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Hobbing baby bevel gears
Thought I'd share this as I'm guessing most people here wouldn't have been exposed to this sort of specialised work.
One of my recent jobs at work was cutting some small brass bevel gears (I think the pitch was Mod 0.4) on our Mikron 120.01 bevel gear cutter
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The process is essentially the same as hobbing in that the cutter and workpiece are synchronised in rotation as the work is fed across, but there are a few key differences in the cutter itself. The cutter just has 2 wings that form the teeth as opposed to a proper hob, there are also a range of cutters for each tooth pitch, much like the different numbered gear cutters for mills, which are chosen based on the size of the gear and the number of teeth to be cut. Another major difference is that each wing cuts only one flank of the gear teeth, so the cutter needs to be centralised with the aid of a microscope attachment (which I was firmly told to NOT drop at any cost :rolleyes:, this machine is some 50 years old and spare parts don't exist)
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All the cutting parameters are set via a gear train, the cutter spindle is tilted over to the helix angle of the cutter and the work spindle is set to the required pitch angle of the gear (in this case, 45 degrees)
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There's a deburring attachment to clean up the back of the gear as it's being cut, a hard stop for the starting position and an automatic stop as well, so it's simply a case of loading each blank on the arbor (which is held in a collet and adjusted to a maximum of 0.0005" total runout) and flicking the start lever.
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Some 90 seconds later there's a finished gear
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Attached Images
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