(jazzy music) marc spagnuolo: i'm yourhost marc spagnuolo. today we're going to learnabout one the most important joints in woodworking,the mortise and tenon. the mortise and tenon jointis one of the strongest joints
delta woodworking tools canada, in woodworking and it's ajoint that you should probably master if you want to makehigh quality furniture. chairs, tables, doors, cabinets and tons of other pieces will allbenefit from the strength
of a mortise and tenon joint. if you ever plan on making something in the mission style,well you better get ready to become intimatelyfamiliar with this joint. check out this missionstyle entertainment center that i built a few years ago. if you can believe it,that's something that required 82 mortise and tenon joints. so what is a mortise and tenon joint?
well, for anyone who might now know, this is a mortise and this is a tenon. the tenon fits nice andsnug into the mortise creating a really tight and secure joint. now why is a mortise andtenon such a strong joint? well, the simple factthat we're inserting one part of a board into another board gives the joint a lot of strength. in addition, this jointcreates a significant amount
of long grain to long grainglue surface, which is really the best case scenariowhen using wood glue. now before going into detailon mortise and tenons, let's quickly take alook at some alternatives that you might be tempted to try. first, there's nothing. you can actually try to do asimple butt joint like this, but that's never a reallygood idea since the end grain sucks up the glue and leavesus with a glue starved joint.
that's not good for anybody. next you might consider using biscuits. this is a biscuit jointerand this is a little biscuit. now biscuits are certainly a step up from a simple butt joint. they're easy to make and they keep the boards aligned really nicely. but, they don't really bring a significant amount of strength into the mix.
these little guys justdon't penetrate deep enough. another option might be dowels. two dowels will providea pretty strong joint. in fact, strong enoughfor most applications. they're easy to set upand they don't require anything more than a drillbit and some patience. although there are numerousjigs on the market that will help you get consistentplacement of your dowels. another good optionwould be pocket screws.
any pocket screw fans out there? yeah, i thought so. now pocket screw technology's just a fancy way of saying "held together with screws". the screws are drivenat a very shallow angle and do a great job ofholding two pieces together. it's quick, it's easy, and if you don't mind screws it's a great option. but you'll have these screw holes
to contend with in the back. now they do make woodplugs for these holes, but if i have to gothrough that much trouble then i pretty muchnegated any time savings. now there is one lastalternative but i'm going to save that surprisefor a little bit later. i promise you though, it'sgoing to be "fescool". (banging drum cymbal) before we go any further, let's get
some terminology out of the way. now this area here that runs parallel with the face of the board,that's known as the cheek. the lip that surroundsthe actual tenon all the way around the board,that's known as the shoulder. so what do we start with first? the mortise or the tenon? personally i prefer tocut my mortises first. the primary reason forthis is that the mortise
is cut by somethingthat's a constant size. either a router bit or ahollow chisel mortising bit. and it can be tricky to make the necessary fine adjustments tomatch that up to a tenon. now the way a tenon ismade, on the other hand, allows for exact measurementsand slight adjustments. so it can really sneakup on the measurement by cutting a little bit ata time and test fitting. as a rule of thumb tenonsshould be made about
1/2 the thickness of the board. so in the case of a3/4 inch piece of wood, the tenon should be madeabout 3/8 of an inch thick. the rule of thumb fortenon length should be about four to five timesthe thickness of the tenon. again for a 3/4 inch thick work piece with a 3/8 inch tenon thelength would be between one and a half and oneand 7/8 inches long. this measurement also depends greatly on
piece that we're gluing our tenon into. (banging sound) there are a number ofways to make a mortise. this is pretty much theway it used to be done. you can even use a drillpress and a forstner bit to hog out most of the materialand chisel away the rest. well i could use my feetto go down the road like fred flinstone in my car ifi wanted to, but sometimes you just need to takeadvantage of technology.
i find that when it comes to making a mortise and tenon joint, power tools are the fastest and most accurate way to go. that doesn't mean you shouldn't learn to do this process with hand tools. in fact, practicing some of these classic techniques is a great way to improve your manual dexterity andconfidence with hand tools. most of you probably own arouter so this particular
method is like to be themost feasible option for you. now i prefer to use anup-spiral straight bit for creating my mortises. an up-spiral bit gives usmore efficient cut because it pushes the wood chipsup and out of the hole. the disadvantage is that the up-spiral bit may also tear out some of the wood fibers near the top of the mortise. but with a good, sharp bitthis usually isn't a problem.
and even if there is alittle bit of tear out, it'll most likely be coveredby the shoulder of the tenon. now you can use a down-spiralbit if you have one, but they're bettersuited for shallow holes. now i actually need toget a new up-spiral bit, so i'm going to use mystandard straight bit for now. alright, let's set up for our mortise cut. mark spagnuolo: i begin by attaching an edge guide to the router base.
using double-stick tape,i attach a second board to the mortise board and thisgives my rounter the extra support that it needs tostay balanced and safe. i then clamp the boards betweentwo dogs on my workbench. after marking the locationof the mortise using a pencil and a straightedge, i carefully set the straight bit right to the pencil line. after bringing the bit downto the surface of the wood i use the built-in depth gauge and stop
to set the plunge depth. with safety gear on and the dust extractor attached, it's time to start routing. (sawing sound) if the depth of the mortise isgreater than 3/4 of an inch, you may want to considermaking the cut in two passes. when you're done you should have a nice, smooth walled mortise. you'll notice that ididn't use stop blocks.
i simply routed it to my lines. this makes the set upgo a little bit faster and if i go over the lineby 30 second of an inch it really isn't going tomake much of a difference. the joint's going to be just as stable. one other thing to note isthe fact that the mortise now has round edges. it means we'll either have to round over the edges of our tenonlater or we can square
up the corners of the mortisewith a chisel right now. i prefer to round over the tenon. call me lazy. now i'd also like to mentionthat you can certainly use your router table to make a mortise. but that usually requires slowly dropping the work piece onto a moving router bit, which is not exactly myfavorite thing to do . so if you can avoid it, you'reprobably better off taking
the tool to the wood ratherthan the other way around. ever wonder if you coulddrill a square hole? well with this machine you can. this is a hollow chiselmortiser and you can find these for as littleas 200 dollars and probably even cheaper if you find a used one. it is a one-trick ponybut when that pony's trick is an essential woodworkingtask like making mortises, it's really a good investment.
now this machine uses aspecial boring bit that's housed inside of a four-sided chisel. now as the bit hogs outthe bulk of the material, the chisel slices the holeinto a nice even square. let's do a sample cut. mark spagnuolo: settingup the mortiser is easy. with a pair of gloves on iinsert the bit and the chisel keeping the chisel aboutan 1/8 inch from the top. i then tighten the chiseland the bit into place.
once the bit is secure iraise the chisel to the top. this technique resultsin the bit protruding just ahead of the chisel which results in a much more efficient cut. placing a piece of scrapagainst the fence, i rotate the chisel so that it's squarewith the fence and the open end of the chisel faces eitherto the left or to the right. this allows the woodchips to exit the hole reducing friction and reducing heat.
using a mortiser is a lotlike using a drill press, but requires a lot more pressure. in fact, most people are quitesurprised by just how much force it takes to plungethe chisel through the wood. if you've noticed by bulging biceps in previous episodes, now you know why. seriously though, i actuallybroke the ball joint on my mortiser once simply because i put way too much pressure on it.
the culprit was a dull chisel. word to the wise, keepyour chisel sharp using a cone-shaped diamond stone. today i'm using alderso it cuts like butter. (drilling sound) (banging wood) mark spagnuolo: nowlet's talk about tenons. of course, just like withthe mortise, you could use a saw, some chisels,and do this by hand.
but for all the same reasonsi prefer power tool methods. my favorite methods all involvethe use of the table saw. many of these cuts could be accomplished on the band saw, as well,but i find that the table saw produces a smoother, more accurate cut. mark spagnuolo: thefastest way that i know to make a tenon is to use a dado blade. this is a special stackof blades that allow you to adjust to any size you need
using these chippersand some magnetic shins. just make sure the arbor of your table saw is long enough toaccommodate the extra blades. mark spagnuolo: switchingto a dado blade is simple. i remove the "zero clearance" insert and remove the splitter. next i loosen the arbor nut using a piece of scrap to immobilize the blade. i assemble the dado blade with several
chippers between the outer blades. the final width is about one inch. when tightening the arbornut i find that most people tighten way too much. i usually secure the blade with my fingers with a wrench on the nut and give the wrench a few taps witha piece of scrap wood. as soon as the blade feels like it's going to slip out of yourhand, it's tight enough.
mark spagnuolo: now that we've got our dado blade installed notice that i have to remove the splitter in this case. number one because theinsert that i use with my dado blade doesn't havea space for my splitter. secondly and moreimportantly we need to pass this over the blade withoutmaking a through-cut which would actually cause a major problem if we hit the splitter.
after i mark the cut lines for my tenon, i like to set the fence up as a stop. now this will allow me tobatch out as many tenons as i need and they'llall be exactly the same. now, there's a potentialsafety issue here, though. if i use the fence as a stopwe could have a kickback when the work piece is over the blade and wedged between theblade and the fence. that's when i use my littlehandy auxiliary stop.
it's shop made of three pieces of plywood and a couple of bolts. now as long as the stop isin position before the blade, the work piece will beproperly indexed for each cut without the danger of being wedged between the blade and the fence. mark spagnuolo: usingmy adjustable square, i mark the location ofthe tenon's shoulder. i don't adjust the blade to thefinal height on the first shot.
i like to do a few test cutson the tip of the tenon. this way if i go too fari still have the rest of the tenon to correct the error. after a quick test fitwe can see that we need to remove quite a bit more of material. test fit numbers two shows that the tenon's just a bit too big. i raise the blade just a little bit and take another cut on both sides.
um, yeah, who's the man? with the fence adjusted and the blade set at the perfect height it'stime to cut the entire tenon. i usually cut the tenon inabout four to five passes and then flip it overand do the other side. using the same methods as before, cut the sides of the tenon, if necessary. and that, my friends, isa tight fitting tenon. if the tenon fits too tight, a light touch
with sandpaper usually does the trick. although it doesn't do me any good now, a piece of scrap wood double-sticked taped to the miter fence willhelp prevent tear out. mark spagnuolo: now you could do this same operation with your standard blade. you just nibble away thematerial a little bit at a time. this is ok if you haveone or two tenons to make, but if you got a wholebunch it's a tedious process
and the resulting cut's usuallya little bit less than ideal. mark spagnuolo: now thenext method requires the use of a special jig known as a tenoning jig. you can pick up one ofthese for about 60 bucks. the basic idea here isto hold the work piece in a perfectly verticalposition while passing it safely over the blade. the resulting cut isextremely smooth and accurate. and with the micro adjustments here,
you can easily dial in the perfect cut. time for an equipment check. tenoning jig, check. eye protection, check. piece of wood, check. spongebob pencil, check. that's how i roll. mark spagnuolo: after marking the location of the tenon shoulder, aswell as the tenon's profile
on the end grain, i adjustthe fence to my pencil line. i then adjust the blade height just a hair under my other pencil line. i then cut a single curve onboth face sides of the board. i adjust the blade height one more time to cut the sides of the tenon. this time i'll take repeated passes until all of the material is removed. it's just easier to finalizethis dimension right now.
before using the tenoningjig, i always make sure that the side and back stops are square. using my curve cuts as a guide, i adjust the blade height inpreparation for the jig. while holding the work piece tight against the back and side surfaces i use the built-in clamp tosecure the work piece. i then use the jig'smicro adjustment feature to make sure that the blade is about
a sixteenth of an inchaway from my pencil line. with the work piece securewe can make our cuts. be sure to wave at thecut-off piece as it flies harmlessly past your right hip. after several rounds ofcutting and test fitting we now have the perfect tenon. mark spagnuolo: now itmay seem like i'm adding steps by not aiming for mypencil line on the first shot, but believe me, you're workwill be far more accurate
if you use this relativedimensioning method. in fact, i use relativedimensioning on every project and for every type of joinery that i do. i'll go into more detailon relative dimensioning in a future episode. everything we've doneso far is a variation of what's known as an integral tenon. where the tenon is actuallypart of the work piece. an alternative to this methodis known as a loose tenon.
it's a joinery methodwhere you create a mortise in both work pieces andjoin them together with a separate piece of woodthat serves as our tenon. it's kind of like a really strong biscuit. it's a perfectly viable optionand it actually can be just as strong as a standardmortise and tenon joint. one big advantage here isthe fact that the tenon stock is going to be milled fromone long piece of material. so it'll all be exactlythe same and you can
make a bunch of tenons in one shot. and if you use a routerbit that's perfectly sized for a piece of plywoodyou can cut all your tenon stock from sheets of ply. can't get any easier than that? one big disadvantageis that it's difficult to create mortises in the ends of very long pieces, like table aprons. i'm ready!
now keep in mind that ifyour mortise has rounded ends like it will if you usethe router, you might need to round over thecorners of your tenon. you can do this with a chisel, a rasp, or even a sharp utility blade. now sometimes you put thetenon into the mortise and you see that there'sactually a little bit of a gap. you can't really get it to seat properly. so either your tenon's too long, which is
an easy fix, you just trim it down. or you might need to relievesome of the material here on the shoulder betweenthe edge of the shoulder and where the shoulder meets the tenon. what you really want todo is just with the chisel create a little bit ofa concave shape there so that really the onlything touching the next work piece where themortise is this outside rim. it's not going to affectthe strength of the joint
because all the strength isin the long grain glue joint. so just make that concave and that should give you a perfect fit.