Cutting a planetary gear...

[WilliamD]

I understand for the most part about cutting gears. Also realize there's a ton to know about it. I was wondering how you would cut the outside part of a planetary gear setup. The only think I could think of was EDM. Is that how it's done? I wouldn't imagine this would work with a helical gear setup. Just looking for some ideas.

[JH-Q]

I think most of the small commercial planetary gear rings are made by sintering them. ( http://en.wikipedia.org/wiki/Sintering )
And the bigger ones are made with shaper-style machines which use a tool bit to "broach" the form for one teeth and then rotate the workpiece to broach the next teeth. Helical ring gears could be made with EDM which can rotate the electrode or workpiece?

[RICHARD ZASTROW]

WilliamD Do you refer to the internal teeth of the outer ring? If so, you can "broach" them with an appropriately shaped tool in a Bridgeport slotting head attachment and the workpiece on a rotary table. Otherwise, have it machined on a gearshaper like Gleason, Pfauter etc. etc.

[peter@slater]

Rotary Broaching can be used to machine internal and external gear teeth, but it does have some size limitations. This type of broaching is usually for diameters less than 1". The Slater tools shown in the photo can be used on any type CNC or drill type machine.

[WilliamD]

Thank you all for the replies! That certainly clears the issue up. I can't believe I hadn't thought of broaching. But, seems a little more complicated for a project than I'm after right now. Thanks again!

[Adobe Machine]

The Slater System Tools are some of the worlds best, no doubt...Just wish all of us Hobby Guys could afford them..Maybe you have some verbage for our wives " as in gotta have ?" Unfortunatley I have used just about all of my "gotta haves ", need new words ! !

Adobe (old as dirt )

[handlewanker]

Hi WiliamD, you could try a boring bar in the lathe and use the saddle traverse to plunge the boring bar in and out like a shaper one tooth at a time.
I've cut many internal splines like this and a whole lot of keyways for one off jobs.
Getting the single point toolbit to the profile of the internal tooth shape will be your only problem.
If you've got access to a shadograph machine then it's a piece of cake, otherwise a 10X eyepiece magnifier will also do the trick.
Just on the subject of a shadowgraph machine for projecting tool profiles, a friend of mine had to do a similar job cutting the ring gears for a planetary set and we used a canabalised single shot 35mm slide projector to enlarge the image of the tool and projected it onto a white wall panel about 15ft away.
The image was calibrated by projecting a 1/8" diam drill shank and marking a scale on the white panel. I think we got about 50:1 magnification.
The ring gear was cut by racking the lathe saddle with a boring bar.
A gear mounted on the end of the lathe spindle was used to divide the gear teeth up, with the chuck prevented from turning during cuts with a small jack and a piece of wood.
Ian.

[peter@slater]

Originally Posted by Adobe Machine The Slater System Tools are some of the worlds best, no doubt...Just wish all of us Hobby Guys could afford them..Maybe you have some verbage for our wives " as in gotta have ?" Unfortunatley I have used just about all of my "gotta haves ", need new words ! ! Adobe (old as dirt )

I've seen used $1000 Slater holders go for $250 on ebay. Then all you're gonna have to get is a broach. Sometimes those used broach holders just need some new bearings and they're good to go.

[handlewanker]

Hi Adobe, only problem in using a dedicated tool such as this is the actual cutter to produce the work.
I don't know if you could buy a broach off of the shelf unless it was a standard item, but for a custom made one it would probably cost more than the job was worth.
If the job was a production item then the cost is justified by the volume and time it saves.
Ian.

[RICHARD ZASTROW]

WilliamD
I just saw some neat broach stuff at P.H.Horn A DIY type guy could possibly purchase the broach tooling then make or have made the actual cutting insert. If Horn makes the inserts, the min. order is 10 pc.

[joecnc2006]

Anyone have a good gear program, to design it then create a dwg file?

you specify the parameters.

[RICHARD ZASTROW]

joe2000che,
My clumsy method is to construct one tooth with a locating point on the pitch circle where a vertical line from center of the circle intersects the pitch circle itself. Then form a polar array of equal number of teeth your gear requires on the pitch circle. If the teeth are not located correct radially, rotate the array.