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Posted by mikecb1 on August 4, 2008, 1:03 pm
Please log in for more thread options On Aug 3, 7:14=A0pm, petercolma...@hotmail.com wrote:
>
>
>
>
>
> > I need to make a 12 tooth 20DP 14.5 degree involute spur gear.
>
> > I've cut plenty of low tooth count cycloidal clock gears, but this is
> > the first time I've tried to make an involute gear. =A0I started with a
> > blank (12 + 2)/20 =3D 0.700 inch diameter, and mounted this on a mandre=
l
> > on my dividing head. =A0I then cut 12 teeth 0.108 inch deep with a new
> > No 8 B&S type 14.5 degree involute gear cutter.
>
> > The resulting gear is not satisfactory, and does not mesh properly
> > with other 20 DP gears I have (e.g. the change gears for my Myford
> > lathe). =A0The gear also looks odd compared to my Myford gears, in that
> > instead of having flat-topped teeth, the teeth have sharp points
> > rather like cycloidal clock pinions. =A0It also looks for all the world
> > as if the teeth on my gear would need to be undercut at the bases in
> > order to mesh correctly, but clearly this can't be done with plunge-
> > cutting cutter.
>
> > I'd be most grateful for some advice. =A0The No 8 cutter is supposed to
> > be suitable for gears with 12 or 13 teeth, but looking through some
> > books just now I read that gears with so few teeth do need to be
> > undercut. =A0How is this possible?
>
> > TIA
>
> > Mike
>
> Hi Mike
>
> On the face of it, It sems that you have it all done correctly, I can
> only suppose that you have made an error somewhere.
> Lets go through it all, firstly check the blank OD , if OK then check
> the dividing head, is it set for the right number of teeth, as this
> could lead to the results you have got, Alternatively, have you gone
> deeper than 108",again you an check this on the gear you have cut. If
> all this checks out OK you need to look at the cutter, offer it up to
> a similar cout wheel from the Myford chain and see if it could have
> cut the teeth.
> I am happy to have a look at it all if you get them to me
> Peter- Hide quoted text -
>
> - Show quoted text -
Peter
Thank you for your advice. I went through everything today, and as
you predicted I made a mistake. Somehow I managed to cut the gear too
deeply. Only .010" or so, but enough to ruin the meshing. I've just
cut another gear to the correct depth (in my caution it's actually a
couple of thou under), and it meshes fine with my Myford gears. It
also looks right, with flat tops on the teeth!
Thanks again
Mike
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>
> I've cut plenty of low tooth count cycloidal clock gears, but this is
> the first time I've tried to make an involute gear. =A0I started with a
> blank (12 + 2)/20 =3D 0.700 inch diameter, and mounted this on a mandrel
> on my dividing head. =A0I then cut 12 teeth 0.108 inch deep with a new
> No 8 B&S type 14.5 degree involute gear cutter.
>
> The resulting gear is not satisfactory, and does not mesh properly
> with other 20 DP gears I have (e.g. the change gears for my Myford
> lathe). =A0The gear also looks odd compared to my Myford gears, in that
> instead of having flat-topped teeth, the teeth have sharp points
> rather like cycloidal clock pinions. =A0It also looks for all the world
> as if the teeth on my gear would need to be undercut at the bases in
> order to mesh correctly, but clearly this can't be done with plunge-
> cutting cutter.
>
> I'd be most grateful for some advice. =A0The No 8 cutter is supposed to
> be suitable for gears with 12 or 13 teeth, but looking through some
> books just now I read that gears with so few teeth do need to be
> undercut. =A0How is this possible?
>
> TIA
>
> Mike