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Unread 03-02-2009, 20:30
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Re: FP Gearbox: Last stage gear?

Well, I gave it another shot, and the best I could measure the very last gear (38 teeth, with the extended plastic) is 2.25 module, 20 degrees pressure angle (nearly perfect match). The 12 tooth gear, the one I was interested in, does not appear to be the same, by a good margin, which is obviously very weird.

Since I'm not a gear expert, not even a mechanical guy, I'll leave this one for the MEs out there. For our application, close enough was more than we needed, so we just drew the gear profile "by eye", machined it on our home-made CNC mill, measured, and iterated - only took two shots!
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Unread 04-02-2009, 00:05
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Re: FP Gearbox: Last stage gear?

Quick question I wanted to cnc gears on my cnc but what tools or bits would I need to get the job done?

Thanks in advance.
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Unread 04-02-2009, 15:34
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Re: FP Gearbox: Last stage gear?

That will depend on the size of the gear and the material. The smaller the teeth, the smaller the cutter, I assume.
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Unread 04-02-2009, 16:12
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Re: FP Gearbox: Last stage gear?

Normally this requires an involute gear cutter(or hob), of which there will be several for the same Diametrical Pitch value, as the profile of the cutter needs to change a bit due to the number of teeth. You can also grind a peice of tool steel to make a form tool and use it as a single point cutter. OR if the tooth profile is large enough, you can use a properly sized end mill to cut the gear on a 3 axis mill. However this would likely be a very hard thing to accomplish(in something other than plastic / wood), for reasons I wont go into here. So, if you have a 4 axis CNC or a manual mill with a dividing head, or rotary table look into the involute gear cutters.
If you want to search around some, another word for gear cutting is hobbing.
Here is one example
http://www.youtube.com/watch?v=VHTXa...eature=related
and here is another, using a different style cutter
http://www.youtube.com/watch?v=62yme...eature=related
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Last edited by Justin Stiltner : 04-02-2009 at 16:15.
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