Howto model Bridle Joints in FreeCAD

for this demonstration i'm going to use freecad version 0.19 which was built on the 26th of may now the three bridal joints we're going to model today are the quarter bridle the t bridle and the mitre bridle the joints are very similar and i'm going to use this as an opportunity to try different techniques of modelling first thing i'm going to do is create a spreadsheet that contains the common parameters used by the joints so create the new spreadsheet we'll switch over to the spreadsheet workbench and create a new spreadsheet the names of the parameters will be stored in column a and their values in b now in order for you to use these parameters in a model we need to create aliases for them in column b so you can either do that by clicking on the column and then clicking on the set alias tool and i'm going to make the alias the same name as the parameter you'll see that the background of the cell is yellow indicating that it has an alias the other way to do it is to use a macro which allows you to set up multiple aliases in one hit so what i'm going to do is select all the parameters and then i am going to run the easy alias macro but before i do that i'll just quickly show you how to get it and install on your system so you click on the tools menu go to the add-on manager and what this does is allows you to install new workbenches and or macros so we'll click on the macros tab we'll go get the list of available macros and then we simply scroll down until we find the one we want we click on it and when it's downloaded all the information you can click install update now i've already done that so i don't need to do it again now that i've done that i can run that macro so go back to the macros menu go to the list of macros click on easy alias and then click execute and that has set up aliases for all the cells now we're just going to add some values now i'm going to save this because i'm going to use it as the foundation of all the parts i'm about to design so we go to file and click save as then we navigate to where we want to save it and i'm going to call it specifications we'll close the spreadsheet down because we don't need that anymore i'm also going to save another copy and call it common style because this is the style i'll use uh for the corner and mitre bridle i'm going to switch to the part design workbench and from there i'm going to create a new part and get a body to it and then i'm going to create a sketch sketch will be in the xz plane zoom out a bit now the style is a vertical rectangle so we can create that using the rectangle tool either by clicking on the icon or pressing the r key and i'll just press the r key now i want it to be symmetric around the origin point so i'll click the top left corner bottom right corner and the origin point and apply a symmetry constraint by either pressing the s key or using the tool in the toolbar so i'm going to use the s key i'm going to set the height of the style using a vertical constraint which is this icon up top or you can type in shift and v and because we're going to use this value in the spreadsheet we'll enter the formula editor by pressing the equal key or clicking on that icon there and we will you set it to be this dial length click ok and we'll do the same sort of thing for the width of the style by using a horizontal constraint so we can do that by pressing shift h or clicking on the tool in the toolbar i'll use shift h and we'll use the formula editor to set the width so you start with now that it's a fully constrained sketch we'll close it and we'll use the pad tool to make it into a solid but before i do that i'm going to change over to the isometric view which is how i prefer to look at a lot of these models and then i'm going to fit the view to the page by pressing the v key followed by the f key you could also do that by pulling down the view menu and going to standard views and then fit all now we're going to create a pad so we'll click on the pattern tool and we're going to use the thickness of the style from the spreadsheet so we enter into the formula editor and we use the style thickness and i want the style to be symmetric to the origin plane so that there's equidistant across either side so i turn on symmetric to plane and click ok now what i'm going to do is create the slot for the tenants in the rail so to do that i'm going to create a datum plane i'm not going to associate it with any geometry at the moment i'm just going to leave it associated with the origin choose nothing in the parameters and just click ok and that will put it right on the origin now it's just warning me that i haven't done any references and that's fine so i'm going to click yes then what i'm going to do is i'm going to switch into the model view and click on the datum plane so i can change its parameters in this case what i'm going to do is change its position in the z axis so i click on placement followed by position and then click on the z-axis or z-coordinate and if i make it bigger you'll see climb if i make it smaller you'll see it go down now i'm going to set its position in the z-axis using the formula and that formula is half the length of the style and when i refresh it it moves it to the top now i'm going to create a sketch that uses that plane and in this case i'm not going to bring in any external geometry i am simply going to place a rectangle representing the slot and make it symmetric around the origin point and then set its extents so i do that by pressing the r key which will give me a rectangle i put it roughly in position i make it symmetrical by picking the top left bottom right and middle point and pressing the s key i then set its length with a horizontal constraint by pressing shift h and using the formula editor to set the style width and then i set the height of the the slot using a vertical constraint by pressing shift v and use the formula editor to get the slot width and that's a constrained sketch so we can close that and now i'm going to use the pocket tool to make the slot depth the same as the width of the rail so click on the pocket tool we're going to use a formula editor to get the rail oops the rail width click okay save that in fact we'll turn off the datum plane first by clicking on it and then pressing the space bar save it again so that's our common style close that one down now i'm going to create a rail for the corner bridle so i'll open up the specifications model and then save that as corner mitre rail i'm already in the part design workbench so i'm simply going to create a new part then a body and then create a sketch again we'll do it in the x z plane we'll draw the rail as a horizontal rectangle by pressing the r key and then picking the points it will be symmetric around this center origin point and we'll do this using a symmetric constraint pressing the s key we'll set the length of the rail using the horizontal distance constraint by pressing the h key sorry the shift h key and use the formula editor to get the rail length zoom out a bit and we'll set the width of the rail using a vertical constraint by pressing the shift v keys and get the rail width from the spreadsheet using the formula close that will fit to view by pressing v followed by the f key and then we'll pad it out to be the thickness of the rail again we want it symmetric around the plane and we want the distance or length of the pad to be the thickness of the rail which is in the spreadsheet so we press the equals key to bring up the formula editor and get the rail thickness straight out of the spreadsheet now we will create the tenon at the end so this time we're going to create a datum plane on the top face and i'll select the face i'll create the datum plane and then i'm going to disassociate it from it i'm doing it this way to try and avoid the topological naming problem i've linked a video at the top if you'd like to learn more about that then go into creating sketch and reference that datum plane and then i'm just going to place a rectangle for some reason the underlying part hasn't shown up so i'll just close the sketch so i can see where i've put it and then i'll reopen the sketch by double clicking on it and now it's come in maybe it's a bug i'm not sure so in order to model the tenon i'm going to model the waste which will be removed and leave the tenon there so to do that i'm going to use this rectangle which represents one side of the waist i'm going to use a vertical distance constraint to set the upper limit of the waist and the distance is going to be a half the thickness of the rail so we so we press shift b and then enter the formula editor by pressing the equals key rail thickness divided by two we'll set the length of the waist using a horizontal constraint and that's going to be the length of the sorry the width of the style and we need to fix the end of the the waste to the end of the rail so we'll do that with a horizontal constraint we'll use the origin point and the top right corner of the waist use a horizontal constraint pressing shift h and it's going into the formula editor to set the formula to be half the length of the rail the only thing remaining is to determine how high the waste is going to be and to do that what we're going to do is use another formula and because the thickness of the rail is less than the thickness of the style we're going to determine the amount of waste to remove by a formula which is the width of the rail minus the thickness of the slot in the style divided by two and that's not quite right what did i do wrong oh i would rail with it's the thickness of the rail not the width that looks better what that formula will do is if i change the thickness of the rail it will automatically recalculate the height of the waste and leave the resulting tenon the same width which is what i want so now we've got a constrained sketch so i'll close that and we will use the pocket tool to remove the waste and then we will mirror that on the other side to reveal the tenon so we use the pocket tool and we're just going to push the pocket all the way through click ok so now we're going to mirror it we select the pocket we click on the mirror tool and we're going to click on the base xz plane to remove the second side of the waste and click ok which leaves us the rail with the tenon and turn off the datum plane because we don't really need that now and save that now we're going to do a quick assembly of this so we'll create a new drawing we will save that as corner assembly and we will switch to the a2 plus workbench and we'll import the common style and we'll import the corner miter rail which is badly named because it shouldn't be a miter and now we're going to bring the joint together by making the appropriate faces coincident to each other so i click on a face on the tenon i click on the corresponding face in the style and i use the plain coincident constraint click yes accept switch back to isometric view fit and you can see that that has aligned it front to back now we need to align them vertically so we click on the bottom face of the rail and the bottom face of the style the slot and then use the same constraint the plane coincident constraint and click accept and as you can see they're now aligned vertically front to back but not left to right and the problem with the way it is at the moment i'm going to find it difficult to get the access to the faces i'm going to click on the rail and i'm going to use the transform tool to pull them apart temporarily like so and then i can select this face on the shoulder of the tenon and then i can select this face on the rail make them coincident and everything is where i expect it to be so now we're going to move on to modeling the rail for the t-bridle joint i'll close those i'll reopen the specifications model and i will save that so i'll name this one correctly it is a t bridal rail not a t mitre rail we switch back to the part design workbench we create a part create a body and then a new sketch again it will be in the xz plane the t bridle will have the waist cut in the middle so we will create a new datum plane without any references it's fine we will again move its position to be half the width of the rail or move the move its position by half the width of the rail so we get that from the spreadsheet refresh the view then we will create a sketch and use it in this case i'm going to just place two rectangles somewhere near the center we'll fix that up shortly close that and then reopen the sketch to see where they actually went all right so we're going to do the same sort of process the vertical distance from the origin point to the top of the waist is half the thickness of the rail so we do that using a vertical constraint by pressing shift v then go into the formula editor by pressing equals and defining that value rail thickness on two okay the waist is also symmetric around the vertical axis so we select the two endpoints and the vertical axis and place a symmetry constraint by pressing the s key the height of the waste is the same in both cases so we make them equal using an equality constraint by pressing e we make the two wastes symmetric around the horizontal axis by clicking on the two endpoints and the horizontal axis and applying a symmetric constraint we also make the endpoints vertical by clicking on the two points and pressing the v key or using the v constraint vertical constraint sorry the length of the two waists are the same so we set them using an equality constraint we set the length of the waist to be the width of the rail so click on the length press shift h for a horizontal constraint enter the formula editor by pressing the equals key and getting the white width of the waist from the style the last thing we've got to do is determine how high it is in this case we're going to do something different we're just going to simply set a vertical constraint by pressing shift v and using the slot thickness defined in the spreadsheet so that is the style slot thickness we now have a fully constrained sketch we can close that and then just create the pocket again it's just going to be pocketed all the way through and we're done we can turn off the datum plane and we'll do another quick assembly just to show what it will look like so create a new model save that as t write all this simply switch to the assembly uh a2 plus workbench pull in the parts and then just start applying coincident constraints again as you can see it is now as intended and we'll move on to modeling the miter bridle joint so close these models down we'll reopen the specifications we'll save that as mitre bridal rail quickly draw that up it's much the same as everything else i've done now we're going to create a datum plane on this face model the triangle which represents the waist that we'll cut away and then we'll go back and create the style so select the face create the datum plane detach it from the face now we'll create a sketch on the datum plane and we'll draw a rough triangle which will fix up shortly close that reopen the sketch so we can put in context to the rest of the rail the horizontal distance from the base of the triangle to the origin is half the length of the rail so we'll put in a horizontal constraint you're pressing shift h and enter the formula editor by pressing equals and get the length of the rail and divide it by two the vertical distance between the top of the base and the origin point is half the width of the rail so we'll set a vertical constraint pressing shift e and use a the formula editor to divide the rail width by two the length of the base of the triangle is the width of the rail so we use a vertical constraint and just get the rail width straight out of the spreadsheet using the formula editor and the length of the triangle is the width of the style so we use a horizontal constraint and then use the formula editor to get the style width out of the spreadsheet then we use a pocket tool to remove the waste and the waste is going to be the thickness of the rail minus the thickness of the slot divided by two so we use a formula editor to do that so it's rail thickness minus dot slot thickness divided by two click ok and turn off the datum plane and now we're going to use the mirror tool to mirror it onto the other side of the rail so we click on the pocket click on mirror and we'll use the base x z plane click ok and save that now we'll move on to designing the style and to simplify things we'll just open up the common style make the necessary changes and save that so we'll open up the common style and we'll save that as miter bridle style going to create a sketch on this face and remove a triangular portion of waste so we will create a datum plane and disassociated from the face then we will create a sketch and we will mock in the rough triangle close it just to make sure we put in the right side and the vertical distance from the top of the triangle to the origin point is half the length of the style so we put in a vertical constraint by pressing shift b then use the formula editor to set that value by pressing equals getting the style length from the spreadsheet and then dividing it by two the horizontal distance from the side of the triangle to the origin point is half the width of the style so we set a horizontal constraint by pressing shift h and use the formula editor to work that out style width onto the width of the top of the triangle is the width of the style so we put in a horizontal constraint by pressing shift h and just simply use the equation editor to get the style width from the spreadsheet and the height of the waist is the width of the rail so we put a vertical constraint and just get the width of the rail from the spreadsheet using the formula editor oops and we've got a constrained sketch so we can close that and then we're going to use pocket and in this case we're just going to push the pocket through everything so we change the type to through all click ok and turn off the datum plane and now we will assemble it so if we create a new model switch to the a2 plus workbench save the model as motor bridle assembly import the rail and import the style now as you can see they're not going to go together very well like this at the moment so i will just rotate the rail 180 degrees so using the transform tool and then just dragging on the right ball the red ball until it comes around 180 degrees and then it's just a matter of applying the constraints as we normally would isometric view and fit it and you can see it's gone together as expected this is the first free cat demonstration i've recorded with the camera running and there's a few wrinkles to iron out but i hope you found that it was interesting if you'd like to support me there is a link in the description below that shows you how to buy a cup of coffee for me this will just go to providing extra resources for the channel and hopefully improve the quality of the work that i'm doing for you if you liked the video please click the like button and please leave any comments or topic suggestions in the comments below please consider subscribing to the channel and clicking the notification bell so you stay up to date with my videos thank you for watching see you next time

Channel: Glasson Design Studio

Views: 1,808

Keywords: wood work, fine furniture, woodwork, furniture making, furniture design, freecad, freecad tutorial, furniture design using freecad, freecad part design tutorial, freecad sketcher tutorial, freecad tutorials, freecad sketcher constraints, freecad assembly 2 plus

Id: 9S6oqKrBmys

Length: 36min 24sec (2184 seconds)

Published: Thu Jun 04 2020