About this 3D model

TL;DR: I recreated a cabinet/drawer knob (Liberty's "Garrett" or “Classic Round” - they are both the same thing). It was a journey. I included a FreeCAD file and additional versions (largely untested) so it can be used/edited for use with with different standard screw sizes (Metric/Imperial) for convenience/versatility. No supports required. This is going to be a long one Read at your own peril. You might just learn something . Why I made it So we've had this knob in our kitchen that has been barely hanging on for literally years now, I think since we moved in. It's just one of the many identical, basic, round metal knobs that were pre-installed in our kitchen (for multiple cabinet doors). Upon seeing that Printables was holding a replacement parts contest, I looked around the house for something broken. I was reminded of this knob as it had recently fallen off the door again. The threading is stripped where the screw enters the knob, so it needs to be forced and then barely holds on. After a little while it eventually falls off when pulled. Between the contest, my desire to continue learning CAD (through FreeCAD), and the need before me… I figured I'd have a crack at it. Disclaimer: I was NEVER going to replace this knob with a 3D-printed replica . While I do intend to print my own replacement knobs, I want those to be more custom. This project served as a huge learning experience for me (and possibly others) in multiple ways, a service to anyone looking for a knob, and an entry in a contest. The contest really motivated me to try to see this through the rest of the way, despite me not necessarily planning to use the knobs as intended in the end. The lessons learned are helpful, and I plan to construct my own knobs and future objects using what I learned here. I have made/posted other things here since my first foray into FreeCAD . But this project was my 2nd unique thing I used it to make. I just hadn't gotten around to posting about it yet. The Process So first thing's first. Here's the knob I set out to recreate, along with the accompanying screw: Measuring I took a lot of measurements of the knob using my cheap digital calipers . I measured 6 different diameters (listed in order from bottom to top): Base Platform b/w base and lower curve Narrowest Point in lower curve (or overall) Platform b/w lower and upper curve Groove in upper curve (I wanted to try and recreate this subtle detail too) Widest Point in upper curve (or overall) I then measured the overall height from top to bottom, as well as the thickness of the base . These I could do properly. I then approximated to the best of my ability the distances between each of the points I had measured in the above list (using the calipers as a guide). I lastly took a depth measurement of the screw hole by inserting the screw, then marking the screw with tape when it was fully inserted. I removed the screw, then measured from the tip to the tape to get the depth. Most of the depth is extra and unused (unless you have a really long screw), but I wanted to get as close to the original design as possible. Modeling Next, it was time to fire up FreeCAD and start a new project. I made a new body, then used Sketcher to add sketches of circles centered on the XY-plane (top view) using the measured diameters (but not the groove one). I gave those sketches helpful names and applied vertical offsets for each of them corresponding to the heights that I also measured. I then began applying Part Design operations to the sketches starting from the bottom. I used combinations of pads and lofts to create the knob's general shape. Note : I needed to add an additional circle with the same diameter as one of them for a separate reference point. I also needed to add a circle at the highest point of the knob for the loft to work. For the groove, I added a sketch on the YZ-plane (side view) of a tiny triangle, then offset it at the approximate height from Z and distance from Y (radius, or half the measured diameter). I applied a “Groove” to that sketch to create the groove by revolving it around the Y-axis. At this point, I had a model that I was already really proud of. I then used some visual comparison with the physical knob to further tweak the dimensions (as well as added fillets to smooth out the very top and the groove) until I got something that more closely resembled it on my screen. At this point, I wasn't going to change anything else until printing out what I'd modeled to compare for real. But I still needed to add one detail… The hole with threading for the screw. Because that was bound to require more than one print to get right. Thread Trouble Before even figuring out how to make the threaded hole, I had to discern what screw I had in order to design with it in mind. I looked up size charts for Metric/Imperial (or Unified Thread Standard, abbreviated “UTS”) screws, took the dimensions of my screw as best I could, and compared it to the charts. It seemed to closest