How to plan segmented bowls for the LATHE

all right everyone in this video i'm going to explain to you how we plan a segmented bowl [Music] you can have all kinds of variety in patterns in segmented bowls the idea of calling it a segmented bowl is simply that it is a bowl comprised of these segments that make the rings that get glued together to make the shape of a bowl segmented bowls can have a variety of patterns and shapes if you use different types of wood to make up the segments you can have a lot of creativity with the different patterns you can come up with in a segmented bowl that you can't with a solid bowl because it's a bunch of pieces kind of like a puzzle being fit together you can create a lot of really interesting patterns now you could just do a solid color one color like this one where it's just a bunch of pieces that are all the same wood and from a distance it almost looks like it was all carved out of one piece of wood but when you get close you realize that it's segments you can have a checkered pattern you can have a lot of pieces combine out different you know if it means cutting a lot of pieces to make a pattern even like this one where there's a piece of wood glued in between each layer to give it this sort of stair look checker pattern inside of a vessel like this whatever the idea whatever the design that you're coming up with you want to brainstorm a bunch of ideas right so i have my i have a brainstorming sheet here that i did just coming up with a few ideas for a bowl regular bowl shape but with a with an alternating pattern on the top similar to this on the top ring another design close to that this one kind of having an idea of if there were you know one dark piece and then below that three dark pieces and then below that one dark piece that would give you that would give you that pattern just a solid stripe you a thicker lighter wood and then a thin stripe underneath kind of like how this one or this one actually this giant bowl kind of like how this one is with these uh solid lines there or a combination of the two i don't know came up with a few ideas this is the one i landed on that i wanted to do for this video for this sample uh just going to be uh not going to be big this is going to be a small bowl with this feature ring in the middle to have a lot of segments because i want to show you when we plan this out many of these like this bowl is each ring is 12 segments but you don't have to use 12 segments you could use more this bowl the pattern if you glued a darker wood outside of a lighter wood and had it facing out when you turn it you get these little swoops and waves but you got to get it right on the center right comes out looking kind of funny today i'm designing with the general cedar point pencil made in jersey city i'm going to show you i have an example here's a completed example of what a bowl plan would look like we have a drawing of the bowl life size scale and then we have this chart that's going to keep track of all the pieces that make up the each ring because remember when we're gluing up a segmented bowl we have rings glued together and then each ring glued to each other so it becomes a lot of pieces if you have especially one like this you can imagine how many each one of these pieces plus the piece in between it can get a little bit crazy to try to keep track of so that's why we have the chart for the plan so i have a life-size full-scale drawing of the bowl here that i highlighted in sharpie so it's a little easier to see on the video and this is life-size so when i'm done this is exactly how big the bowl will be you can draw i would recommend most people draw full-scale uh plans because on a sheet of eight and a half by eleven graph paper if you drew a full size that's a big bowl but if you drew half like a profile like i'm going to show you right now on a piece of paper this big that's a huge bowl so full scale is the way to go so here's how i drew it i got my ruler i'm going to draw the base but i'm going to draw a profile because this is all that we really need is a this is the whole bowl but to get this shape right here that's this outer shape of the bowl and you don't need to draw the entire bowl to get this is the this is the outer shape that we're trying to mask you know get uh you can see the difference in the outer shape between these two so we need to arrive at the design the pattern that we're looking for there and in this case it's just a subtle swoop out and i have this curved upper ring so i would just draw this swoop going down and that's my outer outside profile and i only need half the bowl drawn because in order to get my measurements because the other side is going to be a mirror of this you can imagine it's spinning on the lathe you only need to know half of the of the design so the top ring i'm going to make three quarters of an inch thick and i draw that line to show where that's going to be the bottom the bottom of segmented bowls is just a solid circle so after we have our rings we glue the solid circle to those rings and that becomes the blank that we turn so that's going to be a three quarter inch piece of wood as the bottom and then i have this half an inch uh space basically right there in between the two and i might cut into the bottom here a little bit as well we also need to think about the inside shape this uh the wall thickness so we can have this consistent wall thickness of the bowl all the way down so i'm going to imagine this on the inside i'm going to make a small little rounded edge there and then i'm going to match that outer profile that outer shape cutting down into the bottom about that so that's going to be basically the thickness of the walls of the bowl and the outside dimension and then i have this pattern here now in order to get the chart i'm going to give you this segmented bowl plan and you can draw that on here but if you if this is too small you can do it on a regular graph paper but here's the chart what's critical for the chart is the ring number that's how many layers each layer ring one two or three the diameter of that layer the segment angle the number of segments the width of the segment the height of the segment the length of the segment the board length how much wood you'll need and any notes or material that you'll need to include in there so from this sketch from this drawing and this final drawing here is where i'm going to draw my my detail for this feature ring right i have these i have these eighth inch strips there and then we're going to make maybe quarter inch thick segments close to that so that's basically all you need to get a basic idea of what it is you're going to make and there's the final drawing so from that i can get the measurements i need in order to glue all the rings and for this you will need the the chart the segment bowl plan chart which i'm gonna i don't need this graph paper so i'm gonna fold this over just for the sake of seeing it and this segment reference sheet this is gonna have everything you need on the sheet for you to calculate everything you need it has these um it has conversions from decimal to fraction and it has the formulas that you'll need for each one of these uh these calculations now we're gonna have to do some math don't run away it's okay though this is not too hard we're gonna have a calculator so from our drawing this is the most critical thing to have is the drawing we're gonna take all of our measurements from this and transfer it to our planning chart so i'm gonna label each ring the top ring is gonna be ring one the second ring is gonna be ring two which is gonna go from it's gonna be the whole feature ring it's gonna be all from here to here this whole middle section is going to be the second ring then we're going to have a third ring here which just for the sake of argument i'll make that whole thing you know what so actually i'm changing my mind that's going to be three quarters of an inch also and then we'll have the bottom which might go that low but we can cut it off later and that's ring four so it's going to be three segmented layers and a solid base so the diameter that diameter has to go from the center point to the farthest point on the bowl to get the radius i could measure the whole drawing here at the top if i had a scale drawing full size but if if you're only offer operating off of a half drawing like this we'll just take the radius so i'm going to measure from the middle to the end of the bowl the farthest point on within this first ring and my radius is three and a quarter which means six and a half which i can measure up here and i can see six and a half so ring number one's diameter is six and a half inches which i wrote right there and i'm gonna do the same thing for ring two from the biggest point the farthest point to the center ring three the same thing from the farthest point in on that ring the biggest part of that ring and in this case three and an eighth so not much smaller six and a quarter but it's going to taper all down and we're gonna get to that later so ring three from the center to the edge is two and three quarter so that's five and one half and then the base the solid circle is um two and a quarter so four and a half so the radius being two and a quarter i double that to make the diameter and that's four and a half radius times two is the diameter and you write the diameter there next you need to calculate the segment angle and that we can find on our reference sheet right here segment angle 360 divided by two times the number of segments so you need to decide how many pieces is going to be in each layer now because this top layer and the bottom layer are all going to be one type of wood there's no need to do a specific number of pieces because there's no pattern so we could do eight segments we could do 12 segments those are the two basic standard ones i like to work with 12 because like i said this bowl each ring is 12. this bowl each one is 12. 8 and 12 already have presets on the miter saw 15 degrees and 22 and a half degrees which we'll get into in a moment so if you're working with an eight segment ring versus a 12 segment ring you can see the difference in how round they already are so the more segments the more round it begins to it begins with and that's less work on the lathe it also means less scrap and less to worry about when you glue the layers together so if we look at these rings i put these drawings on here you can see how thick of up that's how thick the wall can be of the inside of the bowl once it's round on the inside and the outside but all this becomes scrap and on the 12 segment you can see far less becomes scrap so in this case i'm going to do 12 segments eight segments is possible though too so we're gonna decide on this top ring and this bottom ring that it's gonna be 12 segments ring one and ring three is 12 segments so to get the angle we look at our formula chart 360 divided by 2 times the number of segments 360 divided by 12 times 2 24 divided by 24 15 degrees because this angle this one shows it better that's one segment you can see the 15 degree angle cut and when those are all glued together 12 pieces it makes a circle so 15 degrees for rings one and three now we need to calculate the segment width this here is the width from here to here how wide does it have to be in order to be glued to the next layer with enough overlap that you have that thickness in the wood when you get on the lathe because you don't want to be on the lathe and end up with something way too thin you want to have a nice you want to have the planned amount of thickness in the walls here if you make the overlap too small it won't be round or smooth and if you make it too big you'll just have more work to do so it's always better to overestimate so for ring one we're going to measure from this outermost point the full thickness of the uh of the bowl that we planned plus i like to add a half an inch to that and i'm going to plan out the width of the second ring while i'm here i'm just going to draw my line straight down from the farthest point i go across the whole bottom to the over from the overlap to the of the thickness plus a half an inch that's my middle ring so that's my width right there i can just measure that distance the top ring is one inch i need one inch wide to make that size then the middle ring has to go from way out here to the to the next transition on the third ring so that one is one and three eighths one inch and three eighths and that has to be that wide because of the shape we're swooping down like cutting down that whole ring so let's be thick to get this to get this profile and then the one below that one and a quarter so i'm just measuring my width so if you imagine that's the ring there's the width right there how thick it has to be and you need at least a half an inch extra at least i like to put a half an inch extra because then i know i'll have enough surface between the layers glued together to make sure that i have that thickness and enough to hold it all together when it's spinning on the lathe all right so i have my width now i need my height height is pretty easy because we already calculated it here with these one two and threes so i can look at my graph paper actually and count this number one is three quarters of an inch high two one two three four four that's an inch high three is three quarters of an inch high and then the fourth one is three quarters of an inch thick now the fourth one we already got the diameter but we don't have a number of segments or angles so that's just solid so i'm just going to write solid here because there is no segment width the segment width is this is this is one big piece one segment the whole thing so solid now the complicated one is the segment length in order to do the segment length we have to do the rest of these formulas in our formula chart here's our segment length we need to know the circumference the circumference is the distance measured from here all the way around back to the beginning how do you figure that out that's this formula up here diameter times pi or 3.14 you know the diameter because you measured it before we measured our diameters here so we break out our trusty calculator and we can write six and a half 6.5 times 3.14 and that gives us 20.41 so i'm going to round up 21 inches is going to be the amount of wood i'm going to need and i'm going to write that over here in this board length so number one i need 21 and i need and i'm gonna add six inches just to be safe so we'll probably cut for that ring 27 inches or 26 inches now that i have my circumference which is 20.41 i'm just going to make a note of it there in the board length chart i know my circumference i can do the segment length formula circumference divided by number of segments how many segments did i put in ring number one 12. so i take that number while it's still on the screen 20.41 divided by 12 and that gives me 1.70 and that's where that will be so this from here to here that's our segment length we need to know that length that's going to vary based on 12 segments or eight segments that's why the formula is circumference divided by the number of segments because when we cut this out the distance from this outer point to this outer point has to be 1.7 and if it is it will make a six and a half inch circle because this is 1.7 plus 1.7 plus 1.7 and so on and so on obviously the calculation would be a little different for an eight segment or even more which i'll show you in a minute when we do the middle ring so 1.7 let's do the third ring diameter times pi will give us our circumference 5 times 5.5 times 3.14 17.27 so i'm going to round up to 18 inches for that 17.27 divided by the number of segments 1.44 it's actually 1.439 but we're going to say 144. so that means that to get a diameter this big we need segments that are 1.7 long to get a diameter this big down here this is obviously going to be smaller not 1.7 but 1.44 so here's our segment and the next one might be a little bit smaller like that obviously 12 of these is going to make a sm a smaller circle than 12 of these so there's our segment length now let's do the middle one the middle one here i want to do a bunch of these little skinny skinny pieces like this so i could do 24 pieces i could do 18 pieces i can do whatever i want whatever size i feel like making in there because of these because of these formulas and since i want them to be close to a quarter of an inch in segment length let's just experiment with different sizes real quick to see which one is going to work out diameter times pi first 6.25 because it's six and a quarter diameter six and a quarter so 6.25 times pi is 19.25 625 19.625 always around up to 20 inches for that to make sure we have 20 inches of wood for that 19.625 if i were to do 12 segments each one would be an inch 1.63 inches way too big 19.625 divided by 80 pieces 0.4 2.4 0.24 wow 80 segments in the middle 80 pieces so what's our angle 360 divided by 2 times the number of segments 80 times 2 160 360 divided by 160 2.25 degrees so if we cut a segment at 2.25 degrees and we have 80 pieces we will get this thin quarter inch ring all the way around future me interrupting this planning phase for an update on the plan turns out i don't actually have a way of cutting two and a quarter degrees uh anywhere but on the jig right here the incra miter 3000 i can cut a two and a half degree angle on the table saw which if i look at my chart and i change that from two and a quarter to two and a half degrees it means 72 pieces of wood will make up that feature ring in the center but now i can give you a preview of what the wood will look like for that ring so that's 72 pieces in that ring to get a two and a half degree angle instead of two and a quarter sometimes we've got to make these changes on the fly the purpose of this fractional this i have this this this fraction decimal chart um i'll give you one or you can download one from anywhere because the internet they i have them posted everywhere in the room very easy to just quickly reference because we do math with decimal and we want to change it because decimals don't appear on the ruler so how far is 1.7 we look at this to 0.7 45 sixty-fourths well that's a sixty-fourth bigger than eleven sixteenths so i'm gonna make that my measurement one and eleven sixteenths so then my segment length for that piece is gonna be right there one and 11 16 right there on the ruler 0.24 obviously is a a shade smaller than a quarter inch so there's quarter inch 0.25 but 15 64 is 2 3. so it's not even a 64th smaller so we're going to make it a quarter inch because that's the easiest landmark on the ruler to go to and 1.44 is uh basically seven sixteenths one point four three so we're gonna make that one and seven sixteenths so we're rounding up and down a sixteenth of an inch based on the number and that's why we have so much extra in the width we're not gonna have to worry about it doesn't have to be that exact but we do want to have enough wood to go around the whole ring and have enough to glue to the layer below it so that it stays strong so that is our plan i'm going to follow this chart to create this bowl we need to go pick the material that we're gonna use i can put that in the notes here maybe maybe some cherry and maple will be nice i'll have to see what combinations look good but that will be the plan alright everybody let's get started [Applause]

Channel: Michael Campbell

Views: 1,470

Keywords: woodturning, wood turning, lathe, segmented

Id: ch1poYBsDd0

Length: 25min 17sec (1517 seconds)

Published: Tue Mar 22 2022