Hand Cut Mortise | Ten Tips for Better Mortises

hi i'm rob cos and welcome to my shop if your mortise and tenon joints aren't where you want them to be that is a tough joint i've got 10 tips that may help improve them and get them to where you want them to be i'm rob cosman and welcome to my shop we make it our job to help you take your woodworking to the next level if you're new to our channel be sure to subscribe turn on that notification bell and don't forget to turn on the notification on your mobile device so you'll know every time we release a new video good all right back to the bench if you're building a piece of furniture that doesn't have a whole lot of mortises to cut for instance something like this i've got three on the bottom three in the top and of course six on the other side that's not a whole lot however the amount of time that it would take to set up a jig or a machine to do these particularly out there in the middle you could do them by hand a lot faster and like planing wood it's very satisfying to chop mortises by hand when it's done properly with a properly sharpened chisel and a properly made chisel cutting those little sections and seeing them come out is actually quite fascinating so i have done a complete video on cutting mortise and tenon we'll leave a link to that below but what i want to walk you through is share with you some tips that they may just make the difference between this being something easy and achievable and it may also help you discover why you've not been able to get them satisfactory or at least as nice as you would want them to be so let's get into it all right so let's the first thing we should consider is the actual tool itself what i want in my mortise chisel is to have the sides square to the back which means the sides are going to be parallel why well when you chop that keeps this from twisting and i also often will lay a block and i'm going to actually show you that and you want that side to be square to the back in order for that to work or i often i'm working to a line and again you want that side to be square to the back critical there are those that say no you want them tapered so it's easier to extract from the mortise no i don't believe that at all and i'll show you why so i'm going to show you this is actually an ibc chisel relatively new we just started carrying them so if i put that to that square on there there is absolutely no light on that side referencing or square checking the side to the back same on that one here's a less expensive one and if i do the same thing i get a fair bit of light on the inside and typically these are always going to have parallel sides so in whatever direction it's off from one that's exactly the case here if it's off like this on this side it's going to be off like that on the opposite side i i wouldn't i wouldn't use that so you want square sides and you want them to be at least as thick as they are wide that gives you lots of reference here so as you're chopping that lessens the tendency of this chisel wanting to twist in the mortise and the more closely you can keep that that side parallel to your mortise walls the cleaner that inside wall is going to be the better your glue joints going to be so square square sides thick chisel key to having a really good mortise chisel so number two really probably should have been number one but i had to squeeze that other one in and that is sharp like anything any edge tool the sharper it is the easier it's going to work primarily because the sharper it is the less effort is required the less effort means the more control you have but think about this when you're chopping a mortise and you're cutting through those end grain walls particularly as you're finishing the outside edges you're wanting that chisel to bite into that end grain if it's not if it isn't nice and sharp with a good flat back it's going to want to slide off of that makes it very difficult for it to hold on that end grain and cut down there nice and straight the other nice thing about having a highly polished and flattened back that has got a nice beautiful sharp edge is that it will be very predictable you know exactly what it's going to do when you put it into the wood so i take mine polish them up to the same level that i'm going to polish the bevel i'm going to walk you through this real quick so on our chisels you can take the handle off remove the ferrule now the nice thing about that is it'll lay nice and flat on the stone there's nothing to interrupt back here so i would go through the process starting at 500 or a thousand whichever you choose and i would go through and i would remove all of the grinding scratches from the factory when i do this i'm always moving from side to side just so i even wear my stone i would check and when i can no longer see grinding scratches i would just move right up through the grits until i get to my final grit in this case sixteen thousand now once you've gone through all of that that's a one-time procedure you never touch the back of the chisel again with anything but your finishing stone in my case a fifteen thousand when it comes time to sharpening the bevel a little bit of lubricant on both my core stone over here i'm actually gonna put this back together it's nice to have a little more reference to hold on to snug that up set that down these are a 30 degree primary bevel you need that for the amount of beading that you're going to do on this chisel set that on the primary bevel raise up just a few degrees now on something like this which is fairly narrow i like to do just a little short forward and back strokes if you do circles you're going to have a tendency to skew it so find your primary come up a little bit higher maybe two or three degrees literally short strokes and you can just slide side to side so that you're covering more surface area and you're not wearing one part of the stone that's probably going to take about 10 seconds maybe less do that until you can detect a slight bur on the back side once you do you're going to move over here to your finishing stone do the same thing referencing on the primary elevate a little bit higher than you did over here which means if i went up three degrees there i'm going to go up maybe four or five degrees here so that i'm only touching the very leading edge on this 16 000 grit stone remember this cuts fast this cuts very slow i've already straightened the edge over here i'm going to refine it over here hold it there little short strokes shouldn't take any more than five to seven seconds flip it over like this again you don't need very big strokes you just want to remove any bur get rid of any moisture and now that's ready to cut i don't bother doing the edge the sides i don't want to change the dimension of that at all i leave them as it is but as you do prepare the back what you'll notice is it'll give you nice sharp edges here and these are going to do a lot of the cutting on the side that'll leave you a nice clean wall inside your mortise and the cleaner and smoother that is the better the glue joint is going to be okay now let's talk a little bit about the dimensions because sometimes people get this wrong and it doesn't serve them well the the rule if you want to call it that has always been that when cutting a mortise and tenon use the one-third one-third one-third so here are the two typical sizes of wood that most folks are going to end up using three-quarter stock an inch and a half so in three-quarter if you're making a frame whether it's like this or like that if you were to put cut a great big mortise meaning leaving less than an eighth of an inch on the outside now the first thought is well that's going to make the tenon really strong because if we go over to the other piece we're only going to cut a little bit off of here and a little bit off of here and instead of losing this strength it's a three-quarter inch piece we're going to reduce it down to maybe 5 8 so it's still going to be pretty bulky however if you were to go ahead and cut a 5 8 inch hole or a mortise in here look at the little bit of material you have left on either outside edge well this may be good and strong but it won't take much to break that off so what we do instead is we come in here and we divide this up if it's three quarters of an inch this is a little bit strong we're gonna go a third which would be a quarter a third and a third so now there's our the outline of our mortise and then over here on our tenon we're going to do the same thing we'd actually use a mortise chisel to do this but i'm just going to pencil it in for you for demonstration purposes and you'd always end up having a little bit of a shoulder on both edges so that you can cover your joint and make it look nice and neat just finish that now well that has substantially weakened this piece because it's been reduced only a quarter of an inch it's balanced over in this piece so now when you put that together you're getting the most you can get out of the both of them and the compromise is going to make it so that you don't have any one piece severely weaker than the other of course and if i was going to be cutting this i would choose the size of chisel that corresponds with the size of the mortise i want so i would use a quarter inch chisel and everything would be referenced off of that i would chop my mortise and i would reference my gauge off of this same chisel and i would cut my tenon and then the two pieces would actually fit and of course on a piece of inch and a half stock we would divide that up into thirds in this case you're going to have a half inch half inch and a half inch on the other side so there's your there's the wall of one mortise there's the wall the other close that off on either end then you come in and you do the same thing with your tenon now you're severely weakening this piece by going from a full inch and a half down to just a half an inch but like i said that's the compromise that you have to make of course you always have a little bit of a covering with the shoulder out here and that would be referenced off of your half inch mortise chisel you would use that to chop your mortise you would reference with your gauge off of this chisel mark it over here and if you do everything right this will fit when you're done so follow that third third and third now the exception to that would be something like this where you're perhaps you're making a a bed frame and here's a rail coming into a big post where this piece is a lot bigger than this one in this case then i want to keep this piece as strong as possible and what i would do is i would go in and i would just have enough of a shoulder to cover the joint to make it nice and neat but i want to take the absolute least amount i can get away with preserving as much of this as possible and here it's not going to matter i've got so much material i would go in and i would match that up cut my mortise in here and now i've got a good strong joint in that application third third and a third unless of course you're dealing with something as i just example i just showed you there okay now i'll talk a little bit about laying out the mortise because i don't do it the way that others might first of all here's a mortise gauge this is the one that we make and i like this because it allows me to squeeze the mortise chisel between two cutters set that in there like that squeeze it and then this knob locks it in place and i use this for laying out the tenon however while it would you would only be natural that you would then come over and use it to lay out your mortise the reason i don't like it is because you end up with two lines and what i find it's very difficult maybe it's just my eyes but to try to go in there and chop that mortise by keeping this chisel between those two lines i always feel like i'm sitting on one and crossing over the other i much prefer to come in with a single line wherever i'm going to place my mortise put this on the far side always keeping the bevel on the inside so that it doesn't end up putting a bevel or a v shape on the outside i would come in there draw a single line between the two ends of my mortise now i can come in and i only have to work to one line and maybe it'll help you too but i find it so much easier to work up against one line than to try to drop that chisel down between two now the next tip follows right along with this if your chisel has square sides and you've kept the end of your chisel nice and square this little tip will really help and that is i'm going to come in here with my square and i'm going to draw a line on the end of the mortise and then at about depending on the species of wood about eight every eighth of an inch i'm going to draw a perpendicular line coming from that gauge mark and i would go all the way down now holding my chisel and setting i i can't eyeball the side of this chisel to keep it parallel to that line but what i can do is i can put the tip down on that line being careful to be right up against this side line and if my chisel is square when the edge is sitting on that line then i know the side is going to be parallel to that line so i can put that right there make my chop and then with successive chops i can either set it right here or i can usually guess meaning i don't have to put a whole bunch of lines on there i when i'm that close i can guess and i can tell when i'm parallel and when i'm not but if you make those little lines you'll find that it's a whole lot easier to keep that chisel so that the side is parallel to that long line now here's a tip that will really help particularly if you're not confident about doing these freehand what i'll often do is take a block of wood that i know has a square edge on it i'll come in here and i will place it in fact it's often good to just come in here and use that same gauge to do it like that so that you know you're getting this block of wood perfectly parallel to that line and then i can come in and using a couple of clamps i can hold that in position now if you're going to do this you want to make sure that you clamp this well you don't want it to move on you hey if you like this video we have more our monthly newsletter has subscriber-only content discounts monthly on tools and anything we bring out that's new subscribers get first crack at it click on the link below let's get back to work now with that clamped in place securely there's another reason why you want the sides to be square instead of having to worry about keeping this plumb you can simply go in there keep this squeezed against your fence chop and then just keep going you don't need to draw your lines in this case this is the best way i know to keep nice square sides and the smoothest possible wall on your mortise now you always need to make sure your mortise is chopped deep enough so that you don't bottom out before your shoulder come up tight it comes up tight but there's also going to be times if you're chopping something like that you don't have a whole lot of depth here so you've got to be careful not to go out all the way through so what i'll do is come in here with a sharpie because it's easy to remove after the fact if i knew i could only go to that line then i would simply draw a line on the back side and then as i go about my chopping i can simply go until that line is right in line with the face of the surface and i don't have to worry about going too deep or not going deep enough i find this next tip really helps when you're chopping in really hard woods now here's my mortise this is the end this is the end so i'm going to purposely avoid chopping right to here so i'm going to start on this one or i'll start up here actually now what i'm going to do is i'm going to chop a series of very shallow mortises it doesn't take a lot of work but what it'll do it's going to give me a little trough and i do this because often times in hardwood you're really wailing on the chisel and sometimes it wants to slide left or right and that's not something you want to have happen but if you start with just a little wee narrow trough i'd go all the way down and then i actually prefer to use one chisel smaller to go in here and just get rid of that little bit now as you come back to get more serious and hit it harder when you set your chisel in it's in between two walls and it keeps it from sliding one side of the other it's a lot easier to keep on that line now the next tip is personal preference but i think there's a little bit of method to the madness here and that is i prefer to use a round what we might call a carver's mallet and the reason is now i typically wouldn't use a rubber mallet but a hammers type it's too easy to glance off one side or the other i don't know but i find with a carver's mallet i never miss i don't even have to be looking at it and i also want it to be a good solid piece i don't want any rubber on here i want to deliver all of the impact i don't want the head of the mallet covered and covered in something that would absorb the impact instead of delivering it and i like it nice and solid because it gives you good feedback and you can tell whether or not the chisel is doing what you want it to do and definitely not bouncing so good carver's mount like that i think you can hit over your head you don't have to look and it always seems to strike just where it needs to okay let's take all those tips and see if we can't cut a nice quick mortise my chisel is nice and sharp back has probably been properly prepared it's nice and flat sides are square to the back now i'm going to come in here and i'm going to draw one line which will be on the left side about that long now i'm going to come in here and define the ends and then i'll give myself some perpendicular guidelines to set my chisel edge on to keep the side of the chisel parallel to that gauge mark now hold it like this so that i can see plumb i'm going to stay away from these outside edges so that i'll do that at the last and hopefully i'll keep the outside perimeter nice and sharp now okay oh we need to do our depth poplars medium dense medium hardwood so i can leave about that much without fear of of telegraphing so i'll put my gauge line on there make it easy to see so i'm going to start on this first line now i'm going to cut a little shallow trough first i find particularly in hardwoods that sometimes the chisel wants to slide so if we just go in there and just do a little a whole bunch of small chops remember i'm not necessarily in a hurry i want to favor accuracy over speed when i'm doing this for fun up against the bench dog i'll take a narrower chisel turning it upside down so that the bevel is down stay away from those outside lines bless you now i can set my chisel in the air it's going to allow me to hit it a lot harder again i'm getting away from that outside edge but that little trough is going to keep that chisel in line now i want to get to depth as quick as possible and on something like this wood i'm going to go about a fat 16th and not ready to pry yet this one i should be able to like operating a bolt on a rifle that allows the chisel to do what it wants you're just applying forward pressure not to the left or to the right and as i chop the bevel pushes the chisel this way and these nice sharp edges sever those fibers and keep that wall nice and clean i'm almost down to depth now as i push this these fibers come out it's really quite easy okay i'm at depth now and i don't bother to clamp my piece in anything smaller i might but your force is straight down so it really isn't going anywhere once you're to depth every chop is quite easy because you just go all the way down and you just take out these chunks of wood and it's really quite fascinating how it happens okay now i'm almost adept so i'm going to turn this around and i'm going to start if i look at that ramp from here to the bottom i'm going to cut it in about three pieces and this is where you want your chisel to be nice and sharp now i'm not up against my line so i can easily pry and that'll just break those fibers free come up another third down to the gauge line pull back and still pry now i'm on my gauge line so this time i cannot pry what i'll do is set the mark set the chisel edge right on that mark keeping it in line with the side start chopping turn this block so that i can see plumb in this direction and hopefully the sides will keep the chisel plumb this way go down right to my depth mark just free enough to free it up pull that out now that was a little bit deeper and i could get that crest in down below the surface i could then pry this way but in this case i can't i don't want to munch that line now what i need to do is go back this way actually i think i'll turn it this way and just keep chopping i don't have a lot because i was almost at my line by the way when you're doing this you want to make sure you're never chopping over a dog hole and you'll blow at the bottom if there's any risk at all going out i'd have a block underneath but i know if i follow my gauge i'm going to be okay now to finish this i have it facing me again i'll split that ramp in thirds down to the depth mark still not on the mark now last chop set the chisel so it's right on that gauge line get it started turn it sideways so i can see plumb in this direction just enough to break it free now i can go in and use a narrower chisel i'll just pry against my hand these fibers for the most part are already cut free they just need to be um they just need to be pulled out they're just more or less wedged in there they're not really connected to the to the bottom or to the side now side balls don't look too bad i could if i wanted to take a beveled edge chisel and just go in there and get rid of some of that fuzz if i still had bumps in there i have two options i could take a marking gauge set it to depth i need one to have a smaller a smaller blade no that one's good set it to depth go in there and i could actually use it as a means of re-freeing up any fibers on the bottom to get rid of them and also as a check to make sure i'm going to have the full depth i need for my tenon or i could shorten my tenon a little bit instead of having to go back in and do a whole lot more work with this but if i had a mortise to chop on the edge of a board i'd almost always now use a block to come in there and hold it hold it to support the chisel and keep it upright it's so much easier but when you get out into the middle of a large piece it's not so easy to clamp a block in place so there's going to be times when you're going to have to do it freehand but as long as you follow those tips you should be able to pull it off and get something that you're proud of no one will ever see it anyway unless it fails so hopefully you have great mortises if you like my work and enjoy my style of teaching click on any one of these videos and help take your woodworking to the next level i've always said better tools make the job so much easier if you click on the link below the chisel and plane icon it'll take you to our site and introduce you to all the tools that we actually manufacture right here in our shop it'll also give you information on our online and in-person workshops

Channel: RobCosman.com

Views: 59,352

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Id: ZEIdDhVla4s

Length: 28min 38sec (1718 seconds)

Published: Sun Oct 24 2021