Re: [CAD_CAM_EDM_DRO] Re: Does anyone know of some cheap gear designsoftware ?

stevenson_engineers wrote:

>
> > hawk_realm wrote:
> > >
> > > Hi,
> > > Does anyone know of any cheap (or free) CAD gear design software ?
> > > Or maybe a plug-in for 3DSMAX ?
> >

> Doug Fortune wrote:
> > Try this page, it will generate DXF given your gear parameters
> > (you'll need to convert the DXF-> gcode)
> >
> > http://sinfor.lcs.mit.edu:8180/pcbmill/gears
> >
> > cheers
> > Doug Fortune
> > http://www.cncKITS.com


> This page that Doug has linked to will produce a gear for CAD and
> illustration purposes only. It's in no way accurate as regards being
> a true involute. One way to check this is try to draw a gear of 14.5PA
> and a low number of teeth say 12, and look at the result.

Hi again John:

You could be correct as to the accuracy <or lack of...> of the above link,
I don't know.

However regarding a 14.5 PA (pressure angle) gear of 12 teeth,

Machinists handbook 23 (page 1772) says the MINIMUM number of teeth
for these pressure angles should be:

20 degree PA - minimum teeth 18
25 degree PA - minimum teeth 12

By extrapolation then, a 14.5 PA angle gear should have more than 18
teeth (ie a 14.5PA gear of 12 teeth is undefined and so using it for
an example/counterexample is not relevant). In any case, for small
gears you probably want to be hobbing them (a valid cnc operation!),
otherwise the required mill bit dia would be exceedingly small!

Anyway to bring it back 'on topic', I found geargen 1.1 at this site:

http://www.bookcase.com/library/software/msdos . desktop . cad . html

and I'll give it a try as you suggest.

cheers
Doug Fortune
http://www.cncKITS.com