- Thread starter winchman
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Yes. Single tooth gear cutters, for cutting gears using a dividing head.
It's worth noting they don't typically produce a perfect gear, as each cutter typically covers a range of teeth, unlike a hob which will generate a perfect gear regardless of the number of teeth. But running a hob involves a far more complicated setup.
It's worth noting they don't typically produce a perfect gear, as each cutter typically covers a range of teeth, unlike a hob which will generate a perfect gear regardless of the number of teeth. But running a hob involves a far more complicated setup.
Agroshield
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Can you post some clear pictures of the writing on them.
There are at least three sizes (DP) of cutter there: I could see 32DP (top right), 34DP (second down, right) and 40 DP (bottom left). The 34DP one says 'BE Standard' and I am not sure what that is. Second down on left has been resharpened almost to extinction.
There are at least three sizes (DP) of cutter there: I could see 32DP (top right), 34DP (second down, right) and 40 DP (bottom left). The 34DP one says 'BE Standard' and I am not sure what that is. Second down on left has been resharpened almost to extinction.
Essentially.
All you need is a suitable milling machine, an arbor for mounting the cutter, and a dividing head (or some other suitable way of mounting the stock and locating each tooth), which is far simpler than the rotating workpiece synchronised to the cutter, and the need to have the workpiece angled to match the hob lead angle.
I love the proper old school mechanical hobbing setups. I've got a couple books on gear cutting, and the universal hobbing machines are just a mass of change gears, gearboxes, and driveshafts. They must have taken hours to setup.
Although I don't think hobbing is as popular now, unless the flexibility of being able to produce multiple gears from a single hob is needed.
Most are produced via planing, which will rattle out gears far quicker than a hob.
For general trivia knowledge, you don't machine a gear, you generate a gear.
Gear companies produce gears from hobs - had to pay a few grand for specific hobs for jobs over the last few years.
Its a science I know now I know next to bugger all about, having spent 20 yrs thinking I knew a lot, having had to work closely with a gear company and the Design Unit at Newcastle unit where the gear standards are kept over the last couple of years.
Its a science I know now I know next to bugger all about, having spent 20 yrs thinking I knew a lot, having had to work closely with a gear company and the Design Unit at Newcastle unit where the gear standards are kept over the last couple of years.
winchman
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I will clean them up over the weekend
northwest
Searching for the Holy Grail.........
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I am right there with you on that, I know a great deal about a small number of things, I know less than nothing when it comes to gears. I have long since concluded it is best to ask someone who does know rather than bugger it up then ask!
Gears are sorcery really.
mtt.tr
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Chap i worked next door to when i was an apprentice did a lot of 1 off gears, he was seriously bright
Agroshield
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Sort of.
When the term 'generate' is used in machining, it means that the relative motion of cutter and workpiece are strictly geometrically correct to produce the required shape. You can generate lots of things in additon to gears.
You generate a cylinder or cone on a lathe as the tool and workpiece have the correct geometric relationship. You generate a flat surface on a planer or shaper. You can generate an ellipse using various methods (e.g trammel of Archimedes). You can generate a spherical surface on a mill using a rotary table and a boring head.
In gear cutting (and associated finishing processes like gear grinding), there are two basic processes to form the tooth spaces: form cutting (using cutters as above or variants thereof) and generating (using things moving in the correct relationship).
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The best home workshop level book on the subject is Ivan Law's Gears and Gear Cutting. After that, Colvin and Stanley Gear Cutting Practice.
See: https://archive.org/search.php?query=gear+cutting&and[]=mediatype:"texts"
Pete.
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You can cut a gear any way you please it's just a piece of shaped metal. Wire EDM produces (can produce) lovely gear finishes.
Those 32DP are quite a popular size but they are still not worth a great deal each.
Notice the d&f (depth plus clearance) value for the 32DP is exactly double the d&f for the 64dp? That's because the 32dp teeth are twice the size of the 64dp ones. The relationship holds true across the entire range of standard tooth sizes it's just how they work hence the term 'diametral pitch' - the number of teeth on the circumference at 1" pitch diameter.
Those 32DP are quite a popular size but they are still not worth a great deal each.
Notice the d&f (depth plus clearance) value for the 32DP is exactly double the d&f for the 64dp? That's because the 32dp teeth are twice the size of the 64dp ones. The relationship holds true across the entire range of standard tooth sizes it's just how they work hence the term 'diametral pitch' - the number of teeth on the circumference at 1" pitch diameter.
I've got the Colvin and Stanley book.
I think it pretty much covers everything you'd ever want to know about gears, and has quite a few diagrams/photos of gear machines.
Things like this -
Which you can pretty much recreate with an encoder, 4th axis, and a pretty basic controller now.
I'm sure a search for some of the now departed John Stevenson's posts over on some of the model engineering forums (possibly the HSM magazine forum) will show the digital setup he had for gear cutting with a hob. IIRC it used a basic encoder on the spindle, a stepper driven rotary table, and a basic version of LinuxCNC with a screen to set the required ratios.
I think that's what he originally used, but then somebody created the LinuxCNC setup, where IIRC you simply entered the hob details, and teeth number, and it done the rest.
I can remember seeing a couple photos of the screen, but there were other iterations before that.
Curiosity got the better of while waiting for a print to finish, so here's some more details on JohnS's setup - John stepper motor gear hobber. - The Home Shop Machinist & Machinist's Workshop Magazine's BBS
mtt.tr
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He just used frequency counters if i recall
