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Machining internal gear teeth with a right angle head

SShep71

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Sep 17, 2014
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San Diego, Ca
I have a design I am looking to try to keep in house and I was curious about this possible solution. I have to machine a sun gear with an internal dimension of 10", to a depth of 6", the pitch has yet to be worked out but it will not be fine as there will be three planetary gears rotating around the central axis. Would it be possible to use a right angle head with a formed carbide endmill to do this in my machining center? I did some searching and found that there are a few companies that make "low profile" right angle heads for tight ID work. I want to try to avoid sending the parts out to a gear shop if I can, if I can add a tool like a right angle head and come up with a solution in the long run I feel as if it would pay off. I will still send the design out for a quote but as so many of the shops that used to do this type of work are gone, I can imagine the demand and cost of the machine time would be exceptionally high. I will try to work out a generic solidworks drawing and post a picture here for reference.
 
I have a design I am looking to try to keep in house and I was curious about this possible solution. I have to machine a sun gear with an internal dimension of 10", to a depth of 6", the pitch has yet to be worked out but it will not be fine as there will be three planetary gears rotating around the central axis. Would it be possible to use a right angle head with a formed carbide endmill to do this in my machining center? I did some searching and found that there are a few companies that make "low profile" right angle heads for tight ID work. I want to try to avoid sending the parts out to a gear shop if I can, if I can add a tool like a right angle head and come up with a solution in the long run I feel as if it would pay off. I will still send the design out for a quote but as so many of the shops that used to do this type of work are gone, I can imagine the demand and cost of the machine time would be exceptionally high. I will try to work out a generic solidworks drawing and post a picture here for reference.

A fellows gear shaper might cost less than an angle head and do it much faster.

If this is your own product and you can just leave the shaper set up for this job it might be a smart move. Need a pretty big shaper to do that size part though.
 
Short answer is no unless your gearbox is extremely low quality. Your 6" face with means it will most likely have to go on a 36" Fellows, as most #6 Fellows (the next size down machine) will not stroke 6". You might find a shop with Hydrostroke that could cut it, but I would forget the end mill idea as its simply unrealistic.
 
Makes sense, I was just thinking I could have justified an angle head. I can't find and Fellows that are around me and a decent price. But there are a few shapers around. There was a vertical shaper a little while back on Craigslist, it would take a while to cut the teeth and rotate the shell with a rotary table, but it seems plausible at this point. Still planning on sending it out for quote though.
 
there are a few shapers around.
Shaper != gear shaper. Different animal entirely.

There was a vertical shaper a little while back on Craigslist, it would take a while to cut the teeth and rotate the shell with a rotary table, but it seems plausible at this point.
Do one part, then see if you want to continue down that road ...

With a 6" face, this is not going to be cheap to do. If you think the quotes are high, wait until you see what a 36 Fellows costs. A clapped-out one, even.
 
Hi SShep 71:
Have you considered having this gear wire EDM cut?
It'll be slow and expensive, but that'll be true no matter what process you choose.

If it's just a hacker gear, you could also consider making a custom solution, like a small circular saw mounted on an outrigger with a motorized drive.
The saw blade would be your gear cutter, and the whole thing could drop into the bore of the gear.

I've never seen internal gears cut that way (it's a hack after all) but I have seen big keyways cut that way, somewhere on the internet way back when.
It may have even been here on Practical Machinist.
Here's a pic of a commercial grade gadget made by a company called "Eltool" in Mansfield Ohio that is the right configuration.
Maybe buy one and adapt it?

You are going to need a big rotary table though, and you'll have to block up the part enough to get the cutter past the part without crashing into the rotary.
Your gear will end up being AGMA class "cement mixer gear" too...don't expect to be able to load it too much or run it very fast.
By the time you build the contraption and get the rotary it also will not be cheap, so maybe just bite the bitter pill and outsource it.
I'll betcha you'll get a better, cheaper gear, even if you have to pay Rush Gear prices.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
 

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Shaper != gear shaper. Different animal entirely.
Do one part, then see if you want to continue down that road ...
With a 6" face, this is not going to be cheap to do. If you think the quotes are high, wait until you see what a 36 Fellows costs. A clapped-out one, even.

Presuming that it is not required to be an actually quality gear, ( given the way OP was wanting to do it to begin with ) he could always just buy an old vertical slotter and use a Form Tool. Most all those old girls had/have rotary tables on them already, as part of the machine. That'd be the most economical route. Painfully slow, but economical.


(EDITED TO CORRECT)
 
Usually a vertical stroke shaper (the kind with integrated rotary tables) is referred to as a "slotter".

Not a recommendation, just v trying to clarify because there is already some confusion happening.
 
Presuming that it is not required to be an actually quality gear, ( given the way OP was wanting to do it to begin with ) he could always just buy an old vertical slotter and use a Form Tool. Most all those old girls had/have rotary tables on them already, as part of the machine. That'd be the most economical route. Painfully slow, but economical.


(EDITED TO CORRECT)

Yeah, I have one of those with the inbuilt RT. It's *possible* all right, just like using a conventional shaper can be used to make a rack. Which I have done. Once.

Not if you want a lot and put any value on your time though.

PDW
 
Yeah, I have one of those with the inbuilt RT. It's *possible* all right, just like using a conventional shaper can be used to make a rack. Which I have done. Once.
Not if you want a lot and put any value on your time though.
PDW

Time, schmime. Saving money & keeping it in-house. Those gear shops are making too much money for no real reason. It's not like it takes any real skill or special machinery to make good parts. :rolleyes5: Ameyerite or ameyerite? :stirthepot:
 
I think I would question the design of a planetary gear box where the face width of a 10" id internal gear is 6". Assuming the planets are no bigger than 5" in diameter, that is a pretty wide face width. Of course I don't have all the details- just sayin, that's all, as there may be more to it.
 
Usually a vertical stroke shaper (the kind with integrated rotary tables) is referred to as a "slotter".

Not a recommendation, just v trying to clarify because there is already some confusion happening.

And to pick flyshit from pepper, Pratt and Whitney specifically called their machine a "vertical shaper".
 
"And to pick flyshit from pepper". My college roommate's wife had that very job at a spice company, except all she did was look for it and reject the shipment if there wasn't enough pepper in the flyshit!
 
I spent this past weekend skiing and thinking about how to go about this the most economical way possible (with some efficiency in mind). After thinking about what I actually need the outer shell to do, I found that I can significantly reduce the overall depth of the shell. This reduces the size of the design, cost of materials, and better yet, reducing the design and going with a shallow ring allows me to look toward off the shelf solutions such as a planetary ring gear and mount it to a carrier shell to do what I had hoped to accomplish. Trying to use a vertical slotter "shaper", horizontal shaper, or trying to figure out if a formed endmill on that low profile spindle attachment would have been a fun... >fun?< ...feat to accomplish, but I don't want this to turn into a white-whale project. I want to build this machine, prove it works, then move on.
 








 
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