Gear Hobber

Nice videos. Thanks for posting. The feed indexing looks pretty self explanatory. Is the radial index of the shaft or gear blank based on gear ratios or is it driven of from some sort of dividing plate/spacer/indexing mechanism?


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vtcnc said:
Nice videos. Thanks for posting. The feed indexing looks pretty self explanatory. Is the radial index of the shaft or gear blank based on gear ratios or is it driven of from some sort of dividing plate/spacer/indexing mechanism?


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There is a indexing mechanism on the right side of the machine that, as set will revolve the indexing shaft one, two or four turns when tripped by the new start of cut after the quick return of the carriage, that index shaft crosses to the other (left) side of the machine to the train of change gears which are set up to determine the number of teeth to be cut, at the end of that train of gears is a shaft the runs behind the machine to a pair of bevel gears that rotate the vertical shaft seen at the right of the machine, which in turn, through a couple of spur gears, rotates the worm that gives motion to the index worm gear at the back of the work spindle. The worm is not directly driven by the vertical shaft so that it may be disengaged if needed and fine adjusted through a serrated coupling. With suitable cutters, work other than gear cutting may be done, such as slots, ratchet teeth, etc. The last video snuck in inadvertantely ---
 
When I bought the machine many years ago, it had no change gears with it, so I had to determine center distances of the feed and speed gears and what numbers of teeth suited them and what DP to use, also there was no table of change gears for numbers of teeth, but fortunately I found a table for a Brown & Sharpe automatic gear cutter that worked for my machine. There were 36 gears for indexing, including 3 for prime numbers such as 127 for metric transposing, 15 for speeds, which could have been fewer, and two for feed speeds. Lots of gear cutting on the milling machine before the automatic could be used. When I sold the business, the new owner did not want the machine and several others so that I brought them home, otherwise some of them would have been scrapped.
 
Here is the video. I ordered the plans $70.00 deductible if you buy the entire kit. The kit only includes the casting many more parts are required for completion.

 
So I just found this thread :) I actually bought the plans and castings, and have started working on it here: https://www.hobby-machinist.com/threads/erichs-benchtop-gear-hobber-project.101649

As others have said, the plans are pretty mediocre quality, but the castings are lovely! At one point, I'd love to figure out what the entire set of gears needed to 'self make' a set of gears are, so I can get them 3d printed (thus the first project for it would be to make its own gears :) ), and how to use the change gears, but thats a problem for much later in the project.
 
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