How To Design A Laser Cut Finger Joint Box Accurately

what's up I'm Jonathan and welcome to maker tales where I'm sharing my maker journey to help you go further in yours so don't forget subscribe and hit that little bell icon to never miss an opportunity to keep making in this video we're going to be making this little box which is a great starter to understand finger joints and box making with a laser cutter not only that is held together without any glue and won't come apart after the smallest tap let's go to make this little box need to understand the basics of laser kerf for those that don't know what a kerf is it's the material lost in any type of cutting process I will make an in-depth video in the future about laser kerf if that's already out is in the description every single material you cut will have a slightly different laser kerf so first decide on the material you would like to make this box out of there are many ways to find your laser kerf my preferred method goes like this I cut a square which on my computer is exactly 20 millimeters by 20 millimeters once cut I make sure to mark the orientation of how it was cut I do this because some lasers and materials cut differently depending on the cutting direction ie the axis that the laser is moving on from here I use my calipers to measure this freshly cut square I get 19 point 8 5 millimeters and luckily for me it's the same on both the X and of Y so together the kerf from this number it's 20 millimeters minus nineteen point eight five which is zero point one five millimeters now we need to divide this number by two as we are currently measuring the kerf that was taken away from both sides of the square doing this leaves us with zero point zero seven five millimeters with this new information we now know we lose zero point zero of 75 millimeters of material on either side of our laser cut line from this point it's a little bit of trial and error now I create three finger joint tests one using a kerf of point zero of seven millimeters another one of point zero seven five millimeters and lastly one of point zero eight millimeters to create these test files you can use your preferred vector creation tool I like using rhino3d I first create a simple finger layout which each finger is a minimum of ten millimeters wide as long as the material is thick if you go smaller than ten millimeters wide per finger you may skew your results due to the material giving way to the pressure of the adjacent finger once you have this basic shape you can then add the new curve value into the mix for example I'll be using my point zero eight millimeters in this one as my other two tests are already made to add this value the way I go about it is I think of it as expanding each finger to fit into its joints everybody does curve Corrections slightly differently some people like to apply it to just one side some people like to do it to both sides I personally like to do it to both sides I select all the anchor points that need moving in one direction and move them all at the same time by my point zero eight millimeters and then I go and do the same for the other side one thing I like to do before putting this to cut is I add little kiss cut lines to them to distinguish one from another now that these first test pieces are made let's get them cut when it comes to the pressure fit results of this test it's hard to explain what we're looking for as it's something that will come with experience but if I had to explain it I'm looking for a good fit not a tight fit the reason for this is that once you have this kerf correction in the layout of a box structure there are going to be many more finger joints fighting against your forces along with other forces such as twist and warp of the wood thus if you pick a joint that is too tight there is a high probability that you can break your box or chip your wood while together out of my tests I'm happiest with the point zero eight millimeter one now that we know this I personally feel that the hardest part of most laser designs is now done when it comes to box designing there are two ways to go about things now that you know your kerf you can use an automated solution like make a box .io personally I like to have full control over my box designs so let's go make one all you really need now is some dimensions for your box plus some sort of idea of how you would like it to look I'm going with an internal dimensions of 90 millimeters tall 70 millimeters wide and 70 millimeters deep with a very simple pull up lid in essence all finger joint boxes are made of three parts not including the lid which are two (A) sides and two (B) sides with a bottom piece interlocking them all together I'm going to show you my preferred box design style which lets you hold a lot more weight inside of an unglued box but please keep in mind that there are many different styles out there to keep things as clear as possible let's grab the two side pieces a and B let's add the unsized to each one now before uniting them let's resize the width of each finger where they need to be resized using our kerf joint value an extra step to keep the Box corners as flush as possible is to also resize the length of the finger by the original curve that being point 0 75 millimeters once they're all resized mirror these fingers over to the other side unite these and that is sides a and B almost done when it comes to joining the bottom to the sides I prefer pin joints rather than finger joints to make these pin joints I'm going to first add two holes to both the sides I'll be keeping the holes a minimum of 3 millimeters from the bottom edge and taking note of the exact location of where I place them I will also shrink these holes by the joint curve value but I will make sure to keep a note of the original width now on to the bottom piece I will be adding fingers or pins to fit into these holes making sure that they are exactly placed and expanding and lengthening them by the kerf values as well once these are united the open box is designed to finish things off now let's get onto the lid taking a look at our box from the top view we know that the internal dimensions are 70 by 70 millimeters starting with this 70 by 70 we will offset this by a value of 0.5 millimeters inwards I do this because working with zero tolerance for moving parts is a little bit too risky sometimes I'll also offset the 70 by 70 curve by 3.075 millimeters this is the material thickness plus the kerf finally let's add a hole in the middle to lift the lid up from deleting the original curve we are now left with a lid that would fit on top of the box and an interlocking piece that would go under this lid you could glue these two together however to keep this build without glue we are going to need to use pin joints once again let's add four small holes where these two pieces will be joined together with once again shrinking the holes with the kerf values and separating the two lid pieces all that is left now for this design is some pins these pins will be just over six millimeters long as it's going through two layers of 3 millimeter wood plus the kerf value on each side of the pin so in total these pins will be six point one five millimeters long as for the width my original hole is 10 millimeters plus adding the kerf joint value to each side gives me a width of ten point one six millimeters lastly I will give the pins a small 0.5 millimeter filet on the bottom side to make it easier to insert these pins into the holes in assembly after coping the design over and the pins and nesting at all let's get it cut out once cut I give it a light sanding then it comes to assembly it should all pressure fit together some very precise rubber mallet in can come in handy for some extra persuasion if needed and following all of those steps you will come out with their lovely little box on top of that you've learned how to master a kerf on the one of your materials and from there the sky's the limit I'll be showing you how to make it this little box of the foundations of that which is a little twist locking mechanism of box from there you get as complicated as 15 step puzzle boxes all this is coming and much more so make sure you subscribe hit that Bell icon thanks for watching keep making and let the quest continue

Channel: Maker Tales

Views: 59,176

Keywords: glowforge, laser basics, lasercutter, laser cut, laser, box, boxes, laser kerf, finger joints, pressure fit, plywood, how to, made on glowforge, box assembly, laser engraver, guide, tips, pin joints, perfect joints, strong, perfect, accurately, rihno 3d, design, tight fit laser box

Id: FBSQGHBpBWg

Length: 10min 29sec (629 seconds)

Published: Fri Jan 10 2020