Tolerances In Wood

I’m working, planing and thinking or is it the other way around? Attention in two tasks is always an alternating process and never truly bipartisan in that usually the ability to concentrate on two or more high-demand tasks soon obviates deferment one to other in measured exchanges according to priority. I switch between three planes and my thoughts are on the beech wood I am planing. I noticed that where the wood had been exposed to the atmosphere surrounding it for the last few years the surface was harder to plane because the wood had greater resilience. Ripping the 5 1/2″ wide 1 1/4″ thick section into two 9/16″ thick pieces and planing these inner faces I found less resistance as I worked. This ‘inner’ work is telling. And it’s because of this and these types of encounters that I say hand-tool woodworking is nothing like the same engagement with the material as machining wood.

So why does this matter? Different strokes for different folks, eh?

Well, I learned something in making this project that I would and could never have learned by passing it into or over the revolving cutterhead of a power planer. You see, it’s a much deeper level of knowledge and by this, I understand the ‘this one‘ wood might be used over another or that this work will take longer than using some other wood.

A questioner asked me why I switch between using a knife for some delineations and then a pencil for others. Well, it’s usually, mostly, because of this insider knowledge I’ve gradually and slowly accumulated over my six decades in the saddle and never by something read because the something read is unwritten and then too often unspoken too. That’s why I am writing it here and am willing to explain it more fully whenever we video my projects. This is what is different about my platforms and channels. I have a lot to compare things with over those sixty years of daily making. The spalted beech is radically different in the working of it to the newly cut five-year-old stuff kiln dried and prestressed by the process. The air-dried spalted material is much more stable as is all wood that is air-dried but no one will tell you that anymore. Especially those who sell wood bought and sold commercially.

Knowing how density in wood affects the tools and the joinery can only be had in the doing of woodworking and by that, I mean only (with emphasis) by using hand tool methods. By this, alone wood always gives feedback in different measure and in different ways according to our sensitivity, constantly. As soon as the plane surfaces the board we have a mass of information to work with about that very specific wood, that particular area on the side of the workpiece and in that section that will be different than the wood a foot away. The more handwork you give to your woodworking the more conversant you become and the greater your knowledge the greater your success will be. It’s this intimacy that sets us apart as makers. Whereas machinists often, often, and for no good reason, get offended by my advocacy for handwork, I hold to my belief that this level of working wood seems to draw a different and more full picture and understanding of our work, our wood that just deepens our knowledge. Ideally, everyone should try both ways of working wood, the hand methods and the machine methods. The problem is that using any of the woodworking machines takes only a few minutes to expedite the cuts but using hand tools with a good level of proficiency might take many many hours, days, weeks and more to gain the kind of working knowledge I speak of. Our kind of learning through the senses is a never-ending experience that gives us the depth of knowledge as well as a sense of anticipation telling us that there really is too much to learn beyond the mere machining wood but it cannot happen any other way.

The knife versus the pencil can really only be understood by direct comparison and in no way just once but by many repeats in many wood types and as often as you have time for. Every stick and stem of wood reacts differently to hand tools and you get to a point where you can indeed look at a piece of wood and pretty well know what reaction you will get. Of course, too, every stroke you make with the saw, plane or knife and chisel is dulling the cutting edge you are working with. This makes every cut different at the most micro of indiscernible levels but taking the difference from the beginning first cut and comparing it to a hundred cuts later also gives better understanding of how things shift.

Working in the beech this past few weeks, planing the surfaces, inner wood and outer wood, sawing with and across the grain with various saws ranging from modelling saw to rip-cut handsaw and all in between gave me a wide range of different feelings and these were not at all experimental but real work. The number of knifewalls came to over a hundred and then the chop cuts from the chisels used came in the hundreds too. I gained tremendous insight to beech but that was because I was interested but not just interested. No, more than that. I was being governed by my obvious feelings, the sharpness of my tools, the distance in cuts from my delineation lines in pencil and by knife.

Using the pencil proved more accurate and tolerant than the knife and it is this I want to talk about. Knifewalls around dovetails is establishing the highest extreme of intolerance. Cut to the knifewalls and the dovetail will not go together without serious hammer blows and the wood is more likely to give somewhere. Some will disagree with this but no matter. Experience tells me that knifewall tracing to accommodate a counterpart results in ultra-high levels of friction with glue added at the level ensuring that the joint will never go together as is. What we really need is not a knife-splitting hair but a judgement following clear pencil lines. If I ever had to choose between only using a pencil line or a knife line I would most likely choose the HB (#2 USA) pencil. I sharpen this repeatedly as needed until the layout is done. The pencil is more versatile, often clearer and super-sharpenable. So what more is there about the pencil?

Some woods are spongily compressible. I can name a dozen of commonly used ones right off. For some wood types, it’s to do with fibre softness and the best way to consider this would be to start thinking differently in the same way we might consider other materials if indeed you understand other materials. Stack up a ream of photocopy paper to 5cm deep and clamp the stack in the vise and it will perhaps then measure only 1mm less at 49mm. Do the same with corrugated cardboard and it will go down to 6mm. Both are paper products made from tree pulp fibres. materials of different types have some measure of compressibility. Did you know that glass is considered a liquid but that’s not the case at all. Glass is an amorphous solid existing somewhere between between the two states of liquid and sold. Consider it more a highly resilient elastic solid, meaning it is completely stable. I consider wood to be more like straws with capillaries and then strands of wool both of which make it compressible in different measure. No two woods are the same but can often be comparable even though the variance is massive even within each species. The growth of wood varies according to the weather conditions and the environments in which that wood grows. This is as unpredictable as the weather itself is today. The output of growth creates a natural unpredictability. This in turn presents those who work their wood with hand tools the one thing that is absolutely predictable. Wood is mostly unpredictable. Once you accept this, the more successful you will become.

Fitting dovetails into their respective recesses causes an interlocking of surface fibres if the meeting faces come from the saw and not the chisel. I believe that these fibrous surfaces give the best adhesion inside the joints we create. When the wood is pare-cut with a chisel, as some advocate, we lose this ‘toothing‘. Some woods, beech as a good instance, have less absorbency and benefit from the toothing a sawn surface provides. These facts, and they are facts, are not written but they should be passed on hence my labouring these points here and now so that perhaps the 50,000 woodworkers who will read this will keep it, use it and also explain it to others and pass it on in the years to come. DovetailS in a slightly tighter counterpart enter a gradual compression in themselves and then also the pins on either side which in turn creates its inevitable domino effect into the adjacent dovetails and pins. One oversight one in the middle or elsewhere will increase pressure on the others. This knock-on effect can advantage us and disadvantage us. We need to know what these tensions and pressures are in our working no matter how long in the tooth we are and no matter how long we know this wood type or that one.

Understanding the toothing of meeting surfaces to joints, of course, means that we need to saw accurately in our cutting tight up to lines and keeping to any angles used in the joinery so that those surfaces do indeed compress evenly and the fibrous surfaces mate well. This strikes apprehension in this new to working wood because they find this requirement more challenging but are quite confident about creeping up on the final levels. Indeed, some advocates eschew off-the-saw advocacy but not for any of the valid reason I give here because, well, they just never thought of it. Of course, 99% of the woods we access will saw and give excellent toothing so why not just go ahead and use whichever we prefer between the pencil and the knife? As I said, the knife is intolerant. We tend to cut right up to this knifewall but then find the recesses are actually too tight for some really dense-grained hardwoods like ebony, rosewood and several others. These woods are not comprising, not absorbing, inflexible and stubbornly resilient. These are the hard woods to work with to get gap-free joinery with. The knife tracing around the dovetail to establish pin positioning results in absolute cut lines. The problem most often is the tightness of the joinery and especially is this so when you have many dovetails to form a corner. The pencil lines seem more tolerant, more absorbing, more flexible and so on. That does not mean we should never use one and not the other but that we make our decisions based on out intimate knowledge.


  1. “[P]erhaps the 50,000 woodworkers who will read this will keep it, use it and also explain it to others and pass it on in the years to come.”

    Manywill, Paul, but even more if these superb essays someday appear in a companion book to go with Essential Woodworking Hand Tools, my daily reference companion.

  2. Having decade of experience with power tools and only sporadic opportunities for hand tool use while building custom homes, I agree, mostly, with your statement of wood characteristics being readily noted in hand tool use and not at all in machining wood. One notices a great deal of difference in woods when the majority of work is power tools. I suspect the hand tool only crowd would miss those subtle changes in resistance, in tone of the cut. They are there, nonetheless. It gives a foreshadowing of what the hand tool experience will be. No, not precisely, but one does notice. To say there is no ability to discern wood characteristics with power tools is like saying Stanley planes are all you need. Neither is correct.

    1. To say there is no ability to discern wood characteristics with power tools is like saying Stanley planes are all you need.” Not even similar, Murphy. Hope that is your first name. Not wanting to be rude or curt.With power equipment the feedback is so minimal it is barely discernible if at all discernible in any way other than perhaps the power-feed might need a nudge by hand or the sound of motor strain might possibly send a message.

  3. “Knifewalls around dovetails is establishing the highest extreme of intolerance. Cut to the knifewalls and the dovetail will not go together without serious hammer blows and the wood is more likely to give somewhere.” Thank you Paul! I have been living this issue for quite a few years and couldn’t figure out what I was doing wrong. I will try using pencils a bit more to see how it goes. I am just about to glue up the carcass to Christian Becksford’s 15 drawer shaker chest (30 linear feet of hand chiseled cut housing dados – took a while but so satisfying). With 15 drawers, there will be a lot of dovetails to cut. I have some nice curly cherry for the fronts and will use poplar for the sides. Most importantly, I will use a sharp pencil to transfer the joinery lines.

  4. Here we go again with the power tool advocates vs hand tool only.
    We are not talking the same language!

    There are things you notice with power tools like how some woods can quickly burn if your feed rate is too slow or how much silica is in the wood by the sparks you see. By the noise and sound when cutting on a shaper you can tell if your cutting against the grain or how a table saw sounds when cutting against a hard knot or wood moving because of stresses in the board your cutting often binding a blade as you make your cut. You can tell when your cutters are dull by the sound they make, anyone who has heard a dull portable saw cut when builders trim 2x4s will certainly say there is definitely feed back.
    I found that the problem with machines is by the time you get the feedback when making fine furniture is it’s too late and you have ruined your piece. Building a house is not fine woodworking it’s carpentry, it doesn’t mean it’s not quality work but it’s different kind of work. Most certainly not requiring tolerances in thousands of an inch.

    1. “I found that the problem with machines is by the time you get the feedback when making fine furniture is it’s too late and you have ruined your piece.”

      This should be your main point, Tom. This is my experience too – once the machine has given the feedback that something has gone south, I usually need to grab a new piece of wood. That usually does not happen much with hand tools, although I cannot say never will.

      To me, one huge difference in this feedback we are talking about, is that I get feedback both from the tool I hold AND the piece of wood. If I use my router or my band saw, I see the RESULTS of that “feedback”. I can listen to the sound of the band saw to know roughly what is going on, but to get down to the root cause I need to bring out the “5 why” method…

      1. You might qualify “my router’ as I cannot imagine getting much feedback from a power router save to say that the scream of shattering wood and the smell of burning timber tell their own story. I have learned to discriminate between the two known routers with power router or hand router plane for crystal clear clarity.

        1. Good point! And I of course was talking about my power router – or «the squeeler» as I prefer to call it. My toothpick maker 2000! The feedback I get from that one is virtually nil, sans the odd jerk when difficult grain is encountered or the noise it makes when the bit starts chattering due to excessive feed rate (speed or amount of material).

          I always write «router plane» when I am talking about that particular tool. If not, I’ve also found that people mistake «router» for the plugged in type. 🙂 I know I’ve gotten two or three to look into this essential tool.

  5. I was exposed exactly to the same difficulty you mention in a project when I had to cut 80 dovetails to make 20 picture frames that I designed with a dovetail at each corner.
    At the beginning I was trying to cut the pins right along my knifewall. As I gained in confidence and precision I was finding myself able to cut very precisely along the knifewall but still I would have to pare cut a little to force the dovetail in and one or two times the wood did split.
    I finally found a kind of trick that work well for me, that is to mark along the dovetails still with the knife, but postionning the tails leaving a small gap (less than a millimeter) between the to pieces of wood. Without a drawing this is hard to explain, but that way, if the dovetail angle is 1/7 this gives around 1/7 of a millimeter of tolerance on each side of the tail and I found that the joint fits snuggly with no hammer blow and no splitting, and no pare cutting.

    Recently I reused the technique making some drawers and it worked well also. I am happy I had to make that much dovetails in that previous project, so I finally learned this. It indeed feels very good to be able to cut dovetails with the saw alone, and I also read your post about the rough sawn surface expanding and gripping a bit more under the glue, which gives a stronger and gapless joint. But to reach that I needed quite some practice and I would not have been able to do that as a complete beginner.

    1. Thank you for that description. After a long departure into the vortex side of woodworking, I am trying to come back to flat work and learning dovetailing is among my goals. Once I have my new shop set up and finish a Moxon vice, I will try your approach with a knife and the traditional approach (but with a pencil) and see what works best for me.
      Much obliged to both you and Paul.

  6. One fine point re knife vs pencil: I always a knife wall on both sides of a crosscut. This eliminates tear out and glue cross linking is not an issue on end grain.

  7. If you can read the way the grain is running there is no reason for not using a power planner to surface your product after you glue up multiple boards. As far as dovetails yes you can do this by hand but a dovetail jig and a router would probably work fine unless you’re into something like this. As far as ripping solid wood you should always over size your cuts to reduce the tension and then use a jointer to get a good straight edge size again glue up . I have been working with wood for about 40 years and have been amazed by how easy it can be if you’re willing to spend the time.

    1. I think this is highly simplistic really and it often comes from those who are defensive of how they work. My efforts are not really intended for you and nor are they to produce an argumentative platform. Of course, you cannot pass all boards of all types of wood through any planer and guarantee that the grain is always in your favour. That’s not likely to happen on the incredible grain you chose the boards for especially. I recall a stunning board of figured maple that came out smashed to smithereens on the outfeed platten. Machines have their place, of course they do and should. Also working wood for 40 years does not tell anyone anything. 40 years two hours a weekend or full time six days a week is a different story. Machining wood is indeed easy; it cannot get any easier in fact, nothing to it. But that’s not what we chose. Being that it’s the easiest of all and it is not anything like working wood with hand tools, there is no reason to draw a comparison nor to defend one over the other if indeed they are two very different animals as in one is woodworking and the other is machining so we should park that there.

    2. “If you can read the way the grain is running there is no reason for not using a power planner to surface your product after you glue up multiple boards.”

      You’re wrong, there are many reasons. I have many reasons for not using a power planer. I find it dull, unchallenging, noisy, expensive, energy inefficient (I don’t need the power of two horses to plane wood), unskillful. But then I’m not surfacing a “product”, I’m making a piece of furniture for friends or family. I think I’m probably the audience that Paul is aiming his blog and videos at, rather than you, Ron.
      Please don’t take this as criticism of your choice to use a power planer, it isn’t. That’s your choice, and I’m sure your products are both functional and beautiful as a result. I’m sure that there are many valid reasons that you have for choosing to use a power planer too.
      All the best,

  8. Dear me. Sellers,

    Thus might not be the right topic to replay.
    Lateley I was watching an episode of Wheeler Dealers on the Discovery Chanel where they visited the Morgan factory. In one shot my eye was cought by the wooden frames on which the cars were standing. They looked exactly like the saw horses you made. I made these saw horse a few years ago and they hold on very well, they come in handy in a lot of situations, not only for sawing wood.
    It’s funny how often I see or read something that reminds me of something you said or made. Everytime when I’m working wood at some point I hear your voice somewhere in the back of mind. Thank you for all the good stories, instructions and video’s, they are really usefull.

    Best wishes,

  9. The main reason why I use hand tools is that I prefer the silence.
    There a some cuts for me that would be simpler with a bandsaw, but I need the exercise and enjoy the experience.
    Otherwise, it would feel like working in a factory wearing ear defeders and driving to IKEA to buy furniture.

    1. Well, when I started out in the USA at the start of my migrating there every woodworker I met though my reasoning was nuts. All everyone saw, and I mean everyone, was that machining was the only progressive way. Noise was eliminated by a Walkman with earpieces in and everything else around you could scream all it wants. That’s not the case for every woodworker today. It’s been hard work preaching an alternative reality but there are lost of us now––millions in fact.

      1. I think this is why so many people of today cannot fathom how the pyramids were built and how the ancient laborers could form granite and other stones with such prescision. The notion that despite all the technology today, we cannot repeat it.

        And here I am, silly thing, with my mallet, rock chisel, feathers and wedges. Good thing Indid not know that the task was impossible before I started breaking rock face and forming stones in our garden!
        But I know the secret: resiliance and TIME!

        1. Interesting Vidar. I too have those stone working tools, but I struggle with anything other than basic splitting and shaping. I was doing some tiling work for a hearth a couple of days ago, and I needed to shape the porcelain tiles to the stone at the back. I couldn’t think of a way to do this with hand tools (the woodworking equivalent would be using a coping saw), so I used an angle grinder. It was messy, noisy work, but free hand cutting so it was still a challenge. Do you know if there is a way I could have done this with hand tools? Or is shaping porcelain tiles akin to working in MDF or other sheet goods?


          PS. apologies for clogging up your blog with an off topic Paul!

          1. I would think you score the tile with a diamond wheel then break off the excess with pliers (there are special ones for just that application). Similar method to glass. For fine details, a coping saw with a special blade can be used – or you can use an angle grinder with a diamond blade. Nothing wrong with that, but it is a messy business! I believe sand paper works great as well – the “poor man’s rasp” comes to mind!

            The same principle can be used for stone work – chisel a line where you want the stone to break and continue working along that line until something happens. Think of it as your knife wall, but you obviously do not remove a small wedge. 🙂 Of course, the success of this method depends on the “grain” (so to speak) of the stone. There could be micro cracks or built-in stresses that causes trouble. I’ve had good luck with uniform granite, though. The stone equivalent of quarter-sawn, straight grained oak. 🙂

            This is off topic, but it is indeed amazing how HAND TOOL WORK is so similar across different applications! 🙂

            But let us end this here – back to woodworking! 🙂

          2. Yes, thanks Rico. I always enjoy seeing your well thought through contribution. I’d rather stay with woodworking really. That’s why I sometimes, more often now than before, I take them down after a day or less. And I also take down any distractions too these days.

  10. Hello, paul. I have a question that I have been trying to ask you for years now, when do you stop when preparing a piece of wood, in other words at what point do you feel that the piece of wood is ready for the next step. Let’s say there is a corner on the plane that is like 0.2mm less than the other three corners, (wood size is about 200mm*600mm*25mm)do you go for the other three corners?

    You have certainly encountered this problem with your students in your teaching and how do you instruct them? I would like to hear your detailed instructions

    1. 0.2mm isn’t very much, I doubt it would make a huge difference. Certainly something that could be worked around. A couple of passes with a smoother across the rest of the board would deal with it if it bothered you. It would also depend on where the wood was going (even if it was greater than 0.2mm). There are so many individual pieces in an item of furniture that don’t need to be perfectly dimensioned (the outer faces on a table leg, aprons, bottom of the tabletop, back of a drawer etc. that you’d base your decision on those aspects. Also, you mention that its 0.2mm less than the others, which suggests that the board isn’t twisted, simply less in thickness. Twist would be more of an issue than material thickness in my opinion.

  11. Vidar, in answer to your question about tiling, You can buy round diamond grit coping saw blades exactly for this purpose. It is simple to use as it saws in any direction. Slow, though, but that is good as far as I am concerned. Quiet and minimal dust that falls below the saw rather than being flung into the air. Hmmm, just like hand woodworking.

Comments are closed.

Privacy Notice

You must enter certain information to submit the form on this page. We take the handling of personal information seriously and appreciate your trust in us. Our Privacy Policy sets out important information about us and how we use and protect your personal data and it also explains your legal rights in respect of it. Please click here to read it before you provide any information on this form.