how to use a rotary table and dividing plates quotation

Dividing heads allow you to divide a circle into equal fractions conveniently. Anything that involves regular action around a circle is a candidate for a dividing head.

A rotary table has no stops so it is not convenient to do large numbers of things at equal intervals because you would have to painstakingly determine the interval. Also, the rotary table does not divide the circle. For example, if you were making 13 equally spaced operations using a rotary table you would have to calculate some wierd angle for each operation and dial it in--a tedious process. For example, here are the 13 angles for a circle division:

Do you want to manually set each of these values? Have fun doing that. Now, imagine doing it for 53 divisions. You will be there all night. Not only that, the error will be a lot more than a dividing head.

They both use worms to rotate in precise increments. The difference is in the details as each is set up to be better for different tasks. But, yes you can divide on a RT. Many, dare I say all of them, can be fitted with dividing plates. Or you can just find the angular positions and go to each of them in turn. That may be more prone to error than using plates and an arm with a pin, but it does work. I have done it.

Is the size of a RT really in the way. Well, perhaps, but I have never been unable to work with it and I have a 10", which is BIG. And heavy! I dropped it once. Big ding in the floor, no noticeable damage to the RT. It is BIG and MASSIVE. And probably a lot more accurate than most dividing heads.

PS: If your RT did not come with dividing plates and none are available, you can make a set using the table itself. I previously posted this elsewhere, so I am quoting myself;

You CAN make a set of circles on your own, using ONLY the dividing head or rotary table you already have. They WILL be just as accurate as your worm gear is, with a small bit of random error due to the uncertainties of the machining process. I have described this process several times and you can search this site (Activity Stream - The Home Shop Machinist & Machinist"s Workshop Magazine"s BBS) for these lengthy explanations, but here are the short strokes:

As someone stated above, a second generation plate made with YOUR existing head will be 30 (or 40 or 90) times more accurate than the first generation plate used to make it. The worm gear acts as a "precision amplifier". So if you have a one degree error in a first generation plate, the second generation plate will have only a 2 minute (1/30 of one degree) error. And when you use that second generation plate, the error on your work will be only 1/30 of that or 4 seconds of arc. I will guarantee you that your worm is not that accurate and no further precision is needed.

1. Make a first generation plate using any layout technique that you want. Literally ANY technique: the accuracy DOES NOT MATTER. If you can get the holes within 2 or 3 degrees of the correct positions that is 100% good enough. You do not even have to drill these holes, simple pencil marks on a paper disk and a pointer on the shaft will work. And by "will work" I mean that it will provide the accuracy I have stated above on a third generation plate.

That"s it, you are done and your work with this second generation plate will, WHEN USED ON YOUR HEAD, will be the third generation and will be at the accuracy that I stated above (4 seconds of arc or better plus the error in your worm). Thus you have made one "paper plate", the first generation and a second generation metal one.

One small note. The second generation plate made above is not at the high level of accuracy I claimed above BUT it will provide that level of accuracy when used on your head. If you want a highly accurate plate for direct use instead of one to be used on your head, then you would need to make a third generation plate to get that accuracy.

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TitlePrices of New Machine Tools: As of March 1, 1941 (revised) Used to Establish Maximum Price of Second-hand Machine Tools as Defined in Maximum Price Regulation No. 1

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A rotary table is a precision work positioning device used in metalworking. It enables the operator to drill or cut work at exact intervals around a fixed (usually horizontal or vertical) axis. Some rotary tables allow the use of index plates for indexing operations, and some can also be fitted with dividing plates that enable regular work positioning at divisions for which indexing plates are not available. A rotary fixture used in this fashion is more appropriately called a dividing head (indexing head).

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I have seen a Rotary Table with dividing plates at a good price, what are the advantages of a Dividing Head over the Rotary Table. I know that a chuck can be fitted to the Rotary Table, it seems to me they do the same job.

Check the rotab can be mounted on its side or you have a big enough angle plate. Sometimes the extra diameter of the rotab gets in the way but otherwise it is just as capable as a dividing head until you get to the more complex "universal" type that can tilt and do differential indexing for prime numbers, or be driven to make spirals.

A rotary table is a very useful but not often used device in most workshops, takes up space as well, I know, as I have one together with the dividing plates. Be careful using the tables for gear cutting as there are some with errors and its very annoying to find that you have a thin tooth for no fault of your own. Recently I made a stepper motor Arduino controller from the article in Model Engineer Workshop issue 249 which I can recommend. No more thin or one tooth short errors, works good. The article used two switches as inputs, where as I and I"m sure others have done, used a 4 x 4 key pad. Not being very well versed in micro electronics I received help from readers on this forum, and from my neighbour Steve, many thanks fella"s. John

Unless you have a CNC machine or stepper driven rotary table, a manual rotary table is one of the few ways to machine cylindrical paths in a way you couldn"t otherwise. You"d struggle to do that with a dividing head. I used my rotab to machine internal and external surfaces with success, although nowadays my CNC machine does a much better job in a fraction of the time.

I have seen a Rotary Table with dividing plates at a good price, what are the advantages of a Dividing Head over the Rotary Table. I know that a chuck can be fitted to the Rotary Table, it seems to me they do the same job.

They are similar devices with similar functionality. But I"d say a Rotary Table is generally more flexible than a Dividing Head. Often a table can be mounted either flat or vertically, whereas heads are typically one-way. It"s occasionally useful to be able to clamp work direct to a table. Heads often only divide while tables usually do angles and divisions.

I have a rotary table, and combined with a calculator can divide any number of divisions, not limited by the plates. BUT it"s even easier to get wrong if not systematic.

My Vertex HV6 is one such. It cost me three scrap items, before realising that the errors were not mine. I made up my own division table, using EXCEL. This showed that the published table had eight errors or omissions!

Thanks for these replies they have been very informative. The reply from Dave Halford about cutting curves on the Rotary Table can be a problem with the worm gear, if not up to it.

I have been given a 4 inch table some time ago unused which was purchased in the mid eighties. It is a import and will cut a curve in steel as I used this to recess a flywheel.

I like the idea of a Rotary Table with plates, the ones I"ve seen advertised by Warco seem quite a good price, but are they any good,can they cut curves in steel with out stripping the worm gear ? Fed up with buying crap, stuff not fit for purpose until modified.

This is what can happen to the gears when cutting a curve if the load is too high. The rotary table was not one of the cheap ones but a quality one, made in Japan.

A rotary table is a handy accessory for your mill for lots of applications.and I would not be without one but would advise that you get the biggest that would fit on your mill table..

I have happily cut curves in mild steel and gauge plate on my Soba 6" but they were within a reasonable expectation of what the table could handle and the depth of cut was also appropriate to my machine and tooling. Take a look back through some of Paul"s other photos and see the size of work being done on his similarly made but "quality labled" table and is it any wonder the gears stripped?

Chain drilling followed by light finishing cuts with a keen cutter may be a sensible alternative to trying to make heavy cuts with less than keen cutters (and not climb milling, either), when using a less robustly built rotary table. So, much in agreement with JB, I suppose.

Apologies to Howard if this is well covered elsewhere, but the calcualation to *check* an entry in a division table is relatively simple. It does involve vulgar fractions. Do schools still teach that?

Whatever about the rotary tables themselves being crap and way out,there is no excuse for the charts to be in error. A simple test run would soon show up any blunders which should then be corrected before production.

If anyone wants to try amending the original spreadsheet for gear ratios other than the original 90:1, the EXCEL spreadsheet is viewable at the top of the thread quoted by Neil. Hopefully, changing the formula from 90:1 to, say, 40:1 will produce sensible answers for Rotary Table or Dividing head with that ratio.

Am wondering if I am clever or brave enough to make two more division plates for my HV6. A "D" plate with 22, 24, 26, 28, 32,34, 38 holes and an "E" plate with 42 and 46 holes. All these should be "doable" with the existing "A", "B" and "C" plates, and would fill a few gaps in the table.

Another project would be to make a small Dividing Head for the mini lathe, (inspired by Stub Mandrel"s one, using the division plates from the HV6. Another "Make it up as you go along job"!

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Grab one at a used bookstore -- or an eBay auction. I would say that for a non-CNC hobby metalworker, anything from about the 15th edition on would be quite useful -- though if you want specs of standard collets, you need the 25th edition or later.

Thicker plates (to keep the holes from going through and interfering with each other) and fewer plates needed for the a given division ratio of the gears.

And whether the holes are countersunk or counterbored. IIRC, the B&S ones are counterbored, and fairly thick plates which can be mounted from either side, though you have the same number of holes on each side.

However -- if you get a plan which specifies angles in degrees minutes and seconds, you"ll have to deal with it -- at least long enough to convert it to decimal degrees. (This is where having an old HP 15C scientific calculator is nice. It includes keys which will convert either way -- useful for both time and angles.

Actually -- a CNC computer is running at a rather dumb level, so you are probably better than it. It is just more patient at following precise directions -- which *you* need to give it -- or a program (or set of programs) on another computer needs to give it.

Hmm ... if it is reading the absolute angle in binary, it would need at least 19 circles of encoding bars, which would make it fairly large. For reading it incrementally, you would need a single circle with 360000 bars, plus a single index indicator hole.

360 degrees. The backlash in the worm, and perhaps eccentricity of the wheel could introduce a lot more error than that. You really want to measure the angle at the rim of the table, which means that you would need a scale wrapped around the rim of the table, and given the resolution of the typical digital calipers (ignoring the 0.0005" step), you would need a scale 360" long, or a table with a diameter of 114.59 inches, or 9.5493 feet.

That"s what the worm gear and the plates are used for. You look up in the table the number of teeth (divisions), it will suggest one or more circles (so you may not have to change discs), how many full turns plus how many holes to move from one to the next, and the angle to set the arms to so they will guide you to the right hole. Then you shift the pair of arms so the starting arm comes to rest against the pin were the finish arm was at the end of your previous cranking.

Note that you did not have to know either degrees and decimal fraction, or the degrees, minutes and seconds. All you needed to know was the number of teeth or divisions you needed to make, and where to find the lookup table (either in Machinery"s handbook, or on a metal plate which came with your dividing head when new.

However -- cranking in degrees and decimal fraction or degrees and minutes (I don"t think that seconds are marked on the dial on a rotary table) does lead to accumulated error by the time you finish your circle.

Be warned that some numbers of divisions are very difficult on a dividing head (unless you go to a differential head perhaps). 127 teeth is an example of that which is important to lathe users.

Very much so. With a 90:1 ratio, you use a single hole on any circle of the plate, and crank the table through 15 turns of the crank and end up back at the same hole.