Gear Making

[Steve Shannon]

My question was not meant to be critical and I apologize if it sounded that way. I would love to learn how to cut gears. I've watched nearly every you tube video on the subject, but I haven't seen any where someone was making more than one of a particular size. Boring a long gear blank like that might offset any savings anyway. I would think a person would turn the blank and then groove it below the gear teeth root. Then cut the teeth and finally finish parting it off. That would avoid having to make an interrupted cut.
I have a couple helical gears that are each missing a single tooth. When you do cut the helical gear I would love to see how you do it.


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[Nebraska Kirk]

Steve, not to fear, I did not consider your questions to be criticizing, merely legitimate questions from someone wanting to know. A helical gear will be more involved... the power shaft of the dividing head will have to be geared to the leadscrew on the table so that as the table travels in the X axis it will rotate the dividing head to form the helix. Careful calculations have to be made to determine the lead of the helix and to get the correct gear ratio to form that helix. The cutter also has to be set at the angle of the helix. Then there is the task of determining what cutter to use. The normal pitch (pitch of cutter used) will vary with the helix angle. The Machinery's Handbook gives the procedure and formula necessary to determine the normal pitch. Finally, the correct number of cutter in that pitch must be calculated. The proper milling cutter to use for spur gears depends upon the pitch of the teeth and also upon the number of teeth, but a cutter for milling helical gears is not selected with reference to the actual number of teeth in the gear, as in spur gearing, but rather with reference to a calculated number that takes into account the effect on the tooth profile of lead angle, normal diametral pitch, and cutter diameter. Clear as mud!? That is why I have a copy of the Machinery's Handbook, all the mathematical formula and tables are in there!

Videos of the machining process.