How to use a Sashigane (Japanese carpenter's square)!! Circumference, compound angles!!

[Music] i finally finished this desk for a client that i've been making it has a secret drawer i'll put a link to the video that shows all of that for those of you that saw the other video i want to introduce you to the japanese carpenter square this is called a sashigane there are other words for it but it's typically referred to as a sashigane this one is in units that are traditionally used in japan for building temples etc called sun and shaku so ishaku is ten sun one to ten and it's about a foot long if you play the shakuhachi or if you've ever heard of the instrument the japanese flute called a shakuhachi it's called as shakuhachi because traditionally the length of the shakuhachi is ishaku so if you add ten or ten sun one shaku tour to a eight sun you will get the length of a shakuhachi which is why it's called shakachi and there's your japanese lesson for the day i want to show you this because it's really an innovative and amazing tool this is what they use to build temples with those complicated roofs that you see with the angles going all different directions this is all they use to get all those angles so it's pretty amazing but there are other a couple other features of this tool that are really neat one of them being this measurement right here if you look close you'll be able to see that this measurement is much smaller than the sun measurements up here and the reason for that is this measurement is the measurement times pi so basically what you use this for is figuring out the circumference of a round object so let's take a my ball of tape here not a ball sorry my whatever of tape and um if i measure the diameter of this i get let's see that's five right so i get one two three 3.5 or so i get 3.5 sun okay again this is the japanese units of measurement sun so i get 3.5 sun so let's test this we'll get a pen here and we will put a mark right where the tape ends and now we're going to lay down our ruler make sure we got the sun marks there we go okay so one two three four five soon right i think we said it was 3.5 soon right so now i'm going to take the tape off and i'll open it up put this down here and i'll open it up until we get to that mark oops until we get to that mark that we made right there and if we measure this let's rip that off we will see that it is oh lo and behold one two three almost five sun now i took some of the tape off so the diameter changed a little bit but you can see now that you can measure the circumference of a round object using this scale in here and this scale is the measurement times the square root of 2 if i remember correctly and what that enables you to do actually right here sorry on the outside what that enables you to do is figure out the largest length of a square object from a round object i know that was really hard to understand what i mean is if you have a round object like a log for example let's say this is the end of the log if i'm looking at this log and i'm going to build something with it right so i want to create a square timber i want a square timber but since this is round i don't know the largest square timber that i can get out of this log but with this sashigane that'll tell you what you do is you measure the diameter with this measurement on the outside which i said earlier was the end result multiplied by the square root of two and i'll see that i get 1 2 and let's see 2.3 sun 2.3 sun on this measurement so that should be the longest face that i can get if i were to make a square log and if i flip this over what was it in here it was 2.3 right 2.3 soon so then if i take 2.3 and i measure that one two three we'll see that it's about that long right and if i were to go all the way around 2.3 2.3 you can see now that i'm marking out the dimensions of the largest square timber that i could get out of this round piece of wood like so now this is very crude and i'm doing it on the back of a vintage wax tub here so it's not very accurate but you understand what i'm trying to say so this is how what they would use to figure out the largest timber that you could get from a log now the other thing and actually before i go further let me just say that you can also get these modern ones in centimeters this has the same measurements on the inside here this is your result times pi and then on the inside here you have your result times the square root of two so you can do the exact same thing that i did earlier if i measure the circumference here it says about 10 this is going to be the circumference of this object should be about 10 centimeters so again if i mark that there and let's get rid of this one and if i open that up to where we have our mark and i measure that boom 10 centimeters so that's very handy for figuring out the circumference of an object and again you can do the same thing figuring out the largest square timber from around log but the the most impressive thing about this tool is that you can figure out angles and the way they do that is when they're building a structure they decide on a slope say they're going to do a five sun slope so gosum kobay is what it would be called and what that means is they would place the sashigare down so that the bottom of a triangle that you would make a righted triangle would be one shaku so it'd be tension so from here to here and then they go up five one two three four five this hypotenuse that you get from the five to the ten is your gosun kobay or your five sun slope as they were called let me get some paper so this would be a little easier to see so let's say they decided to use a ghost slope or a five-sim slope what they would do is for the bottom of a triangle i should say they would draw they'd start by drawing a triangle a right triangle with the bottom at 10 ishaku and then 5 so flip that over and it'll go up one two three four five so this is five sun and this is tension or ishaku and then you would connect it to get your hypotenuse and this is your gosun slope now from here they use the sashigan again and these different measurements like i explained earlier they have different measurements on different sides and your main sun measurements are in this side you can see that the short side is the same as the long side in terms of the length of the units if i get a little closer you go to see that they're both soon but if i flip it over you'll see that this remains the same as this side they're both sun but these measurements are longer than these and this is called the urane so well they would go back to this triangle that they drew gosun kobai triangle gosun slope triangle and then since this is ishaku or tensun they would go and they would put the sashigame here on 10 from the urane or the back side and they would continue this bottom part of the triangle out and i ran out just a little bit of a piece of paper there but let's say that this is 10 from the opposite side of sun and then they would connect your hypotenuse if i remember that's what it's called on a triangle you connect your hypotenuse up here right and then they'd go from the hypotenuse of the original triangle and they would draw a right angle from that hypotenuse down to the corner so that this is a right angle this is a right angle over here and then they would figure out half of the side of the triangle so if it's 5 that's going to be 2.5 is going to be your halfway point and then they draw another line from the corner to the halfway mark and then they would again draw a right angle from here to this corner that's a right angle and then half of this let's flip this over here half of this side of the triangle this is about seven so that's going to be 3.5 and then from there to there there's another slope and as we do this again you can extend this this is a gosun on your normal scale but if i flip it over to urame and i measure out five then that extends the line up to here and then i connect again to this one point so what i'm doing is i'm using a base triangle this goes in this five sun slope triangle and then extending the lines and connecting them to the central point to get all these different slopes so this is a different slope angle this is a different slope that's a different one that's a different these are different slope angles and they would record all of these lengths on this triangle so if they decided that a portion of the roof is going to be the slope from this original triangle then when they're cutting their wood what they would do is if we want this slope from the gosun or the gol sun slope triangle they would take the sashigane and they would put one side on ishaku let's say i wanted to have the line here i wanted to cut this wood and have the slope be the slope for that the gosund the gosun slope so i would put the sashi gane at five here and then over on this side i line it up with 10 which if you remember is the length of the bottom of that one triangle and this gives me my five sun slope angle and they would do that for different parts of the roof like i mentioned earlier japanese roofs on temples are very complex if you look here in this book you can see it has different slopes [Applause] this is a better picture you see how all these different slopes are incorporated into the end of the roof and they need to know how to measure each of those slopes so they would create a triangle based on a certain slope angle and then take all the measurements off of that one triangle now you can do the same thing with modern woodworking if you want to build a desk for example that has sloped legs right let's just do a draw the top of a desk all right and let's say you want to draw or i'm sorry you want to have splayed legs on it right well this angle is going to be the same as an angle if you had a an apron on it so you want to have an apron and you want to attach the apron by mortisey and tenon into the leg this angle here is going to be the same as this angle here on the bottom and if you decide that's going to be like three sun maybe a three sun slope then to get that angle to cut that angle on your legs all you got to do is take your sashi ghane and put the three on the end of the board and match it up with ten let's do it this way so it's easier to see [Music] i have my three on that side and then i have 10 over here and now this is that angle so that's the angle of your leg it's going to be on the opposite side and you cut that and it's also going to be the same angle as this apron here that's going to be attached to your leg now i know you're saying well i can't get one of these this is a japanese one in sun and i don't know how to read soon anyway well they also sell ones in centimeters i'm not sure if you can get them abroad but you can also make your own like i did here all you do is take two pieces of plywood and joint them together with a bridal joint and then take a ruler and mark out your centimeter marks or inches or whatever you want to do and then because it's thick obviously this is a very thin piece of metal so you can take the measurement right off the top of the sashigana but if you make your own you're going to have this thickness to deal with so what i did was after i marked off the centimeter marks then i took a a square and i marked them down to the bottom so that when i'm using this on an actual piece of wood if i want to line up to get a certain angle like let's say i want to do a seven centimeter slope here's my five six seven there's my seven mark right there and i can follow that down five six seven follow that down to the edge of the board is there and then make sure that i line up my sashigame with in this case i'll do 30 30 centimeters seven seven on this side 30 over here and then this gives me my slope that i want to cut so whatever i'm making if i'm making a table that has splayed legs or whatever i'm going to use that angle on all of the components and that's it i know it was thoroughly confusing uh it is very very complicated in japanese it's called which is the art of being able to use a sashi gane to figure out all these different angles when you're building the roof of the temple etc and it takes many years to learn i just studied practicing and learning about it over the last year or so but i thought it was neat and for people that use western tools you've probably never used the sashigane or seen it or know how it's used so i thought that would be informative so let me show you an example of how this is used for roofing i've taken the sashigani and i have drawn different angles according to a design in one of the books that i have for making a part of a roof the end of the roof in particular and now i'm going to cut it apart and show you how it all goes together to create those different angles and slopes that we talked about earlier it's very difficult i'm unfortunately not good enough with my japanese saw here to saw correctly as it should be but you'll get an idea for exactly how everything will go together if you uh do everything correctly so uh i'll let you watch the video and thanks very much for stopping by please subscribe if you haven't and click like button for me if you can i'd appreciate it thanks a lot you

Channel: Tenons & Tenors

Views: 27,340

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Id: i__oDChKPzA

Length: 20min 43sec (1243 seconds)

Published: Fri Mar 26 2021