gear cutters

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Snag

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Jan 12, 2022, 9:41:26 PMJan 12
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I want to cut some gears for my lathe , the back gear set has some
missing teeth . 14dp gear cutters are hard to find ! Is this one meant
to cut bevel gears , or is it a reference to the cutter geometry ?

https://www.ebay.com/itm/400847658009?

I guess I always have the option of grinding a single point tool to do
the job if I have to . If I go that route I'll probably try building up
the broken teeth with some nickel TIG alloy (Invar42). Those gears have
been soaking in oil for 70 years now , which may make that problematic .
I also have some phosphor bronze filler if that might be a better match .
--
Snag
Let's Go Brandon !

Jim Wilkins

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Jan 13, 2022, 7:07:08 AMJan 13
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"Snag" wrote in message news:sro3gg$r94$1...@dont-email.me...
----------------------
https://pdfcookie.com/download/workshop-practice-series-volume-17-gears-and-gear-cutting-ivan-lawpdf-j9lgooxqqm2o

Law's book describes a simplified method for grinding a cutter with circular
instead of involute curves. For another use I ground a concave circular
cutting edge on a lathe bit with a conical stone in a die grinder.

I made two gear cutters using a jig that aligns the lathe bit radial and
centered on the tooth gap, and repeatedly grinding down the visible contact
spots. It worked, but not particularly well because bluing wouldn't stick to
the smooth hard surface. I didn't think to try candle smoke. Both were
oddballs, one a 30 degree ANSI spline hydraulic pump shaft and the other the
cast iron steering sector on a Roper tractor.

I used the closest-fitting commercial gear cutter I have to rough out the
gaps in the blank, because cutting with a single flycutter bit is very slow
and wears the tool. You could rough out the gaps with the partly formed bit
and finish them after grinding it correctly.

Snag

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Jan 13, 2022, 8:06:23 AMJan 13
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I've got the book ... and I have ground form tools to recut splines
which are much smaller than these 14dp gear teeth . I even built a
holder to go in my boring head for just this use . Just takes time , a
strong light , and a magnifying glass . If you want to smoke something
fire up the OA torch ... and I've seen photos of your sector gear and
remember you had a bit of a glitch starting out . If I do it this way
I'll for sure only cut what I have to , while the noise is annoying the
back gears do work - and it's not like I do this every day .

Bob La Londe

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Jan 13, 2022, 10:42:30 AMJan 13
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I would think for a for a single job a single point might be better than
buying gear cutters. You can grind it to an exact profile rather than
the compromise range of a typical wheel cuter, of course it doesn't
really need to be perfect. Almost no gears are.

I found gear cutter sets on one of the China direct sites like Bang Good
were pretty cheap, but I never bought any. I have pretty much quit
buying from those sites. Most any import item I need is usually on Ebay
where my financial info is better shielded for a few dollars more. I
have some gear cutters I bought as a lot (new very old stock), but it
turned out they are almost all the same cutter. Someday I'll get around
to listing them on Fleabay.

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Snag

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Jan 13, 2022, 8:58:12 PMJan 13
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Looking at the lathe today , I'm onlty missing 2 teeth , Those don't
rise to the effort of grinding a cutter . I'll pull the gears out and
probably use some brass or bronze to build up the missing teeth . Cut to
profile with files and dremel burrs . I was thinking it was more ,
forgot that I have replaced the bull gear - old one was missing like 2
and a half teeth . Won't be tomorrow though . Tomorrow I gotta bake
bread and maybe go to town for some more country style ribs . The ones I
picked up today - a buck fifteen a pound! - were awesome !

Bob La Londe

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Jan 14, 2022, 10:12:30 AMJan 14
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On 1/13/2022 6:58 PM, Snag wrote:

>
>   Looking at the lathe today , I'm onlty missing 2 teeth , Those don't
> rise to the effort of grinding a cutter . I'll pull the gears out and
> probably use some brass or bronze to build up the missing teeth . Cut to
> profile with files and dremel burrs . I was thinking it was more ,
> forgot that I have replaced the bull gear - old one was missing like 2
> and a half teeth . Won't be tomorrow though . Tomorrow I gotta bake
> bread and maybe go to town for some more country style ribs . The ones I
> picked up today - a buck fifteen a pound! - were awesome !

Glad you don't have such an involved project. I did run across
something this morning that might suit you though. I haven't finished
watching it, but I instantly thought of you when it popped up on my feed
while I was having my morning coffee.

Cut any gear with just a slitting saw
https://youtu.be/eC-OctJoWv4

Some folks watch the news or read the paper with their morning coffee.
I watch machining videos on the big screen.

Bob La Londe

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Jan 14, 2022, 10:38:39 AMJan 14
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Part way into the video as he marks out his work I had to smile. I am
reminded that I have first handle knowledge of this. If you spin up a
Sharpie marker it has a very finite RPM limit. At some speed well below
24000 RPM it will explode.


I was thinking this would be tedious and annoying to make a gear this
way, but I do have a 4th axis rotab for the Tormach CNC mill. Then I am
reminded if I had the geometry of the gear all figured out anyway I'd
probably CNC cut it out of flat bar with some clearance reliefs in the
bottom of cut. Either way, let the machine do the work while I go
program something else.
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