How a little wedge makes the STRONGEST joint ever!

lately we've talked about the strength of glue joints and the efficacy of mechanical fasteners such as our video on nails and our video on pocket screws and all of these are perfectly acceptable forms of joinery if you use them in the right places but not all woodworking is about gluing or screwing parts together sometimes you want to fit your parts together with mechanical joinery for those projects that require the highest level of strength and perhaps the strongest joint in all of furniture making is the wedged mortise and tenon though i suppose you could make a case for the draw board and pinned mortise antenna but we already made that video the wedged mortise and tenon is different from a standard mortise and tenon a standard mortise features straight sides that fit a straight tenon this joint provides tremendous resistance to shearing forces and it also resists linear forces through racking or leverage this is possible by the mechanical nature of the joint lots of wood must break for a mortise and tenon to succumb to those forces perhaps the only weakness of a standard mortise and tenon if you may call it that is through tensile forces which may pull the tenon straight out of the mortise there is no mechanical component to a standard mortise and tenon that resists that type of force glue alone must hold the tenon inside the mortise glue is really strong but you can't beat the mechanical strength of solid wood a wedged mortise and tenon on the other hand solves that problem by adding mechanical resistance to those tensile forces the tenon is flared open on the exit side and the mortise is formed into that shape by the means of wedges that lock everything together if you want a joint that will never come apart the wedged mortise and tenon may be your best bet especially if your project calls for a relatively short tenon such as when working with three inch thick stock that provides little room for a very deep mortise plus i think the wedged mortise and tenon is a really nice looking joint especially if you mix contrasting colors of wood so in this video i'll show you how to create this joint including creating a forstner bit mortise and a table saw tenant and i'll point out one of the mistakes i see made in other videos and articles on this subject now it's best to start with the mortise but you do have to estimate how big the tenon will be its thickness is simple that's determined by the size of your forstner bit and it's nice if you have a chisel of the same size as well the long dimension which we'll call its width is up to you my stock is an inch and a half wide so i'll come in about 3 16 on each end giving me a tenon that's one and an eighth inch wide again these are just rough numbers to lay out the mortise the actual tenon will be custom fit to the mortise after it's finished let's say i want my mortise to be about an inch from the end of this work piece then i add an inch and an eighth for the tenon's width and i carry those lines across the face that's the width of the actual tenon but i have to account for the flared shape once i add the wedges that's why i'm adding an eighth of an inch to each end this is the face side of the board the side that the wedges will be driven into i only add this extra width on the face side the back side is laid out according to the actual tenon width without the wedges so i simply carry my original lines around to the opposite face to be clear the back side is marked with the actual tenon width the face side is marked with the tenon width plus an eighth of an inch on each end for the wedges this accounts for the length of the mortise what about its width since i'm using a forstner bit to bore out much of the waste i need only layout the center of the mortise at this time so i pick an edge to measure from and i use a marking gauge to scribe a line where the center of my mortise will be on the face side then i use that same gauge referencing off that same edge to scribe the same center line on the back side the beauty of doing this with a marking gauge is the curve it leaves gives me some place to drop the point of my forstner bit into when i bore out the waste if you don't have a marking gauge you should get one for this and all other types of joinery i'll link to a decent affordable version below this video you'll also want to buy good forstner bits i love fish bits and i've used them for years i'll link to them below this video as well you could use that gauge kerf to reference each of the holes you're going to be boring one at a time along the length of the mortise but a drill press fence will make the process much easier and more accurate after you align it to your first hole keep in mind if you use a fence you should keep the same marked edge against it no matter which side of the work piece you're boring into i can borrow the first hole right at my line this is a luxury i have because i have a good forstner bit that's not going to drift or tear the surface fibers but my drill press chuck does appear to have a little run out in it at this extreme magnification i bore just past halfway through the stock then i move to the other line at the opposite end of the mortise this leaves me a place in the center to put the bits point as i bore out the rest on the other side i do the same thing using the same inner lines i'm ignoring the expanded outer boundaries on this side of the work piece the goal is a straight mortise that goes all the way through of course it must be squared up with a chisel so i use my gauge to mark a line along one side of the row of holes flipping the work piece and referencing off that same edge to mark the same boundary on the opposite face as well then i adjust my gauge to reference on the other side of the row of holes marking that boundary on both sides of the work piece excuse my shaky hands here which make chisel work difficult i get comments about it in every video it's a genetic condition called essential tremors and it looks worse on camera than it actually is once your mortise is squared up you can congratulate yourself for completing a standard through mortise this is your first time you should be very proud but now we're going to modify it to accept the wedges by creating a slope on each end from the outer lines on the front face to the inner lines on the back face a bevel gauge will make this easier so set it to the angle in question i'm marking those angles on the edge for illustrative purposes so you can see the shape the inside of the mortise must take but don't worry getting here is going to be way easier than you think this is a piece of 2x2 construction lumber i'm marking that same angle on it running in both directions this will be the guide we need to reshape our mortise here i have a scrap of plywood to protect my bench and another scrap that matches my work piece to give me some stability as i place the guide on top i align the guide block with the edge of the mortise placing the outward sloping reference line on what will become the left boundary of my mortise then i clamp everything securely and we're ready to chisel the side of the chisel goes right against the guide block which ensures my cut is straight in the side to side direction the line on the block helps me hold the chisel at the right angle in the forward to back direction i'm only pairing off a bit at a time big cuts are more difficult to control if your chisel is sharp and you pay attention to your guideline it's surprisingly easy to create the proper slope inside the mortise when one side is done switch to the other it helps if your chisel is the same width as your mortise that's why we cut the mortises before we cut the tenons so we can size the mortise to the tools that we have on hand our forstner bit and our chisel the tenon itself can easily be sized to the mortise later your eye may tell you that the mortise slopes from the outer lines on the face side to the inner lines on the back side but a ruler will help you see if there's a hump in the middle if the ruler touches both lines on both faces at the same time your mortise is finished a tenon is now cut to fit in the opening on the back which is the smaller of the two openings i'm using a rip blade on my table saw which has flat ground teeth i set the fence to the thickness of the work piece that has the mortise in it then i begin nibbling away the tenon's thickness just a teeny bit at a time because very little material is being removed the blade exerts almost no force on the work piece and it's perfectly safe to pass it over the cutters forward back and side to side just be sure to use a miter gauge to keep it perpendicular to the fence we don't free hand on the table saw check the fit then adjust the blade and continue sneaking up on the perfect tenon thickness be patient you can always remove more but you can't put sawdust back on once the thickness is right meaning it fits firmly without pounding it in you can repeat the same process to cut the tenon to width again using the smaller entrance in the mortise as your guide this is a proper fit requiring some pressure to assemble but no pounding of course we're left with some extra room on each end of the tenon and that's roughly the size your wedges must be in fact the lines i earlier marked on the edge of my work piece show what the wedges should look like i say they should be roughly the size because i like to make mine a little bit thicker than the eighth of an inch of room that i left for each of them because i want to drive them in tightly and compress those wood fibers to close up any minor visible gaps that i might have on the visible side of the joint later so i cut some stock to not an eighth of an inch but almost to 3 16 of an inch thick of course i've ripped it to a half inch wide because that's the width of my mortise my tent is three quarters of an inch long so i connect the points on the edge with a pencil and i remove the waste so i have my wedge there are jigs and other ways to make wedges but i just cut mine by hand on the bandsaw i suppose if i had dozens of them to make i might use some kind of jig they're videos online that'll show you how to do it sometimes i like to test fit the wedges at this point this is of course not exactly where they will ultimately go as you'll see but this helps me to see if they're going to drive in tightly now here's where i think some folks go wrong i often see people drilling little holes down by the tenon's shoulders then they cut a kerf straight down to each of those holes the idea is the holes will keep the wedge from splitting the work piece if they're too tight first of all the wedges would have to be really tight to split this work piece because the shoulders of the tenon would resist all but the most excessive wedging action if you cut your wedges properly you aren't going to split past those shoulders also if you cut straight down the wedges have to bend all that meat over on each side of the tenon that might be easy up at the top but how does it bend all that wood at the base without these fibers tearing that might cause the work piece to split past the shoulders which is probably why folks found that they had to start drilling holes to counter a problem that was caused by that straight downward cut here's a better way i'm marking in about a sixteenth of an inch along the base of the tenon that's all i need for meat down there then i add that sixteenth to the thickness of my wedge giving me three sixteenths and that's how far in i come from the corners at the top of the tenon when i connect those lines i have slopes that match the angle of my wedges if i cut along these sloping lines i create narrower hinges at the bottom that will fold much easier under the force of the wedges this does not weaken the joint whatsoever because there's still a lot of meat a lot of fibers to break down there at the little hinging points and glue is going to turn all of this tenons and wedges into a solid piece of material i'm not saying the other way is wrong i used to do it that way i'm just saying this makes more sense to me and i've seen smarter people than i do this way as well it's time to put it together i apply glue to all the surfaces and i insert the wedges ideally the sloping side should be facing inward because our saw cuts sloped in the other direction but it's really not a huge deal i use a block of wood to pound them home so i don't mar the ends too much and unlike a traditional mortise and tenon joint you don't have to wait for the glue to dry you can just sand or plane it flush and immediately see how it's going to look you can't tell me that that is not a good looking joint the end grain pine contrasts with the long grain and the oak wedges add an additional element the colors will really stand out under finish imagine this is a table or a chair leg it is not coming apart i think you'll agree that the wedged mortise and tenon is almost as strong and good-looking as i am see you next time for the last several years i've been replacing my cheap drill and forstner bits with quality bits from fish tools they're a family run company that still forges their bits the old-fashioned way try replacing your most used bits with fish bits using the links in the notes below this video and you'll see why i love them so much

Channel: Stumpy Nubs

Views: 100,295

Rating: 4.9733462 out of 5

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: I0Z2PdMzzhk

Length: 13min 31sec (811 seconds)

Published: Fri Sep 17 2021