In the course of my somewhat rushed training to learn literally everything about cutting gears in the space of 2 weeks, a rush custom job came in the door yesterday. Unfortunately, a communication breakdown meant that we weren't told to prioritise training over an insane deadline (boss says "I told the customer he can have them tomorrow", foreman says "are you kidding? we might still be making the tool tomorrow"), so I didn't get to actually make the tool, but at least I got to watch it happen and hopefully absorb some of the principles. The fact that we had an existing tool bit already saved us a couple of hours though.

This used to be a worm wheel...
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They made up an extra test piece in ally for me to (potentially) stuff up on, fortunately that wasn't the case, then the real ones in aluminium bronze. The drivetrain is set as it would be for a helical gear using differential feed, but, instead of driving the column up the face of the gear, it drives along the cutter axis tangentially to the gear being cut. The tool bit is welded in to the shaft because of size restrictions; on larger worms the bit would simply be held in place with a grub screw
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Finished product looking like a gear again
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Start to finish to set the machine and cut 3 parts took 7 hours and that's not including any of the calculations (add at least another hour) or making the tool (2 hours with the existing bit, 3-4 from scratch). Worms are hard

Even though I didn't get all the training I would have liked out of this job, if it hadn't rocked up when it did I would probably never have learnt it at all.
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