how to use a rotary table and dividing plates made in china

The way that I was taught is that you have to make up a test bar. Take a piece of 12" by 1" roundbar, drill two centre holes in it"s ends, on your lathe and take a parallel cut between centres. Once you have corrected the error of your lathe and both ends of the test bar measure the same diameter, you can then use the test bar in your milling machine as well, to set the tailstock of the dividing head as well as the alignment of the bar to the table axis.

Say you want to cut a 51-tooth gear, or 51 splines, or evenly space 51 holes on a bolt circle: 360/51 gives 7.05882 degrees, or 7 degrees, 3 minutes, 31.8 seconds - and your rotab measures to (f"rinstance) 1/10 of a degree - tricky to get it right!

you rummage through your dividing plates, looking for something with a common factor with 51 - its factors are 17 and 3, so you want a multiple of 17 (the 3 is a factor of 72 so that"s covered already) and you find a plate with a 34 hole circle ( 2 x 17) and fit that;

The table"s ratio is 72, and you"ve used the factor of 3 in it, leaving a factor of 24 - into the pot and multiply by the 2, giving 48 holes "but I"ve only got 34 holes!" you cry!

48 holes is a full turn plus another 14 holes, so set the dividing sector arms with 14 SPACES between them - the first hole counts as 0 as you haven"t moved from it, so you"ll have 15 HOLES between the arms, then bring the "lagging" arm up to the detent pin, take a full turn and the fraction to the "leading" arm - you"ve done 48 spaces, exactly what you want! now make your cut, move the sector arms around again, take a full turn and a bit, next cut etc. etc. etc.

Because you"re mechanically DIVIDING rather than guessing using the dial on the handle, your cuts will be in exactly the right places (important for gears or dials!) - if you don"t have the right plates you can do much the same to make "em, each time you go through the dividing process the accuracy will improve:

Say you need a 50-hole plate (maybe making a dial for a tailstock handwheel), 50 isn"t in the set of plates, nor 25... So you make a rough plate (old CDs work well

This is pretty much how the first dividing plates (and, incidentally, threads) were made, repeated division of the errors, and why we don"t need a "master plate" in a national standards lab" somewhere to compare our divisions against

I ordered a 6 inch from Busy Bee a few years back but it was complete junk. The pinion gear had some broken teeth after a few uses. I admit I am slightly ham fisted at times however I was really disappointed in the quality.

Perhaps there is a faint but unmistakeable whiff of pedantry. I have one of these daft things called a cheap and quite nasty thing with a silly little lazer and a set of spirit levels and it is ever so nice because I think that is was a quid which is the Brit way of saying it cost a dollar and a half. I sing to it "Shine on Harvey Moon" and it actually works. To think that I bought a Vertex thingy- me- jig and made a RT for my Myford and bought a another one to fit my mill and then made a fancier affair again to fit my Quorn and then someone gave me one to do radius malarkeys on my Clarkson- and it tilts and faces mecca or somewhere.

Methinks that some of us should stand back and ponder. I spent a weekend looking at the works of the great artists and it dawned on me that they all had a few tatty paint brushes and the great sculptors had a chisel and a battered wooden mallet apiece - and were probably half drunk most of the time- because the Roman water was full of malaria bugs.

I bought this item directly from Grizzly to use it on my LMS 3900 mini mill. I didn"t have an immediate need for the indexing feature, but thought it might be useful on later projects. I don"t even know how to use the indexing function so I have no idea how good or bad the indexing feature of the table would be.

-the gearing had such a tight spot that it was virtually impossible to crank the table around unless you allowed several degrees of gear lash in the table.

Not being very happy with my new purchase I called Grizzly. They were very nice on the phone. I described the problems and asked if this was typical of these rotary tables. The point being if they were all like this I would get a refund, but if not then I"d try a replacement. The tech said he had used many of this very model and they always worked well. That was encouraging. A few faulty items can always slip through production. The tech even told me not to worry that Grizzly would open, inspect and check the new one for function before they shipped it. Sounded good to me. I sent it back for a replacement.

I called a few days later and spoke to Grizzly again. They said they had received the table and inspected it. They found all the faults I had described and were sending another out that day. Super. I was sure I"d get a good one this time.

I got the replacement today. First thing I noticed was that the box was still sealed like it had never been opened since it left the factory. When I opened it the parts inside were still sealed in individual plastic bags. These are not ziplock type bags, but sealed bags that must be cut or torn open. There is no way Grizzly inspected this like they promised. It gets worse.

When I unpacked everything I found that the pin on the shaft that allows the crank handle to turn the shaft and thus rotate the table was missing or sheared off. There is no way to rotate the table. This one was even more useless than the first.

I called Grizzly again. They were very nice this time too. The person I spoke to said that the notes said it had been inspect prior to shipping and that the table "...functioned well, but was a bit tight. It would loosen up after it was broken in." This is obviously not true. Not only was it apparent from the packaging that it had never been opened, but the missing pin prevented anyone from testing the item. The crank handle could not turn the table.

This one will be shipped back tomorrow for a refund. Hopefully, I"ll get my shipping refunded too as Grizzly promised, and a full refund. We"ll see. At this point I"m less than confident in what Grizzly tells me.

Some may say that $175 is cheap for a rotary table. That"s true enough, but I"d like to make a comparison to the mill I bought from LMS for $790. It"s made in China too, and it"s not perfect, but it functions as advertised. I feel I got what I paid for with the mini-mill.

when I was young, strong, healthy, and thought nothing of lifting it, a 10" H & V was my first choice. I still think it was a good choice for the work I mostly do, and this is where you may decide to compromise. If you do small work, an 8" table is much lighter and more convenient to set up. Stood vertical, it interferes less with the spindle to reach center. I don"t think a 6" is a good choice unless you know you will only be working miniature stuff. You use a considerable percentage of a small table just for set ups and hold down clamps on a lot of work, and a small table does not leave much room.

I like 90:1 gear ratio for circular milling, which is presumably your primary interest with a rotary table. My 10" table is 90:1, and that is a pretty good ratio for milling diameters (hand cranking) out to 12" or so. My 20" table is also only 90:1, and out near or past the rim (I do one part at 32" diameter) that always seems _very_ coarse.

If most of your work is small, round to begin with, and will actually be dividing work, where you index the table, lock it, and then drill a hole or mill a slot with the machine axis drive, you might find a dividing head more useful. For instance, I"ve made gears on a vertical rotary table, and in a spin index. On the table, you need an insert collet chuck or other arrangement in the center hole to get the work out far enough to clear the cutter. It"s a lot more convenient on a dividing head. OTOH, I don"t find it fun or convenient to do much circular milling on a dividing head if the work diameter is much over a few inches.

Dividing heads typically are 40:1, so faster to index, position to positon. But the milling capability on a radius is limited by the "coarse" ratio to smaller diameters, as is the usual work holding (collet or chuck) arrangement. A dividing head will tilt from below horizontal to past vertical, so you can mill, drill, bore or shape profiles at any angle in between.

an 8" H & V with dividing plates and set up, can usually be arranged somehow to do most of the work you might want to do on it. It is relatively light to move, and convenient to set up with reasonable space (spindle clearance, e.g.)limitations to be considered. A little bigger (10") is better, if you will ever need the capacity.

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

Dial machine—Original, Circa 1790. This is a French style tool. These were used to mark the seconds and minutes on the face and to lay out the roman numerals for the hours that were used at the time

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What?!? Nobody else gonna admit it? I"ve got a Lathemaster rotab. It"s the 8" model, though. I bought one with my mill. I got the dividing plates at the same time. It"s a "Bayard Industrial" which I believe is made in India.

I"m a computer programmer w/o any exposure to other rotary tables, but I suspect that others, even "cheap" ones, might be smoother. This one does not contain oil in a gearbox. The gears are greased, but no oil sump(?) per se. The dividing pin doesn"t line up very well with the dividing plates, and the one piece (cast iron) that is supposed to help you counting off spaces while using the plates broke before I got "round to using it.

That said, it is functional, and will do the job for which it is designed. There are frustrations present that you might avoid with others, IMO. Penn Tool handles Bayard Industrial if you want a price comparison. . . .