# Cutting of bevel gears?

Has anyone successfully cut bevel gears that are of the correct involute form right up to the (diminishing) inner circle?
I'd been helping one of the national gear experts for some time with mathematical analyses for his gear hobbing, but now that the time has come for me to want to cut my own gears (for a Ham Radio project) I was musing how to be able to cut all sorts of gears, especially bevel gears (for a 16mm narrow gauge railway engine)
ie, now that I have reasons for wanting to cut the gears, it ceases to be a background interest / pipe dream
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Ivan Law describes a practical alternative on page 104ff of Gears and Gear Cutting. The cut is of constant depth and you make three passes to taper the width. The teeth are the standard shape at the small end and shift to stub form at the OD. He states that he method was used successfully by small job shops using standard cutters in WW1 and the teeth run smoothly together without additional fitting or running-in with abrasives. jsw
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It was as a result of reading that together with the bevel chapter of p37 et seq that set me thinking (always a dangerous thing to do :-) )
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I made a wooden lantern-wheel 'gear' drive for a model waterwheel that ran for a month until it was stolen. By then it was so covered with algae I didn't care.
That algae-filled college campus stream may have been the first scientifically investigated case of eutrophication, in 1965. It ran under and stank up the biology building so they couldn't ignore it. The biologists need a couple of weeks to figure out why the stream was so choked with algae, while we set up signs and my Rube-Goldberg bleach dispenser in light-hearted protest. The source was phosphorus fertilizer from the athletic fields.
http://www.lakescientist.com/learn-about-lakes/water-quality/eutrophication.html "First described by Vollenweider in 1968, phosphorus, and to a certain extent nitrogen, were linked to the growing problems of eutrophication."
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On Saturday, 6 October 2012 14:37:45 UTC+1, Jim Wilkins wrote:

Machinerys handbook has all the formulae, I have done a crownwheel and 3 pi nions for a traction engine without problem using the 3 cut method. it is s low and you have to have a good quality dividing head with a miller ideally with either no backlash or a DRO. The other problem is that you must repos ition the blank in the head chuck after each set of passes this can only be done by feel. If you need 'proper'bevel gears contact me as I have aquired a Gleason mach ine and plan to make them the 'professional' way Peter
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Gareth,
It might be worth your while getting hold of a copy of this book:
http://www.camdenmin.co.uk/construction-manuals/kozos-engines/building-th e-climax-p-1511.html
Kozo describes how to make a model Climax logging engine. including a detailed description of how to make the correct skew bevel gears, using normal workshop equipment. Even though the scale of his design may differ from yours, the techniques should be transferrable. The books themselves (there are several others in the series) are works of art in themselves.
David
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David Littlewood

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writes

Well, there's a thing!
I've a copy of his Shay manual mouldering unread on my bookshelf.
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Unfortunately the Shay book, being a 2001 reprint of a series of articles originating in 1975 talks about buying and fettling standard off-the-shelf gears.
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Gareth,
Yes, I believe the Climax book may be the only one to set out the procedure. I have the Climax and New Shay books, the latter suggests you use stock gears (with minor mods to shaft hole and boss) or refers you to the Climax book and says do them the same way with zero offset (these gears not being skew ones). AFAIK, the other two books (Shay and Heisler) don't have any instructions of use for you - it's only the Climax.
The instructions in that book do seem to be fairly comprehensive, with a detailed appendix discussing the theory and giving the mathematics to allow you to work out for other sizes. Do be aware though that these are uniform height bevels, not uniform profile ones (which I understand cannot be made without complex machinery). The uniform height ones, it assures readers, do mesh perfectly though.
David
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David Littlewood

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