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Thread: Rotary table vs. dividing head
08-28-2011, 05:55 AM #1
Rotary table vs. dividing head
Newbie's question, but...
If you had to chose between them, what would be your choice?
There are surely uses where the one or the other suits better, what are the pros and cons?
Background of my question:
I have already a cheap small RT, but I found in my "scrap box" an old used 1:15 ratio worm geared angle drive (term?). I disassembled it to check its condition inside. The four 6304 deep grove ball bearings have to be replaced, as well as the 2 radial seals. It looks very sturdy, a good base for transforming to a dividing head. If it makes sense...
08-28-2011, 09:50 AM #2
i was recently in the same position. i was leaning dividing head but then went with a simple homemade indexer that i can just make plates for(thanks Mcruff!) it`s not like i do a ton of indexing. i just want to make my own gears and stuff. total cost-$ 0 -
08-28-2011, 09:29 PM #3
Depending on what you need to index and how often, a lot of numbers can be done easily on a rotary table (anything that's a factor of 360 is really easy), which I find convenient for things like drilling holes on a PCD so use for all sorts of jobs. It is worth looking at the gear ratios of dividing heads and of rotary tables - I didn't and have ended up with a table with an odd ratio and an odd minor increment on the vernier scale (I think it's 25s seconds so even getting whole minutes is impossible).
A lot of rotary tables can easily be converted to do dividing by modifying or replacing the handle with dividing plates and an indicator arm, so if it's something you might need occasionally and not to start with, it might be worth starting with a rotary table and converting it later as required. It is also possible to use something with the right number of holes (or indentations like a gear) on the spindle with the item to be machined and index from that by making a detent to fit the holes/teeth. For example, if one needed to make a 127 tooth gear for metric threading on a SB 9" because such a thing were not available where they live, but it was possible to get a 127 tooth gear to fit some completely different application (different DP or pressure angle, possibly a module gear rather than a DP gear) then that could be attached to the same shaft as the gear blank to be machined and used to index the blank for each cut. You don't even need the worm drive of the rotary table for that, just some thing to lock the shaft in each postion.
Some dividing heads (universal) have advanced functionality beyond indexing using plates, they can be fitted with a compound gear train to acheive numbers beyond the scope of the plates, or to connect to a feed (on a milling machine generally) which enables cutting of spirals (i.e. cams).
I am not sure if 15:1 is a useful ratio for a dividing head, it's too coarse for a rotary table at 24 degrees per rotation (72:1 is more normal, 5 deg per rotation, I think mine is 90:1) but that's not necessarily such an issue for a dividing head. I would say if you have the parts it's a nice project. 6304 bearings are not hard to find - I use them for some of my kite buggy wheels, I think they are about £6 each in stainless, fortunately I don't need those wheels for the Euros next week because all 6 bearings seem to be seized, I will need 6 off 6004's for the wheels I will be using though - none are seized but they aren't feeling very smooth, probably got some sand in!
I'm not sure if I really answered your question, for occasional use you can get away with a rotary table as a dividing device, possibly vice verse although most dividing heads are not as easy to use in both horizontal and vertical orientations as most rotary tables (exceptions on both sides!), but if you are looking for something to do with the worm drive you have I reckon it would probably suit a dividing head better. I'll try andremember to look in my dividing book later and see what ratios are commonly used - unless you can find the same info on the internet sooner
08-28-2011, 11:33 PM #4
It just depends on what sort of things you make. I use my dividing head way more than my rotary table, in fact I hardly use the rotary table at all. My dividing head is a small B&S copy with threads that fit my threaded back chucks. I'll very often rotate the dividing head up, put a chuck on it, and do bolt circles on lathe parts. I make gears with it. I put flats on shafts and slot screws. I don't think I've ever used the little adjustable-every-which-way tailstock for the thing, preferring to use chucks, collets or whatever. Even small gears get cut on a stub arbor, not between centers, though that's the more accurate way. OTOH, for anything large you'd want a rotary table.
Last edited by Conrad Hoffman; 08-29-2011 at 07:40 AM.
08-29-2011, 01:23 AM #5
I porchased an 8" Vertex Horizontal & Vertical rotary table with the factory dividing head conversion, basically a set of plates and fingers, along with an inexpensive import 5C spindexer. My intention was to add pukka dividing facilities to the spindexer by adapting the Geo.H.Thomas Versatile Dividing Head design to the spindexer chassis ending up with something very similar to the small Senior unit. I figured that gave a good set of permutations between indexer, rotary table and dividing head functions along with choice of collet, chuck (on a 5C spigot) and faceplate mountings without spending too much. Especially as I got a 5C collet set with my Heavy 10. Mostly ready to go straight out of the box too.
Never happened as a redundancy payment meant I could afford a larger shop, Bridgeport and Cincinnati clone dividing head.
08-29-2011, 05:16 AM #6My intention was to add pukka dividing facilities
Don't make any sudden movements toward the mango pickle.
We will need to take those samosas in for testing.
08-29-2011, 06:21 AM #7
Thank you for your exhaustive replies.
I thought so, that for example a chuck is normally used to be attached to a dividing head but not to a rotary table.
A DH is (can be) fixed quite safely in a given position, while my RT has only a tiny setscrew.
Or am I totally wrong?
What OD a DH usually has? I assume at least 25-30 mm. My angle drive has only 20. I guess it wouldn't be enough holding the same chuck as of what I have for my 9" lathe.
08-29-2011, 11:09 AM #8
I have a chuck mounted on my rotary table most of the time - not one off my lathe, it's a 4" chinese one that I got in a bundle with the table. Most tables have a taper hole in the centre an RDG sell adapters that fit most small rotary tables with a spindle thread to suit Myford or Boxford lathe chucks (note Boxford is the same as South Bend 9"). In my case the table has 3 T-slots and the chuck is front mounting with 3 bolts that fit the T-nuts perfectly (like I say it was sold as a bundle). The flexibility of being ably to clamp things directly to the table is useful, but often I will use it with the chuck to hold round work even if I am not actually going to index it.....
My rotary table has a reasonable locking lever - I'd say that was essential for both, having set a position you don't want the device moved by tool vibration.
I guess the output shaft size for a dividing head varies depending on the size of the dividing head, you should be able to make adapters to fit your chucks, they need to be quite rigid to hold the work steady but they don't have to rotate at speed or anything like that
I think though the biggest issue is likely to be the drive ratio - it seems that 40:1 is normal for a dividing head and is also the lowest rotary tables tend to go to. Your 15:1 will not be unusable, but it will require more thought