wrote in message
...
On Sat, 21 Jan 2017 13:53:29 -0500, Bob Engelhardt
wrote:

I have a Jet 1024 lathe with a QC gear box. The box has a broken
gear
that is really oddball in that its dimensions are inconsistent with
published standards. Such that I cannot find a replacement in any
of
the usual places.

Anyhow, I intend to make a new gear on my horizontal mill and will
have
to buy a gear cutter. That means that I need to know the pressure
angle. I found a website with a procedure to do that, but it
requires
CAD and before I get into that, I'm trying here.
(http://mikesworkshop.weebly.com/chan...ure-angle.html)

Here is a photo of a couple of teeth on my gear and profiles of the
same
DP from Boston Gear. The Boston Gear profiles are a different
diameter,
so I can't compare by overlaying. I can't tell which angle is
closest
to mine. Anybody know gears well enough to tell?

http://imgur.com/a/7O4O3

Thanks,
Bob

BTW - the lathe is from 1980 or so - if that helps.
I assume you tried Jet already to see if a new gear is available and
found out it is not. Since you are only making one gear you could
grind a fly cutter to fit the existing gear. I have done this and it
works well if only one gear is being made. ....
Eric

I cut two satisfactory (not perfect) gears with flycutter bits too.

The job required a jig that guided the bit blank into centered
alignment with the tooth space. Bluing didn't transfer or print well
on the smooth hardened lathe bit so I held the bit and old gear up to
the light to see the contact and marked the blank's top surface to
show where to grind.

Roughing out the tooth spaces first with a more efficient cutter
helped a lot. The tooth spaces can be cut nearly to size before the
bit has been ground to final fit so it will be freshly sharp for the
finish cut.

The grinding jig might serve as a gauge for depth of cut.

-jsw