Hi, Now that I have undertaken to design my own 3D models, rather than use other folks work, I understand that there is much I will have to learn. As part of that learning I need some basic info. When a machinist wishes to drill a hole for an M3 machine screw to pass through there are many places where he can look for that information and he will find that there are suggested hole sizes for a "close fit", a "normal fit" and a "loose fit". Likewise if he needs to drill a hole for tapping for that M3 machine screw he will find that there are suggested hole sizes for 50% threads and 75% threads. So my question is when working with different kinds of 3D printing technologies and materials used in those type of machines are there places I can go to find that same kind of information? As a simple test I used the dimensions I would use for aluminum to create a test part over at Shapeways using their "Versatile Plastic" material which has proven, using other folks designs, to be very good for the type of parts I have been making. As I expected the holes were too bit too small although the linear dimensions were quite good. So if anyone has this knowledge or links to this knowledge I would be most appreciative. Thanks. Frederick -- Sent from: http://forum.openscad.org/

On 23 July 2018 at 08:37, fcwilt <fcwilt@embarqmail.com> wrote: > Hi, > > Now that I have undertaken to design my own 3D models, rather than use other > folks work, I understand that there is much I will have to learn. > > As part of that learning I need some basic info. > > When a machinist wishes to drill a hole for an M3 machine screw to pass > through there are many places where he can look for that information and he > will find that there are suggested hole sizes for a "close fit", a "normal > fit" and a "loose fit". > > Likewise if he needs to drill a hole for tapping for that M3 machine screw > he will find that there are suggested hole sizes for 50% threads and 75% > threads. > > > So my question is when working with different kinds of 3D printing > technologies and materials used in those type of machines are there places I > can go to find that same kind of information? > > > As a simple test I used the dimensions I would use for aluminum to create a > test part over at Shapeways using their "Versatile Plastic" material which > has proven, using other folks designs, to be very good for the type of parts > I have been making. > > As I expected the holes were too bit too small although the linear > dimensions were quite good. > > > So if anyone has this knowledge or links to this knowledge I would be most > appreciative. 3DHubs have an article and infographic about designing for different manufacturing methods, including FDM printing: https://www.3dhubs.com/knowledge-base/key-design-considerations-3d-printing Different printers and materials and slicers and tuning produce different results, especially at the lower end of the market where machines and filament vary, or where people do not take the time to properly learn how FDM printing works and tune correctly. You can print test parts to see how your machine and settings fare, the Maker's Muse tolerance test is one such method: https://www.youtube.com/watch?v=TYuLVN3YHw8 Specifically for metric screw holes, I made this calibration plate: https://www.thingiverse.com/thing:2221050 Jamie

You want the target hole size to be the same as for machining. If the Shapeways process is accurate then you have to consider the fact that STL files only have faceted holes. I.e. a round hole will end up polygonal, with its vertices on the circle. That means the sides of the polygon will be inside the circle and thus the hole is too small. You need to increase the radius by dividing by cos(180 / n) where n is the number of sides. On 22 July 2018 at 23:37, fcwilt <fcwilt@embarqmail.com> wrote: > Hi, > > Now that I have undertaken to design my own 3D models, rather than use > other > folks work, I understand that there is much I will have to learn. > > As part of that learning I need some basic info. > > When a machinist wishes to drill a hole for an M3 machine screw to pass > through there are many places where he can look for that information and he > will find that there are suggested hole sizes for a "close fit", a "normal > fit" and a "loose fit". > > Likewise if he needs to drill a hole for tapping for that M3 machine screw > he will find that there are suggested hole sizes for 50% threads and 75% > threads. > > > So my question is when working with different kinds of 3D printing > technologies and materials used in those type of machines are there places > I > can go to find that same kind of information? > > > As a simple test I used the dimensions I would use for aluminum to create a > test part over at Shapeways using their "Versatile Plastic" material which > has proven, using other folks designs, to be very good for the type of > parts > I have been making. > > As I expected the holes were too bit too small although the linear > dimensions were quite good. > > > So if anyone has this knowledge or links to this knowledge I would be most > appreciative. > > Thanks. > > Frederick > > > > -- > Sent from: http://forum.openscad.org/ > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/undersized_circular_objects I use cylinder_outer() so much I made my own library for it: https://github.com/superjamie/handyscad Jamie On 23 July 2018 at 08:57, nop head <nop.head@gmail.com> wrote: > You want the target hole size to be the same as for machining. If the > Shapeways process is accurate then you have to consider the fact that STL > files only have faceted holes. I.e. a round hole will end up polygonal, with > its vertices on the circle. That means the sides of the polygon will be > inside the circle and thus the hole is too small. You need to increase the > radius by dividing by cos(180 / n) where n is the number of sides. > > > > On 22 July 2018 at 23:37, fcwilt <fcwilt@embarqmail.com> wrote: >> >> Hi, >> >> Now that I have undertaken to design my own 3D models, rather than use >> other >> folks work, I understand that there is much I will have to learn. >> >> As part of that learning I need some basic info. >> >> When a machinist wishes to drill a hole for an M3 machine screw to pass >> through there are many places where he can look for that information and >> he >> will find that there are suggested hole sizes for a "close fit", a "normal >> fit" and a "loose fit". >> >> Likewise if he needs to drill a hole for tapping for that M3 machine screw >> he will find that there are suggested hole sizes for 50% threads and 75% >> threads. >> >> >> So my question is when working with different kinds of 3D printing >> technologies and materials used in those type of machines are there places >> I >> can go to find that same kind of information? >> >> >> As a simple test I used the dimensions I would use for aluminum to create >> a >> test part over at Shapeways using their "Versatile Plastic" material which >> has proven, using other folks designs, to be very good for the type of >> parts >> I have been making. >> >> As I expected the holes were too bit too small although the linear >> dimensions were quite good. >> >> >> So if anyone has this knowledge or links to this knowledge I would be most >> appreciative. >> >> Thanks. >> >> Frederick >> >> >> >> -- >> Sent from: http://forum.openscad.org/ >> >> _______________________________________________ >> OpenSCAD mailing list >> Discuss@lists.openscad.org >> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org > > > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

I think what you maybe referring to is the topic of “engineering fit”… here’s a link to the wikipedia article on it… https://en.wikipedia.org/wiki/Engineering_fit My personal experience is that with an FDM printer you don’t have anything close to the accuracy, repeatability and precision needed to achieve anything but the most coarse levels of engineering fit… but then again, if you have parts that fit in other parts you have to start somewhere. I think you may find the following wikipedia page particularly useful in explaining the components that are involved in machining and when you consider the inconsistencies of filament flow, temperature regulation, extruder positioning etc.you can appreciate that there’s no simple fix. https://en.wikipedia.org/wiki/Accuracy_and_precision Anyway, I hope you find the link as useful as I did. > On Jul 22, 2018, at 4:26 PM, Jamie Bainbridge <jamie.bainbridge@gmail.com> wrote: > > https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/undersized_circular_objects > > I use cylinder_outer() so much I made my own library for it: > > https://github.com/superjamie/handyscad > > Jamie > > > On 23 July 2018 at 08:57, nop head <nop.head@gmail.com> wrote: >> You want the target hole size to be the same as for machining. If the >> Shapeways process is accurate then you have to consider the fact that STL >> files only have faceted holes. I.e. a round hole will end up polygonal, with >> its vertices on the circle. That means the sides of the polygon will be >> inside the circle and thus the hole is too small. You need to increase the >> radius by dividing by cos(180 / n) where n is the number of sides. >> >> >> >> On 22 July 2018 at 23:37, fcwilt <fcwilt@embarqmail.com> wrote: >>> >>> Hi, >>> >>> Now that I have undertaken to design my own 3D models, rather than use >>> other >>> folks work, I understand that there is much I will have to learn. >>> >>> As part of that learning I need some basic info. >>> >>> When a machinist wishes to drill a hole for an M3 machine screw to pass >>> through there are many places where he can look for that information and >>> he >>> will find that there are suggested hole sizes for a "close fit", a "normal >>> fit" and a "loose fit". >>> >>> Likewise if he needs to drill a hole for tapping for that M3 machine screw >>> he will find that there are suggested hole sizes for 50% threads and 75% >>> threads. >>> >>> >>> So my question is when working with different kinds of 3D printing >>> technologies and materials used in those type of machines are there places >>> I >>> can go to find that same kind of information? >>> >>> >>> As a simple test I used the dimensions I would use for aluminum to create >>> a >>> test part over at Shapeways using their "Versatile Plastic" material which >>> has proven, using other folks designs, to be very good for the type of >>> parts >>> I have been making. >>> >>> As I expected the holes were too bit too small although the linear >>> dimensions were quite good. >>> >>> >>> So if anyone has this knowledge or links to this knowledge I would be most >>> appreciative. >>> >>> Thanks. >>> >>> Frederick >>> >>> >>> >>> -- >>> Sent from: http://forum.openscad.org/ >>> >>> _______________________________________________ >>> OpenSCAD mailing list >>> Discuss@lists.openscad.org >>> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >> >> >> >> _______________________________________________ >> OpenSCAD mailing list >> Discuss@lists.openscad.org >> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >> > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org

And pragmatically - your extruder will ooze a little based on temp, layer height, and viscosity of the specific filament. So in practise even if you manually account for inside holes vs outside holes (your stl will not know) then you need to test your own equipment and filament to work out the final fiddle factor to make it fit well. Or drill it out :) (if its small) On 7/23/2018 12:09 PM, Hugo Jackson wrote: > I think what you maybe referring to is the topic of “engineering fit”… here’s a link to the wikipedia article on it… > > https://en.wikipedia.org/wiki/Engineering_fit > > My personal experience is that with an FDM printer you don’t have anything close to the accuracy, repeatability and precision needed to achieve anything but the most coarse levels of engineering fit… but then again, if you have parts that fit in other parts you have to start somewhere. > > I think you may find the following wikipedia page particularly useful in explaining the components that are involved in machining and when you consider the inconsistencies of filament flow, temperature regulation, extruder positioning etc.you can appreciate that there’s no simple fix. > > https://en.wikipedia.org/wiki/Accuracy_and_precision > > Anyway, I hope you find the link as useful as I did. > >> On Jul 22, 2018, at 4:26 PM, Jamie Bainbridge <jamie.bainbridge@gmail.com> wrote: >> >> https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/undersized_circular_objects >> >> I use cylinder_outer() so much I made my own library for it: >> >> https://github.com/superjamie/handyscad >> >> Jamie >> >> >> On 23 July 2018 at 08:57, nop head <nop.head@gmail.com> wrote: >>> You want the target hole size to be the same as for machining. If the >>> Shapeways process is accurate then you have to consider the fact that STL >>> files only have faceted holes. I.e. a round hole will end up polygonal, with >>> its vertices on the circle. That means the sides of the polygon will be >>> inside the circle and thus the hole is too small. You need to increase the >>> radius by dividing by cos(180 / n) where n is the number of sides. >>> >>> >>> >>> On 22 July 2018 at 23:37, fcwilt <fcwilt@embarqmail.com> wrote: >>>> Hi, >>>> >>>> Now that I have undertaken to design my own 3D models, rather than use >>>> other >>>> folks work, I understand that there is much I will have to learn. >>>> >>>> As part of that learning I need some basic info. >>>> >>>> When a machinist wishes to drill a hole for an M3 machine screw to pass >>>> through there are many places where he can look for that information and >>>> he >>>> will find that there are suggested hole sizes for a "close fit", a "normal >>>> fit" and a "loose fit". >>>> >>>> Likewise if he needs to drill a hole for tapping for that M3 machine screw >>>> he will find that there are suggested hole sizes for 50% threads and 75% >>>> threads. >>>> >>>> >>>> So my question is when working with different kinds of 3D printing >>>> technologies and materials used in those type of machines are there places >>>> I >>>> can go to find that same kind of information? >>>> >>>> >>>> As a simple test I used the dimensions I would use for aluminum to create >>>> a >>>> test part over at Shapeways using their "Versatile Plastic" material which >>>> has proven, using other folks designs, to be very good for the type of >>>> parts >>>> I have been making. >>>> >>>> As I expected the holes were too bit too small although the linear >>>> dimensions were quite good. >>>> >>>> >>>> So if anyone has this knowledge or links to this knowledge I would be most >>>> appreciative. >>>> >>>> Thanks. >>>> >>>> Frederick >>>> >>>> >>>> >>>> -- >>>> Sent from: http://forum.openscad.org/ >>>> >>>> _______________________________________________ >>>> OpenSCAD mailing list >>>> Discuss@lists.openscad.org >>>> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >>> >>> >>> _______________________________________________ >>> OpenSCAD mailing list >>> Discuss@lists.openscad.org >>> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >>> >> _______________________________________________ >> OpenSCAD mailing list >> Discuss@lists.openscad.org >> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org

https://makezine.com/2015/07/22/tips-3d-printing-press-fit-parts/ It's not exactly what you were asking about, but I found this article to have some interesting tips on building press-fit parts, and in particular on making pegs that go into holes. The conclusion in a nutshell:  don't try to put round pegs into round holes.  The tolerances are too tight and the processes too inexact.  Instead, put hollow octagonal pegs into round holes, so that the pegs and the holes can deform a little as they're pressed together.

Thanks to everyone for the wealth of information. Many good ideas and much to read. Frederick -- Sent from: http://forum.openscad.org/

Jamie Bainbridge wrote > Specifically for metric screw holes, I made this calibration plate: > https://www.thingiverse.com/thing:2221050 > > Jamie That seems to me like a very good idea. I will have to have one printed up for me. Frederick -- Sent from: http://forum.openscad.org/

Hi folks, This is of interest to me as well. I have successfully threaded quite a few holes in 3-D models and found it very satisfactory. Choosing the right hole though is somewhat hit or miss for me, and I will print Hugo's plate with different holes as a better indication of what my own printer (at its settings) makes holes. I am also going to try these "M3 x 3mm Solid Brass Cylinder Knurled Threaded Round Insert Embedded Nuts" (search eBay?) as an alternative as well.  I am hoping to slip them on my soldering iron tip and insert/melt them into my models.  Hugo's plate with the graded holes will help here as well. Rob On 23/07/18 10:27, Mark Schafer wrote: > And pragmatically - your extruder will ooze a little based on temp, > layer height, and viscosity of the specific filament. > So in practise even if you manually account for inside holes vs > outside holes (your stl will not know) then you need to test your own > equipment and filament to work out the final fiddle factor to make it > fit well. > > Or drill it out :) (if its small) > > > On 7/23/2018 12:09 PM, Hugo Jackson wrote: >> I think what you maybe referring to is the topic of “engineering >> fit”… here’s a link to the wikipedia article on it… >> >> https://en.wikipedia.org/wiki/Engineering_fit >> >> My personal experience is that with an FDM printer you don’t have >> anything close to the accuracy, repeatability and precision needed to >> achieve anything but the most coarse levels of engineering fit… but >> then again, if you have parts that fit in other parts you have to >> start somewhere. >> >> I think you may find the following wikipedia page particularly useful >> in explaining the components that are involved in machining and when >> you consider the inconsistencies of filament flow, temperature >> regulation, extruder positioning etc.you can appreciate that there’s >> no simple fix. >> >> https://en.wikipedia.org/wiki/Accuracy_and_precision >> >> Anyway, I hope you find the link as useful as I did. >> >>> On Jul 22, 2018, at 4:26 PM, Jamie Bainbridge >>> <jamie.bainbridge@gmail.com> wrote: >>> >>> https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/undersized_circular_objects >>> >>> >>> I use cylinder_outer() so much I made my own library for it: >>> >>> https://github.com/superjamie/handyscad >>> >>> Jamie >>> >>> >>> On 23 July 2018 at 08:57, nop head <nop.head@gmail.com> wrote: >>>> You want the target hole size to be the same as for machining. If the >>>> Shapeways process is accurate then you have to consider the fact >>>> that STL >>>> files only have faceted holes. I.e. a round hole will end up >>>> polygonal, with >>>> its vertices on the circle. That means the sides of the polygon >>>> will be >>>> inside the circle and thus the hole is too small. You need to >>>> increase the >>>> radius by dividing by cos(180 / n) where n is the number of sides. >>>> >>>> >>>> >>>> On 22 July 2018 at 23:37, fcwilt <fcwilt@embarqmail.com> wrote: >>>>> Hi, >>>>> >>>>> Now that I have undertaken to design my own 3D models, rather than >>>>> use >>>>> other >>>>> folks work, I understand that there is much I will have to learn. >>>>> >>>>> As part of that learning I need some basic info. >>>>> >>>>> When a machinist wishes to drill a hole for an M3 machine screw to >>>>> pass >>>>> through there are many places where he can look for that >>>>> information and >>>>> he >>>>> will find that there are suggested hole sizes for a "close fit", a >>>>> "normal >>>>> fit" and a "loose fit". >>>>> >>>>> Likewise if he needs to drill a hole for tapping for that M3 >>>>> machine screw >>>>> he will find that there are suggested hole sizes for 50% threads >>>>> and 75% >>>>> threads. >>>>> >>>>> >>>>> So my question is when working with different kinds of 3D printing >>>>> technologies and materials used in those type of machines are >>>>> there places >>>>> I >>>>> can go to find that same kind of information? >>>>> >>>>> >>>>> As a simple test I used the dimensions I would use for aluminum to >>>>> create >>>>> a >>>>> test part over at Shapeways using their "Versatile Plastic" >>>>> material which >>>>> has proven, using other folks designs, to be very good for the >>>>> type of >>>>> parts >>>>> I have been making. >>>>> >>>>> As I expected the holes were too bit too small although the linear >>>>> dimensions were quite good. >>>>> >>>>> >>>>> So if anyone has this knowledge or links to this knowledge I would >>>>> be most >>>>> appreciative. >>>>> >>>>> Thanks. >>>>> >>>>> Frederick >>>>> >>>>> >>>>> >>>>> -- >>>>> Sent from: http://forum.openscad.org/ >>>>> >>>>> _______________________________________________ >>>>> OpenSCAD mailing list >>>>> Discuss@lists.openscad.org >>>>> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >>>> >>>> >>>> _______________________________________________ >>>> OpenSCAD mailing list >>>> Discuss@lists.openscad.org >>>> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >>>> >>> _______________________________________________ >>> OpenSCAD mailing list >>> Discuss@lists.openscad.org >>> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >> >> _______________________________________________ >> OpenSCAD mailing list >> Discuss@lists.openscad.org >> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org > > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org