I have always admired (and wanted to build) a complex dedicated gear cutter I had found in an old Model Engineer. I don't remember the exact name, without researching through my boxed issues, but it was a series of articles.
But thinking about that, now, the real reason I wanted to build a gear cutter in the first place was that the cost of bevel gears was high, and I wanted to build Westinghouse style steam engines, which generally require them for driving the steam valve. Good quality bevel gears are very expensive thee days. It was one of those times when you get seduced by the idea of building a major tool to do a different project you are actually interested in.
I was thinking this morning about how we tend to generalize and build multi-purpose tools, and ignore the possibility of building a much simpler single purpose machine tool. If I were pursuing it In the case above, it would be a simple bevel gear cutter for gears of at most 2" (50mm) in diameter.
It's true I could probably make a fixture for my mill drill that would do the job with lots of fiddling, but the idea of a single purpose powered tool that just cuts bevel gears somehow appeals more. I also don't have a rotary table. Need a bevel gear? Pull out the bevel gear tool and cut one -- not lots of reconfiguring the mill drill table with fixtures, locating cutters, setting up heights, depths positions, etc. And then when it's over taking it apart,
I dunno, maybe it doesn't make sense to anyone else, but I just like the idea of having something that, out of the box, does a straightforward job. Because it doesn't have to do anything else, it can be simple and compact, with a minimum of settings.
Small bevel gears generally don't have wildly different tooth numbers, so an indexing plate with a few sets of holes will do for that. They generally have a very limited set of bevel and pressure angles. You could get away with one each.
The main topic of interest would be wedge shape of the teeth. These converge on some imaginary conical center. If the cutter was thinner than the inner space between the teeth it could cut each tooth with two passes along a radial of that cone.
Ideally a controllable speed small motor with direct drive to the cutter would be simplest. Cutter axis would probably be horizontal, and gear axis vertical. But it could be the other way around if that worked out better.
This is just noodling an idea. I'm not ready to build one yet because my shop needs major work to become useful again. But I like the idea of single purpose machine tools because they can be built simply, cheaply and be compact. They don't have to accommodate large objects, or perform flexible and complex tasks like a lathe or conventional mill does.
How would you build a mechanical standalone bevel gear cutter of the size and range I'm talking about here? Ideas and sketches are welcome.
Yup, I know I could cut gears on my lathe or mill with fixtures, or program a CNC mill to do the job. But that's not the project I'm interested in. I'd like to know what's the simplest most compact single purpose machine we could come up with, and especially if it could use scrap material or existing small motors.
Any takers for this design challenge?
