Driving a Universal Dividing Head

You're describing mechanical methods to run the dividing head. Clumsy at best. A better way has been explored - using electronics and stepper motors.

Don Foreman is building a "brain box" for me shortly to drive the dividing head with a stepper based on pulses from an encoder placed either on the spindle or on the table axis. A fellow named John Stevenson has a prototype up and running. He's hobbed several gears last time we cooresponded. Don has designed an improved version (For those that don't already know - Don is an electronic guru)

Here's a long thread that ran last December on the subject:

Karl

Without the swiveling table I think your only option for helical milling would be with end mills.

If you have lever feed, you can't run the dividing head with the feed. If you have a feed screw, however, you should be able to run a gear train from it to the dividing head. Still, you'll need the swivel table if you use plain milling cutters, unless you don't mind them wallowing out the sides of the cut.

John Martin

Enco also sells a universal dividing head, still pricey for an import. I've used it in helical milling, but as the parts were to move 2" in

180 degree rotation, we drove the bridgeport feed from the dividing head. Pretty simple setup, we wanted ten turns of feed rotation to 20 turns of the dividing head crank, or 1:2 ratio. Used the same process and a form cutter to make steering worms for an old IHC tractor, worked pretty well and no more difficult to set up. For something with less helix angle, the gearing might become compound, making it a little more brain intensive, but not impossible. Not rocket science and has the benefit that most places have one gathering dust because most people never knew how to use them, and the rest forgot.

Just thinking, perhaps I didn't answer the question, the dividing head is either driven by, or drives, the leadscrew through the gear train.

Clumsy, it is NOT. Simple, requiring only that the person setting it up is able to calculate gear ratios, and I have never heard of a gear breaking in this usage. Electronics and steppers, well, it's a Micro$oft world. It should operate at least as well as windoze. Mechanical was "Old Tech" before the first computer, and refined to an amazing degree. Steppers and electronics, I've seen CNC rotary tables, which sometimes worked as they were supposed to, but usually not.

Simply put, it will probably spend most of it's time gathering dust, but when you need it, you need it. Blow off the dust, put some oil where needed, set the gearing and go. When you're not using it, it's not eating anything. Long term storage of electronics has improved immensely, but is still a long way from the storage life of a gear.

Ah, thanks. So then I guess I'd have to make up a custom adapter to mount the drive gear. It just makes me nervous to think that I have to buy the dividing head (the AccuPro is around $1100. My miller cost less than that!) before I can find out how to mount the driving gear.

Yeah, I have the vertical head. I also have a complete set of gear tooth cutters for the horizontal arbor, so I'd love to score the swivel table guts and retrofit this machine with them. Do they make end mills with gear tooth profiles? Never heard of such a thing before, myself.

It's a screw feed, with a possible motorized power feed in the future. I guess it's down to making up some sort of adapter to mount the gears to the screw feed shaft. It's good to hear, from another poster, that you can operate the linked table feed via the dividing head crank. That opens up more gear mounting options.

If I ever find a UM junker with good swivel table guts....

Not being intimately aware of the whole setup, but I think I have the concept, so I hope this isn't a dumb question....

Wouldn't a subplate mounted on a large rotary table work? Other than the added height, I can't see a real drawback to this. Again, I might be missing something entirely and this is a dumb suggestion. I suppose if you had a big enough rotary table to mount all of your tooling a subplate wouldn't be neccessary, but I suspect it would get too big for the table before it got big enough to fit the dividing head and ....

JW

Many of the old machinist's manuals have instructions for setting up the dividing head. It is usually described as if the dividing head were generic. Paul

Artemia,

I have done exactly what you are trying to do with your mill. I am familiar with the TM. I have a Burke #4 horizontal mill (smaller than the TM) with a universal table and a Rusnok vertical head. I have a P&W universal dividing head with the set of change gears and brackets. You will need a true universal head with the change gears and brackets. I have used the dividing head connected to the table lead screw and the vertical head to mill cams. You will be severly limited trying to do helical work without the universal table. The connection from the dividing head to the table is relatively simple with the gears and brackets. The biggest problem you may encounter is adapting the shaft on the table lead screw for the change gear. My lead screw was a match 1/2" shaft w 3/32" keyway. The other end of the table has a typical Bridgeport type Servo feed for power table feed. I have also built an adapter for the mill using change gears and a 40:1 reduction box to hobb gears using the mill. A dividing head could be used in place of the reduction box.

If you don't have one, I'd strongly recommend getting "Treatise on Milling and Milling Machines" by Brown & Sharpe. They can be found on Ebay or on line used booksellers. It shows exactly how the set ups are made. It also has lead tables for the B&S mills. If your lead screw is not 4 TPI as on the B&S the table conversion is simple. My lead srew is 10 TPI so the conversion factor is 10/4=2.5. The tables are for any dividing head that has a 40:1 reduction.

The norm is to replace one of the cranks, temporarily, of course, with a bushing for the gear, keyed to fit the screw and keyed on the OD for the gear. Just think of the simplest possible way to do it, that's probably how it's done.

For helical milling with a standard milling cutter (not an end mill) - which is the way it is usually done, the work has to be set to and feed at the angle of the helix. Which is why you need the swivelling table. Or a mill with a swivelling head.

John Martin

It isn't a dumb suggestion, but it won't replace a swiveling table. The table itself needs to travel at an angle to the milling cutter when milling spirals on a horizontal miller. Now an accessory X-Y table (like some use on drill presses), mounted on a rotary table would work - conceptually at least. You'd actually only need the X-axis motion from it. That would be too bulky for my little miller but it would provide the necessary direction of travel.

It's a hard concept to picture unless you've seen it.

Thanks very much, Joe. I'll get a copy before I make any purchases.

This makes sense. I hadn't thought the whole idea through. I do know of such a beast (rotary xy table) but it is huge in comparison to my mill. Not that I personally can think of an immediate need to do what this is needed for.

Thanks

JW

When milling something like a helical gear, the table of the mill has to be angled to match the angle of the helix of the gear, or you won't get the form that is ground on the cutter, but something else, usually not what you want. With a vertical mill, the cutter is centered over the piece, and normally, if there is any form other than a straight sided slot, the form is on the cutter. As it's always on center, it doesn't change the form. Helical gear generation can be done on a vertical mill with a right angle head, but the head can be turned to match the helix angle.

milling > > Wouldn't a subplate mounted on a large rotary table work? Other than

Now, Think about using a vertical (Bridgeport style) mill with a conventional (horizontal style) cutter, and tilt the head left or right to match the helix angle. Using a stub arbor.

This is the exact equivalent of using a rotating table universal mill.

Now, lining the cutter up on center is simular, but "sideways" to setting up the cutter on center for a universal mill.

No universal mill needed. No angle head needed. Just a normal vetical mill.

Pete

Didn't even think about that, the head on my A1-S is hard enough to tram that If I can find any other way to cut angles, it beats having to tram the head again.