1. Can anyone help me understand the units for the circular_pitch
parameter in the gear() module as described above?
2. Can anyone see the source of my confusion about the 16DP

Mark, Thanks for the reply. As per the other posts, I think I will be able to do this all in OpenSCAD, and not have to use multiple applications. But it is good to know of those resources. Thanks! Kevin On Sat, Dec 22, 2018 at 1:48 PM Mark Schafer <mschafer@wireframe.biz> wrote: > Hi Kevin, > As others have pointed out Circular pitch means something slightly > different and direct measurement is difficult (also pressure angle).. > > I suggest looking at the links in this reference: > - https://github.com/jnweiger/inkscape-gears-dev > > This plugin will draw gears in Inkscape ( a free OS vector drawing > program). > This might help you to match the gear you have by direct comparison with a > 2D drawing. > You can also export to openSCAD directly but this will only make simple > gears with no 3D profiling but you can use it to learn about these > parameters and make direct 2D comparisons. Then create gears that match in > Greg's library. > > Cheers, Mark... > On 12/23/2018 2:14 AM, Kevin Toppenberg wrote: > > I am trying to model a gear for an Atlas metal lathe. I have some > original (real-life) gears, but want to print one with a different number > of teeth. > > I have found this gear library by GregFrost: > https://www.thingiverse.com/thing:3575/files > I know that this list is not responsible for the library, but it seems to > be a good one, and I am hoping someone here can help. > > My question is about the units of the input parameters. For example, in > the file parametric_involute_gear_v5.0.scad there are some example gears. > I modified one slightly as follows: > > gear (number_of_teeth=64, > circular_pitch=285.0, > circles=0); > > I chose the value for circular_pitch experimentally. First I put an > Echo() statement in the gear_shape module such that it reports the minor > diameter, pitch diameter, and major diameter (in mm). I then slowly > modified the circular_pitch value until it matched the measurements of my > actual real-life gear, taken with my micrometer. > > I am confused about what circular_pitch is supposed to represent. I > reviewed standard gear terms from here: > https://en.wikipedia.org/wiki/List_of_gear_nomenclature#Circular_Pitch > Circular pitch should be the distance (in mm) from tooth to tooth. In my > actual real-life gear, the value is about 5 mm. > > On a slightly different tact, I am also confused about gear terminology > used for my lathe. The gears are typically described using inches and > diametral pitch (which is supposed to be 1/circular_pitch). According to > this site: > https://www.practicalmachinist.com/vb/general/need-atlas-lathe-gear-208658/ > (which references here: http://www.lathes.co.uk/atlas/), Atlas gears use > a 16DP, which I think means 16 diametral pitch or 16 teeth per inch. I'm > not sure I believe this number, because my real-life gear with 20 teeth has > a diameter of 1.475 inches, circumference of ~4.3 inches, and thus 20/4.3 = > ~4.6 teeth/inch. > > Summary: > > 1. Can anyone help me understand the units for the circular_pitch > parameter in the gear() module as described above? > 2. Can anyone see the source of my confusion about the 16DP > > > Thanks in advance, > Kevin T > > _______________________________________________ > OpenSCAD mailing listDiscuss@lists.openscad.orghttp://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 >

kdtop wrote > Instead, lathes have a secondary > drive rod that moves the carriage along slowly, and these can be plastic. > In fact many of the smaller bench-top lathes use plastic gears for this. I have a metal lathe on my own and know exactly what you want ... and what forces are involved. However, plastic gears and 3D printed gears are not the same. At least you should use PETG or Nylon. ABS and PLA will not do the job (for long) as a 1.75 module is not very strong. You can't use normal grease lube for plastic gears. Rather use silicone grease. But try, and have fun. -- Sent from: http://forum.openscad.org/

Parkinbot, Fingers crossed that they don't break soon! I have nylon (Taulman 680, I think) and can print them in that if they do. Thanks again Kevin On Sun, Dec 23, 2018 at 7:03 AM Parkinbot <rudolf@digitaldocument.de> wrote: > kdtop wrote > > Instead, lathes have a secondary > > drive rod that moves the carriage along slowly, and these can be plastic. > > In fact many of the smaller bench-top lathes use plastic gears for this. > > I have a metal lathe on my own and know exactly what you want ... and what > forces are involved. However, plastic gears and 3D printed gears are not > the > same. At least you should use PETG or Nylon. ABS and PLA will not do the > job > (for long) as a 1.75 module is not very strong. You can't use normal grease > lube for plastic gears. Rather use silicone grease. > But try, and have fun. > > > > > > > -- > Sent from: http://forum.openscad.org/ > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >