I make most gears out of 1/4 inch acetal, sometimes polycarbonate just
because it is easy to get
I use successfully smaller diameter bits to refine the profile
I have never bought gears so I do not know how my gears would mesh with them
I can generate external or internal gears with a shifted profile
Quoting andy pugh <[email protected]>:
On 15 December 2017 at 01:28, <[email protected]> wrote:
I make plastic gears on a table top cnc mill
Just things for toys and do-dads
The reason I asked is that external gears are easy to make, but
internal ones are not.
I make gears for fun, here is a triple coaxial differential gear:
https://photos.app.goo.gl/XaCm1X9HFRKH8fgt1
But I use the hobbing method of gear making, and that can't be used
for internal gears.
To make internal gears you need a Fellows-style gear shaper
https://www.youtube.com/watch?v=UNenwSSZfYU
(Which would be a fun modification to a slotting head on a milling machine)
If you look at stock internal gears:
http://www.hpcgears.com/pdf_c33/17.7.pdf
You will find that getting a pair that differ by only one tooth isn't
that easy. And they will differ in PCD. The PCD difference isn't to
hard too deal with in external gears if you can make them big enough
for the corrections not to distort the teeth too much, but it would be
much easier to not have two PCDs on the planets.
So, you would ideally be making your own internal gears.
I guess it would be possible to single-tooth shape the internal gears:
https://www.youtube.com/watch?v=W69m2cDaqvY
(Or maybe not, my visualisation skills are letting me down there)
--
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916
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