# CAD for 3DP (Computer Aided Design for 3D Printing) The main CAD program I use is [[FreeCAD]]. ## fitment I have a more extensive spreadsheet in Airtable, but here's a summary of what I've found. These results have been validated by printing, usually with the following parameters: - Material: Prusament PLA - Printer: Prusa Mk3S+ - Detail level: 0.10mm or better NB: I am not a machinist. When I use the words "tight", "close", "loose" etc I have no idea if I'm doing so correctly. I just mean that the fit is "tight" etc in my own experience. parametric screw, nuts, and washers: https://makerworld.com/en/models/1055250#profileId-1042636 ### screw/bolt holes | Nominal | Loose fit | Close fit | Tight fit | Press fit | Tap | | ------- | --------- | --------- | --------- | --------- | ------------------- | | \#6-40 | 0.154 in | 0.144 in | | 0.139 in | 0.103 - 0.108 in | | M2 | | | | 2.6 mm | 1.9 mm is ??? | | M2.5 | | | | | 2.3 mm is too tight | | M3 | | 3.2 mm | | | 2.8 mm is tight | ### Hex Nut holes measurements represent side-to-side, not point-to-point | Nominal | Loose fit | Close fit | Tight fit | Press fit | | ------- | --------- | --------- | --------- | --------- | | \#6-40 | | 0.315 in | 0.312 in | |