be possible to line up the orientation of the squares also. And yes, I would predrill for anything but rough carpentry work.

    1. Pozidrive screws should stay on the tip of the screwdriver against the pull of gravity – I accept this may not work for longer screws due to the additional mass.

  12. Peter Marshall

    I have built a coffee table and small chairside table based on Paul’s design. Attaching the Table lid to the base with the turnbuttons and screws is a satisfying ( if somewhat terrifying ) moment . In the videos Paul uses as self-tapping screws . Based on this blog is a traditional wood screw a better choice ?

    thanks , enjoyed this blog and all the questions / comments

    1. Traditional wood screws are generally strong and less likely to snap off under torque. Using a hand screwdriver applies exactly the right pressure too whereas in most situations I have seen when people drive them with a drill-driver they drive them far too hard.

  13. I have no qualms about using screws – in lieu of nails. Where other people use nails I use screws. I hate nails with a vengeance (and straight-slotted screws as well, incidentally. Have remarked in the past that those things ought to have been outlawed decades ago, as there are much better alternatives. Perhaps it’s the engineer in me speaking. Oddly enough, I have a several sizes of Robertson bits and screws and like them very much. Pity they never really caught on in this part of the world, I understand it’s more a Canadian thing. The Ford-explanation was interesting. Get to learn something new every day here.)

    Have always been pre-drilling, no matter how rough the work, that’s how I was taught. The extra time for preparation makes the actual assembly go so much smoother. It’s just when you see other people not pre-drilling you realize that it’s probably not such a common-sense thing as you initially thought. For me, it usually takes three steps: drilling small hole to full screw depth through both workpieces; drill a second, bigger hole through only the top piece. Finally, countersink. I do have a set of drills that does all the 3 things in one step, but, for some reason, I never use them. It hasn’t become a habit yet for me to use those, I guess.

    And on occasion, I still use a clamp if I suspect the wood might still split. A temporary clamp to oppose the splitting-action of the screw has never let me down. Finally, I always use a pump-action screwdriver for maximum sense and feeling of what I’m doing.

    When I see someone rapidly driving screws with a cordless drill without pre-drilling (and you can work very rapidly that way), I get the same sensation as when I see someone putting a tap in the drill chuck and tapping a hole in metal with a cordless drill (as opposed to using the proper tool, a tap wrench). There are just some things a civilized man won’t do.

    1. Neglected to mention that I often also very lightly countersink the *underside* of the exit hole of the top workpiece, to remove loose fibers that would prevent both pieces from seating fully.

      When using screws for screw & glue (using common PVA glue), I’ve also found out that within a few short years the screws rust through. When trying to remove the screws for some reason a few years later, you’re often left with just the top part, the bottom part below the glue-line remaining in the wood. Apparently, the PVA glue attacks the screw at the mating surface and causes it to rust, often completely through.

      Also, one reason for my dislike of straight-slotted screws is that very few people bother to get the right size screwdriver to drive or draw them, often leaving them badly maimed, sometimes to the point of making it impossible to remove them later, especially the brass ones. Just yesterday someone made a jesting remark about my large collection of straight screwdrivers. It wasn’t the first time someone said that to me. But with straight-slotted screws you get very little room for error: have to use the correct thickness and width screwdriver, or you’ll damage the screw, the wood, and, possibly, if you slip, yourself. Hence, a large collection of screwdrivers in all different widths and thicknesses.

      With PZ or PH, there are basically only 4 sizes each, in (my) practice only two: PH1, PH2, PZ1, PZ2. And yet, too many people still manage to use a PH1-screwdriver for a PZ2 screw, causing burrs on the crossed-slot. Now those raised burrs are an eyesore if ever there were one. Not to mention the possibility for cuts, injury or damage to clothes. They make screws nearly foolproof, yet….

      1. I am Paul’s age, but I remember as a child my Father complaining about something he had to work on that had Philips head screw as if it were abnormal.

  14. Antony Roberts

    Interesting discussion on screws and at least all the right things were covered i.e. greasing. What was not mentioned is the problem with slotted screws of the inadvertent slippage of the screwdriver causing nasty marks on quality work. I find that the use of a carpenters brace with screwdriver bit allows greater axial pressure to be applied whilst the increased torque that can be applied is far more controllable when trying to remove ungreased difficult screws.
    Hey, I’m retired, when do you guys get any work done!!

    1. I also use a selection of brace screwdriver bits. On occasions, I have resorted to using an impact driver to remove stubborn screws.

      1. Unfortunately screwdriver bits for braces are now extremely rare as are square ended wood bits. A poor alternative is to buy a square bit to hex adapter but the play means that does not seem to work as well and you can’t get such large sizes.

        I suppose one could buy scrap square wood bits from the second hand store and then cut eh shaft and forge or grind it into a screwdriver blade. It would need hardening and tempering though before use.

        1. I have done a bit of ‘internet research’ and it appears that you can buy flat, Pozidrive & Torx bits to fit on a mechanics 1/2″ square drive. These seem available in a variate of sizes – the largest at a quick look was a 16mm flat. You could use these with a mechanics speed brace but they only have a small swing and don’t seem to have a rotating grip on the arm part. Also the part of a wood brace that has a flatish pad to apply pressure is a rotating handle in the mechanics speed brace.

          One alternative for really tough large screws would be to use a sliding T Bar, I think you can get 1/2″ square pressure pads.

          A further alternative is that there are tapered square drive to square drive adapters sometimes available that would allow use with a carpenters brace

  15. A bugbear of mine is how frequently the use of high torque powered drill/drivers results in skewed, badly driven or damaged screws. Not difficult to avoid (I personally always pre-drill and then drive the screw slowly so it seats properly) , but lazy contractors too focused on ‘time is money’ can make a real mess with these tools.

  16. Interesting variation in views and working practices, I guess we all develop habits. I always use slotted screws – try getting paint out of a cross headed version. In renovating an old house I have just cleaned the slots of lots screws holding in various doors installed in 1800s. All screws then came out easily with help from a bit and brace. I was astonished to see all the hinges were stamped AK & Sons no 5, apparently cast in West Bromwich during the early 1830s. Pride in a humble hinge! In returning the same screws (and hinges) I greased them by rubbing on a block of soap. Job done for another 200 years – perhaps.

    I really enjoy Paul’s lessons – keep them going please. Sanity in lockdown.

  17. Paul, and all the rest of you experienced commentators – I can’t tell you how helpful it is to me, a relative newbie to working in wood, to have this kind of basic, detailed information. Your photos are particularly educational and when I take the time to let your words sink in, I understand so much more. Thanks!

  18. Peter Marshall

    When selecting a wood screw there is an array of sizes described as # 4 , #6 , #8 , # 10 …etc .. Is there a good rule of thumb for which thickness to select ( vs length ? ) when selecting wood screws for use in furniture ? I typically default to # 8 .. Thanks !

    1. These numbers in old imperial screw numbering refer to the gauge size of the shank of the screw. Not too understandable or easily calculable but when you grow up with them you simply know what size fits this type of hardware/hole and countersink by eyeing the hardware etc. I grew up with it and I do collect old boxes of Nettlefolds screws wherever I come across them simply for the single, simple groove I want for neat alignment by that final turn of the screw head, etc. I buy them from garage sales to car boots and eBay has been particularly good to me at various stages. The length of the screw is relatively inconsequential to the shank diameter and they do vary a little in diameter but only by a small fraction of an mm. So, whether a screw is 1 1/4″ long or 3″ the # for the diameter is the same. I measured a few as follows and converted them to metric but I’m sure it won’t help that much. Metric sizing does make a lot of sense though – 3mm equals 3mm in dia and so on up.
      #3 = 2.3mm
      #4 = 2.7mm
      #6 = 3.4mm
      #8 = 4.0mm
      #10 = 4.7mm
      #12 = 5.6mm

  19. Use slotted screws all the time, but the slots must face the same way, either vertical or horizontally just so they look so much better.

  20. There are several advantages to Phillips screws. First,they are numbered, as are Torx and Robertsons (square drive). A number 2 screwdriver fits a number 2 screw. They are standardized as opposed to who knows what the depth or width of a slotted screw is. Second, Phillips screws are designed for production with pneumatic or powered drivers. They will “torque out” of the slot before twisting the head off. So don’t complain when your impact wrench jumps out and scars your piece. They were originally adopted by the automotive and aviation industries in the 1930s.
    Torx and Robertsons will twist the head off even by hand if they aren’t too big. Boat builders hate Robertsons and I presume Torx if they are used now. Think about trying to get the paint out of that tiny square hole to pull off a plank.
    Bottom line: “modern screws are extremely useful. BUT they are the UGLIEST thing on a piece of quality work.

    1. Johannes Linkels

      @Peter Oster: What is “torqueing out” of a Philips screw? My experience is that when trying to remove a Philips screw which is too tight, the cross slot simply becomes round. I mean even when using the right Philips bit or screw driver.

  21. Have you ever used “SPAX” screws (TORX or PZ head)? I am using it all the time without predrilling, because these screws have square part of the tip that works like square awl. The downside is that it does not have flat head. 🙁

  22. duncan robertson

    I’m an amateur antique furniture restorer and stick with traditional methods. I’ll never use any other screw other than a traditional slotted head screw. I recently had to remove the cappings from my conservatory roof where Pozidrive screws had simply been forced fitted with a screwdriver and covered with plastic wood; the worst joinery I’ve ever seen. Many heads were stripped so a screwdriver was useless. The metal used in the screws can’t be drilled for a reamer so getting them out was a nightmare; I hate them! I collect slotted head screws from wherever I get them and that includes ones I’ve removed from old furniture, some well over 100 plus years old and still going strong.

  23. Michael Briggs

    Great article Paul. Over the years I have been caught many times, taking short cuts when deep down I know I should have pre- drilled. Knowing the physics and behaviour of various wood types under pressure should trump lazy techniques any day.

  24. Thanks Paul, a long neglected area where screw technology has moved faster than practice. Ive found myself buying modern screws without much idea of how they differ, what they are actually designed to do and how best to use them. They come with little information but their cheapness and availability make it too easy. I spent hours trying to source those lovely black japanned screws and you have to search hard to get them. Pop into any hardware store and there are racks of these new type screws. Your thoughts have made me think.
    Some of us have fallen for the idea that these new screws are quicker, cheaper and somehow better than the more traditional screw types. Ok if you’re a chippy making carcassing then use the cheap quick method. But it doesn’t make sense to put all that work when doing bench work and then just get the power tool out and force in random bits of metal. And don’t get me on trying to find the right bit for the many different cross heads….
    Thanks again Paul.

  25. I always measure the major and minor diameter of threads – minor being the shank in the thread area. And, if my drill cases don’t have the decimal dia written by the drills, I add it. I do this for all my drills whether fractional, letter, or number size drills. I even have some metric drills but many of them are essentially the same dia as others. Maybe I read Paul’s article as – always drill the appropriate size hole in the area it is needed.

    Paul always makes us think and teaches us. This is the best one can do.

  26. Learnt from experience. Take the time to pre drill. I have also just recently bought a set of tapered drill bits for 4-12 screws, Makes life easy. AND when I use Brass, I always thread the hole with a steel screw first. A beef I have is the screws you get with the hinge sets seem to be too big a head and sit proud of the hinge plate, ( talking small boxes here), meaning the lids do not sit properly. I have found that I need to ‘Scotch’ the grooves, or have gone to a specialty hardware shop to get smaller screws.

    1. I have no idea what needing “to ‘Scotch’ the grooves” means here, Peter. Scotch? and what “grooves”?

  27. Thanks so much for posting these blog entries – I never cease to be amazed at just how agile your mind remains and the drive to continue asking questions and looking at every day items is indeed endless. I for one appreciate that and am so glad you blog about things the rest of us have so much less experience with, even if you have been driving screws for decades on end! Please keep up the good work as it proves that an enquiring mind can learn on a regular basis as long as it is willing to ask the questions.

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