Gallery, Projects and General > Neat Stuff
Quite a set of gears!
John Hill:
Chris, one of the interesting facts I learned is that most of the simple gears we use, such as the change gears on our beloved lathes, are actually compromises, all to do with something called 'involute' gears. Obviously every gear is different in tooth shape to gears of the same set but a different number of teeth but is it not required to have a gear cutter for each size of gear as there is a range of sizes that are designated 'acceptable'. If you use the shaper method (and I suppose there is an equivalent lathe method) the gears are actually shaped by the blank revolving in respect to the cutting tool and it is possible for the amateur (maybe even me? :scratch:) to cut spur gears that are more accurate than the commerically available ones!
I hope gear cutting will be an interesting and rewarding experience when I manage to get to that stage.
usn ret:
Wes, :coffee: I stumbled on this some time ago and filed it away for posterity. Well posterity is here, gear making, :smart: www.atmsite.org
the link as typed didn't work. If interested, go to the site and do search by author, that works.
You've got mail :thumbup:
Cliff :coffee:
bogstandard:
Chris,
I have done a little bit of gearcutting when I made new gears for an old Myford lathe. I had to make a new bull gear and another one for the back gearing setup.
For Horology (clocks) they usually manufacture their own flycutters and gearcutters to make the gear setups, and that is all usually done on a small lathe with a milling spindle setup.
http://www.csparks.com/watchmaking/WheelCutting.html
For involute gears, which is the normal type we use, and the ones I made, you buy your cutters ready made. Usually the sets come with eight cutters, to cover the whole range of teeth required. I just bought the ones that were needed.
http://rdgtools.co.uk/acatalog/INVOLUTE_GEAR_CUTTERS__SET_S_AND_INDIVIDUAL_.html
They are fairly easy to do if you have the equipment. The major bit is either a rotary table (and you need to know how to use it correctly to obtain minutes and seconds of a degree), or like I did, a dividing head, which makes it a lot easier. A very rigid arbor to hold the cutter, and a set of tables (usually in engineer tables) to give you the correct diameter of blank and depth of cut for each tooth. Once you have it all set up, it is just a normal milling procedure. But usually a rather tedious one with no disturbance required. Make a mistake, and it is start all over again.
If you want a lot of the same size, you could cut the gear profile along the length of a bar, and part off as required.
For one off's it is better that you use a gear stockist and buy individual ones, as to buy all the gear cutter sets to do every type and size of tooth form would cost a fortune.
Unfortunately, the ones I wanted were not produced, so I had no choice but to make my own.
John
raynerd:
thanks for your replies - some years ago I drove to Bradford to talk to a enthusiast/hobbyist horologist who was cutting some amazing gearing using the same lathe/mill as me at the time (unimat 3). He was using a modified dividing head accessory that can be purchased for the unimat, he then held his gear blank in a mandrel in the chuck and used the milling machine attachment with a fly cutter with gear profile to cut a gear notch. He then rotated the dividing head and therefore work piece to the next "click" and cut another gear...and so on. He was basically using the chuck on the "lathe" headstock to hold the work and then the mill to cut the notch.
When I first posted earlier in the thread I had totally forgot what I had seen and it reminded me as I was reading your replies, espcially Johns first link. It made some really amazing gearing for such a relatively simple setup.
Earlier last night when I was reading through this post I made contact with him again and he has offered me a visit a week on Tuesday. Perhaps a bit advanced for me right now, gear cutting, but I`m not going to refuse and he has said I can take a camera to snap some pics to help me remember.
Anyway - sorry I have gone well off the original topic!
Chris
Weston Bye:
--- Quote from: usn ret on May 15, 2009, 11:30:14 PM ---Wes, :coffee: I stumbled on this some time ago and filed it away for posterity. Well posterity is here, gear making, :smart: www.atmsite.org
the link as typed didn't work. If interested, go to the site and do search by author, that works.
You've got mail :thumbup:
Cliff
--- End quote ---
Cliff,
Thanks for the link. Worm gears don't bother me. Indeed, my "Time Machinery" article features a clock with a single 60:1 worm drive to derive minutes from seconds motion. Hours were accomplished with a spiral cam and a 12 step ratchet. Very unconventional. The link is a good one though, a keeper. Thanks again.
I haven't tried making spur gears yet, and my next clock still won't have any gears, worm or otherwise. Will report after it goes to press.
Wes
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