A common mistake of connecting corner desks and counter tops

a couple years ago we built some walnut countertops and like many counters these required a corner joint in that case we opted for a large miter about a year later we built a corner desk and in that case we opted for a 90 degree butt joint why did we choose one over the other how did the potential for wood movement factor into these choices and how do we create these joints so they would be strong and seamless while still allowing for that potential wood movement today i'll answer all those questions so you may choose and successfully execute whichever version of the joint you decide is best for your project let's start with a few pros and cons of each version personal preference is of course a major factor both can be attractive joints but you may just like one more than the other in our case the desktop featured a square edge while the countertop featured a profiled edge and this was a factor too if you try to butt two profiled pieces together you'll have a gap at the inner corner of the profile this problem may be solved by routing the profile after you butt your slabs together which is what we did but since a round router bit cannot cut fully into a square corner you either have to settle for a radius in that edge profile or you'll have to hand carve the transition to a point another solution may have been to add separate moldings after the main slabs were joined coping the inside corners as you might baseboards or crown moldings but if you choose to connect two panels with a large miter you may route the profile first if you want and then you'll get a crisp corner just like a giant picture frame automatically this is one factor you may consider when choosing between a miter or a butt joint for a large desktop or countertop wood movement is also an important factor even after a finish is applied wood will always swell and contract with the humidity in the air boards do not grow longer with the grain they only grow wider across the grain on humid days the width of a large slab such as a countertop or a desktop may fluctuate by an eighth of an inch or more and this movement affects miter joints differently than it does butt joints a butt joint features conflicting grain direction with end grain butting up against long grain you cannot permanently tie these two slabs together because while this side will grow wider this side will not grow longer therefore the seam between them must be able to move or the end grain half of the joint will eventually crack a miter joint is different while the grain still runs in different directions only the ends of those fibers are connected theoretically both halves of an end grain to end grain joint should grow and shrink together but that's not what really happens as the two halves of the miter joint swell wider without also growing longer the outer corner will try to open up likewise as the two slabs shrink narrower without growing shorter the inner corner will try to open up this phenomenon is much more subtle than the drawings here illustrate you won't even notice it in a small picture frame for example but wide slabs contain many fibers and the effect is magnified if the project always remains in a climate controlled house only a very fine gap might open but that movement will eventually compromise any glue that you plan on using so you must find a better way to connect your two pieces together now before we discuss the joinery we should discuss cutting the joints this can be an intimidating process because the slabs are very likely large and unwieldy and the last thing you want are gaps in your joint we cut one with the track saw and the other with a circular saw and edge guide the track saw was a little bit easier especially for the angled cut but both did the job it's important to make the entire cut in a single fluid motion do not pause mid cut or you're likely to leave a blade mark at each pause that might appear as a gap in the finished joint if you aren't able to get a perfect tight seam with a circular saw then consider cleaning it up with a router and a straight edge just skimming the end grain with a straight bit this will clean up any blade marks and ensure a tight fitting joint one more thing to keep in mind is you should not assume you must cut a perfect 90 degree or 45 degree angle in the countertop project we made a template from the cabinets at the job site and used it to mark the inner and outer corner of the joint so we could achieve the proper angle on the desktop we placed the two halves on top of the frame and then scribed the end of the panel that was to be trimmed to the edge of the mating panel this prevents errors that may have been made in the frame or in the cabinet installation from compounding into the tops as well now let's talk joinery we already discussed the necessity of allowing for wood movement and how glue has no place in either of these joints what we need is something to pull the two halves together and something to keep them on the same plane so the joint remains not only tight but flat and even this is a good place for some type of loose tenon joinery biscuits will work just fine as long as you have a good cutter that creates a tight pocket for the biscuit to fit into if the biscuit will wobble within the pocket it will be useless for alignment purposes a loose tenon router jig will work as well we made a video some time back about loose tenon joinery which i'll link to below this is essentially the same type of joint created by the popular festool domino remember these loose tenons and biscuits are for alignment purposes they keep the seam even so the countertop or table remains flat but they must allow the two halves of the joint to move side by side so they may expand and contract independently of each other this is why biscuits or other loose tenons are preferable to something like dowels the slots may be cut slightly wider than the biscuits or the tenon inside them giving them room to move in that side to side direction but not up and down these are dry assembled without glue in fact no glue at all is used in either the miter joint or the butt joint instead they'll be held together with metal fasteners for the butt joint we chose pocket screws pockets are bored into the end grain side of the joint not into the long grain edge then the exit holes are counter bored larger than the screw's threads when the joint is screwed together the heads of the screws pull it tight closing the seam if over time the end grain half of the joint becomes wider or narrower the shaft of the screw will not restrict that movement because of that extra room in that portion of the hole this movement is still possible even though the head of the screw is driven down tightly to fully close the joint seam the miter joint might also have been joined with pocket screws but the bond wouldn't have been as strong because the screw threads cannot bite into the mating end grain of the miter joint as securely as they can the mating long grain portion of the butt joint i'm not saying you can't use pocket screws in a miter joint i'm just saying it won't be quite as secure and remember a really large miter joint like this is unique in that it will try to open as the wood moves so just to be sure in this case we use what are called draw bolt joint connectors they're sometimes also called dog bone connectors they require a special slot that is easily created with a forstner bit and a simple router jig i'll link below to both the bolts themselves and to another video that we made showing the installation process in a little more detail i like these connectors because they are very very strong this thick slab countertop will never come apart both joints in fact are very strong because we took the time to understand the unique nature of each type of joint and now that you have an understanding too you can be confident when you have a large corner to connect see you next time when i decided to get more serious about woodturning i spent a lot of time researching turning tools i kept coming back to carter and sons these are m42 high speed steel these stay sharp about five times as long as my regular high speed steel gouges carter and sun is a small family owned business with exceptional quality and service check them out for yourself at the link below the video wait don't go yet if you're new here please subscribe and remember to ring the bell i would really appreciate that give us a thumbs up or better yet leave us a comment i always read them and be sure to check out the latest issue of stumpy nubs woodworking journal it's always packed with tips tricks and tutorials designed to make you a better woodworker

Channel: Stumpy Nubs

Views: 466,859

Keywords: woodworking, stumpy nubs, tips, workbench, table saw, scroll saw, drill press, quick tip, band saw, bandsaw, lumber, hack, hand plane, sharpening, tormek, worksharp, diamond stone, water stone, wood turning, bowls, lathe

Id: 4-OGtAs12ZQ

Length: 8min 52sec (532 seconds)

Published: Thu Jul 29 2021

Reddit Comments

[u/_mach]

Zero mention of the Haas coefficients at ALL. Like, why even press "publish" at that point?

[u/4WVZ]

It's cool to see a video with some of the science behind desk corners explained