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Thread: My first fly cut worm wheel
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23rd Jul 2021, 05:35 PM #1Gear expert in training
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- Aug 2008
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- 34
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My first fly cut worm wheel
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...
PXL_20210722_005259360.jpg
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
PXL_20210723_015420141.jpgPXL_20210722_230947264.jpgPXL_20210723_015409868.jpg
Finished product looking like a gear again
PXL_20210723_024053091.jpg
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), but somehow we still delivered this afternoon as promised. 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.Gear cutting specialists and general engineers www.hardmanbros.com.au
Fine pitch gear cutting from 0.1 Module www.rigear.com.au
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23rd Jul 2021, 07:56 PM #2Most Valued Member
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- Nov 2017
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- Geelong, Australia
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Nice work!
No sniggering in the peanut gallery if this is a really dumb question, but:
Do you cut one tooth to finished depth then reset back to the start of that tooth, index the blank to the start of the next tooth, then rinse and repeat?
Steve
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24th Jul 2021, 08:29 PM #3Gear expert in training
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- Aug 2008
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- Melbourne
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Nope, the cutter spindle and work spindle are linked so each revolution of the cutter cuts one tooth as the work rotates in the same way as normal hobbing. Just have to do multiple passes to get to the proper depth.
The only time you need to change things around is for multi-start worms where the number of teeth is divisible by the number of starts, then you shift the cutter spindle across by one pitch for successive passes.Gear cutting specialists and general engineers www.hardmanbros.com.au
Fine pitch gear cutting from 0.1 Module www.rigear.com.au
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24th Jul 2021, 09:57 PM #4Gear expert in training
- Join Date
- Aug 2008
- Location
- Melbourne
- Age
- 34
- Posts
- 1,075
Gear cutting specialists and general engineers www.hardmanbros.com.au
Fine pitch gear cutting from 0.1 Module www.rigear.com.au
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