let’s talk about your hole

[estimated reading time 8 minutes]

actually, let’s talk about a very specific hole — the hallowed mortise. we can talk about tenons at some point but those are really easy. and i always thought digging holes in (or through) pieces of wood was something rather basic. but i have, after years of being a teacher, discovered this is probably more distant from the truth than i could possibly have imagined. coming from a traditional-woodworking background in the japanese practice, this was something that was driven home before i even picked up a sharp tool of my own. but if you’re coming from a self-taught or western background, i think something may have been missed. actually, five centuries of western woodworking have pretty-much done nothing but confuse the question of cutting a mortise with one of strengthening steel bars and applying more and more mechanical pressure. what’s odd is that they had the right idea far, far longer ago than that and what’s happened is the application of laziness and industrial-mechanization logic to something that needed neither and has suffered painfully from their addition.

what am i talking about with such flowery language? cutting a simple mortise, of course.

to cut a mortise, you need two things. a basic bench-chisel and a hammer or mallet. you can use a big slab of wood or whatever other heavy object you happen to have nearby if you don’t have a mallet. or you can make a mallet. cause it’s lots of fun and everyone needs one eventually (ok, everyone needs one right away if they’re working with handtools). so what you really need is one thing — a chisel. to that, you have to add a stick and a stick in its most refined form is a mallet. if you’re using a japanese chisel like i prefer to use for all my excursions to the land of chiseling happiness, you can use a metal hammer to beat it into submission (gently). if your chisel doesn’t have a metal ring on the end, i would caution against such treatment and advise you live in firmly in the land of wooden mallets. either way, a big stick will do just fine.

what type of chisel? i’ll be very clear on this. don’t get a mortise chisel. just don’t. it will teach you bad habits and techniques. if you have a mortise chisel, put it away. sell it. give it away. burn its handle or something. don’t let yourself use it ever again and make sure nobody else does, either. it’s trained generation after generation of sloppy woodworkers to indulge in the most fundamental cardinal sin when working with wood — using a tool as a lever.

let’s start at the beginning. there are six “simple machines” — lever, wheel/axle, pulley, angled-plane, screw, wedge. in woodworking, several of these are vaguely-relevant but most simply don’t apply. you might have a wheel/axle setup if you make hinges or to use a sharpening guide. and it’s exactly how your brace/bit works. a pulley applies if you’re using a springpole lathe. an inclined-plane comes into the equation if you have to load your workshop in the back of your pickup and you may, though i never do as i hate them, add screws to your work if you’re inclined to work that way. there’s absolutely no place in woodworking for a lever, though. stick a chisel in a hole and start prying back on the thing like you’re trying to break into a locked door? shame, shame, shame.

woodworking is the application of a wedge in various places. from the beginning of the trip from tree to furniture to the end, it’s all wedges. the tree sends wedge-shaped roots into the ground to search for water and nutrients. once it’s ready to be turned into lumber and fuel (mostly fuel, i suspect, given how much of the tree isn’t useful for boards), you take an axe to it. which is a wedge made of steel or iron. or you can use a chainsaw. which is a bunch of wedges in a row spinning around very fast. but we’re civilized handtool people, right? we use axes and handsaws (i use a battery-powered makita chainsaw if i have to take down a tree so i’m a forest-barbarian but i’m proud of it and at least i’m not encouraging more carbon into the atmosphere as i kill the majestic oak). anyway, once it’s down, you have two choices — split it with a froe, wedges and a heavy hammer or cut it with something like a bandsaw. again, a froe is a wedge. wedges are wedges (i’m starting to want potatoes) and the bandsaw is a series of wedges in a row that just happens to move ridiculously fast. when the wood is dry, we take to it with more saws and chisels and scrapers (wedges), planes (also wedges), shaves (guess what!) and drawknives (yes, girl, even more of the same). all our edge tools should probably have a w on them — they’re not just edges. they’re wedges.

and this is a good way to think about handtool woodworking. it’s simply the formal, ritual application of sharp wedges to unsuspecting organic material.

note, none of these things ressembles a crowbar. a chisel is a thin piece of steel. it’s meant to resist pressure in one direction and only one direction. if the blade is 20cm long, that’s the heavy dimension — it’s meant to resist pressure along its length, not front-to-back or side-to-side. if you want to get its effective strength to work for you, it can only move in one direction. hold the chisel so the flat side is either staring you in the face or looking straight away from you, directly up and down, place it on a board and hit the end with the mallet or hammer. then pull it straight back out.

but a mortise is a hole. that’s not paring, is it?

well, actually, it’s just paring at an angle. if nobody has ever explained the simple paring method for cutting a mortise, here’s how it works. there’s a little shortcut but we’ll get to that in a minute.

draw your mortise with a pencil. now take your chisel (it should be narrower than the smallest dimension of the mortise or you’re going to have some problems because … well, it’s just not going to fit) and your mallet and score a line about 1-2mm inside all the way around the mortise. you want this line to be at least one good vertical stroke deep the entire perimeter as an exterior boundary. don’t chop deeper than this guideline without deepening it first or you could split your board or go outside the lines on your mortise and ruin the piece.

with that outside line finished, take your chisel and put it vertically in the center of your mortise — the hope is that it pretty-much fills the entire space from one line to the other. now tip the hand 45-degrees off vertical and give the thing a couple of good hard taps to push it solidly into the wood. pull it straight back out. move in the direction the chisel was digging twice the depth of your cut, turn the bevel the opposite direction, lean it the opposite 45-degrees and tape it until the wood v in the middle pops out. take the chisel out of the hole, move it back a couple of millimeters and repeat the process from both sides. now you have a deeper v. you can do this until you get to the depth of your desired mortise and keep working in both directions until you get to the sides. when you are almost at the sides, start getting closer to vertical with each step closer to the side and you’ll end up with a mortise the size of your guidelines. with that done, split the lines. go around the outside and pare vertically to the original pencil lines you drew for the mortise. you’re done. if it’s a through-mortise, i’d cut from both sides to avoid tearout on the other face but you can go straight through if you prefer and don’t care about (or have to surface) the potential result on the opposing face.

note, at no point did you do anything with the chisel other than push the thing either in the direction from its handle to its bevel or pull it straight back. no pressing. no levering. no prying. no bending.

now here’s the other thing about this technique that you might not have noticed.

every time you hear someone talk about chisel-work, they start with something that goes a little like this. “get out your stones and sharpen that bitch within an inch of its miserable life.” while this is probably good guidance, you may remember i didn’t mention anything about sharpening the chisel at the beginning. and that was for good reason. want to pare something precise where you’ll see the surface? like a dovetail? or the edge detail on a component? you need your chisel to be truly, spectacularly sharp. well, at least as sharp as you get from an extra-fine diamond stone. and that’s as sharp as you ever need to get for anything, i promise. beyond that and you’re just wasting time. but this method i’ve just outlined, unless for some reason you’re actually going to show someone your mortise, doesn’t need any of that. why not? the shoulders and cheeks will be covered by the mating piece. most mortises are blind — they don’t go more than three-quarters of the way through the board so you don’t see them from the other side, either. what does it matter if it’s rough? tearout? no problem. inaccuracy? no problem. slight misalignment? who gives a shit? this is the ultimate joint for beginners and lazy professionals. it looks perfectly-accurate despite often being made so quickly and inaccurately a child could have done better with its teeth. and that’s ok. woodworking is, in many ways, the art of knowing when to aim for perfection and when to accept hidden things will stay forever hidden and aren’t worth the effort.

the effect of this is that this may be the only professional-looking joint you can cut with a rusty screwdriver vaguely shaped like a chisel — a chisel-shaped object as they have often been called — those $5 things you get at harbor freight or princess auto, for example. no, don’t buy one of those things. it won’t be useful for anything else and you need some serious chisels for your woodworking. my point is that if you’ve been having bad results cutting blind mortises and you think the problem is that your chisel isn’t sharp enough or good enough quality, you’re barking not just up the wrong tree — there’s no tree and you’ve wandered into the enchanted forest. the problem is the technique.

by the way, if you want to speed up the process, my usual trick is instead of cutting a v in the center and widening it, i cut a bunch of left-sides of vs across the entire length of the mortise, flip the chisel and pare across — this is how axe-work is usually done with relief strokes. the same function applies but instead of chopping the other side of the v once, each stroke chops another one and you can ride bevel-down across the whole mortise and only have to do this once per depth-level. this saves an incredible amount of time but i’d suggest the basic method first until you get the hang of it and can handle the chisel with only one hand. once you can do it with one hand and keep the other hand only on your mallet, try batch-cutting multiple vs at a single depth and you’ll speed up even more.

so that’s the story of your hole. now go cut a few mortises and see how easy it is without a mortise chisel. and without even having to sharpen. you’ll be blown away by how quickly you can do it — i bet you can chop a mortise this way faster than you can set up a hollow-chisel mortiser or even get a bit chucked up in your drill and knock out the waste. this isn’t the only way to cut a mortise. and many amazing woodworkers really do take the pry-and-pray approach. but i wouldn’t dream of it. and i don’t think you should, either. try this and see what you think. i suspect you’ll never look back. thanks for reading, enlightened arboreal mystics. i leaf you in peace.

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thank you for reading. your eyes have done me a great honor today.