On 4 Jan 2016, at 06:16, Gregg Eshelman wrote: > On 1/3/2016 10:37 AM, Kirk Wallace wrote: > >> I have been looking at clock gearing off and on for a while. So far, I >> have found that clock tooth forms are cycloidal, but not really. It >> seems there is a British standard which is based on the ideal cycloidal >> form but uses a circular arc for the curved part of a tooth, rather than >> a cycloid, and clearance is added according to practical experience. I >> haven't been able to find the contents of the standard, but I'm still >> looking. My plan was to use a very small diameter (.015") end mill as a >> universal gear cutting tool for thin wheels from sheet brass. The wheel >> can be drawn in CAD, converted to g-code then cut in XY without using a >> rotary axis. I would appreciate any links or information that could get >> me closer to actually cutting wheels and pinions. Although, pinions are >> a different kettle of fish. > > One way to do it is design the gear in a 2D CAD program then export it > to DXF to import into a CAM program to convert to G-code. > > The free emachineshop software has a gear wizard but it only does > Diametral Pitch. However it allows for arbitrary input in the DP slot so > with a calculator like this > http://www.technobotsonline.com/gear-size-calculator.html you get the > equivalent number to enter. An issue with it is it creates tooth > profiles as a lot of short, straight segments. > > HEEKS CAD/CAM has a gear generating wizard that only does metric gears > so to cut a DP gear you have to convert the other way from emachineshop. > HEEKS' gear wizard uses curves for the teeth and its output is > adjustable after creation. Select the shape and change the numbers. > HEEKS costs $10 for the full version, but the only difference is the > paid version doesn't put a demo notice in the G-Code output. That can > simply be deleted with any text editor. > > FreeCAD's gear wizard is also metric only. > http://www.freecadweb.org/wiki/index.php?title=PartDesign_InvoluteGear > IIRC I couldn't get an exported file from it that would import into HEEKS. >
What about Gearotic? Not free, of course, but might be useful nevertheless. Marcus > Why I got into this was a need to repair a 14 DP gear on one end of a > spool gear in the reverse drive on a 1943 LeBlond Regal 13" 'trainer' > model metal lathe. Most of the gears in its headstock are only 5/16" thick. > > Welded up all the teeth on the chewed up gear, put a pointed rod into a > collet in my PLM2000 mill to center the gear under the spindle, clamped > it down and set the origin to center. Then I fed it the G-code from > HEEKS to make a lot of shallow passes with the largest endmills I had > that were still smaller than the smallest radius in the tooth gullets. I > made different G-code for different mill diameters. > > Ended up going over much of the depth repeatedly, broke all the little > mills I had, despite using cutting oil, but the job got done. > > Other than finding someone with a shaper and either an old 14 pitch > tooth cutter or the skill to grind one, or a hobber with an extra small > diameter 14 pitch hob, it was the only way to fix it. The other gear on > the spool was too close to use normal involute cutters or hobs. > > LeBlond quoted me $1500 and at least three weeks before they could think > about making a new gear. (Probably would have to locate a retired > machinist to come in to do the job!) > > --- > This email has been checked for viruses by Avast antivirus software. > https://www.avast.com/antivirus > > > ------------------------------------------------------------------------------ > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
