No, not the same. Though they both do similar jobs. Some rotary tables can be converted to dividing heads.

I'll have a go at the differences! Feel free to put the mistakes right.

Rotary tables are mounted horizontally, and most can also be mounted vertically. In both cases only at 90° to the mill table. A Dividing Head is always vertical, but can be tilted through 90°.

Dividing heads are always fitted with 'indexing plates' (holed wheels and clock hands), allowing a wide range of angles to be turned. The indexing mechanism can do intermediate angles. Rotary tables can be fitted with indexing plates as an accessory, but usually the number of angles supported is limited compared to a dividing head. (A generalisation. And, because rotary tables do all common angles, the limitation may not matter.)

Dividing heads are likely to be more accurately made and expensive than a rotary table. Extra accuracy costs money.

Rotary tables are more convenient for general work because most jobs are mounted at 90° or 180° relative to the milling table. Possibly more robust than a dividing head for rough work. When close accuracy isn't needed, jobs can be spun rapidly by the rotary table without cranking the handle – a time saver. When accuracy is needed the handle and worm are engaged. Usually there's a vernier scale sufficiently accurate for most work. The handle is also relatively fast because most simple angles can be produced with it. For example, easy to crank from 0, 60, 120, 180, 240, 300, 0 to cut a hexagon head. Unfortunately not all angles are 'simple'!

Indexing plates are useful for awkward angles. Cutting a 19 toothed gear requires 19 steps of 18.9474°, which is the hard to remember sequence 37.89, 56.84, 75.78, 94.74, 113.68, 132.63° etc. The Index plate and clock hand mechanism remove the need for the operator to track the sequence but they are still a pain to use in my opinion!

Indexing plates are so awkward that driving a Rotary Table with a stepper motor and microcontroller is popular. You simply tell the controller how many divisions are needed, press 'Go', and the computer does the rest. Apart from reducing brain strain and automating a tedious task, the computer eliminates most mistakes. Computers don't get sums wrong, have excellent memories, and are hard to distract! Also, a computer and stepper motor will do a good job of angles too complicated for the Indexing plates.

Generalising again, I suggest most people, most of the time, only need a rotary table. I see Dividing Heads as specialist tools and have never felt the need for one. For the same reason I drive an ordinary small car rather than a Land Rover. The closest I get to off-road driving is a supermarket car park! You might live on a farm…

Unless there's a specific reason for needing a Dividing Head, I wouldn't spend money on one. My rotary table is used a lot, in contrast a Dividing Head is only 'nice to have'.

Dave

Edited By SillyOldDuffer on 14/02/2021 15:56:21

The main difference between the two is that a rotary table lets you rotate the work so radial or axial cuts can be made but a dividing head is just moved in increments. Therfore only the rotary table can be used for curved work.

I have a Rotary Table (a Vertex HV6 with a 90:1 ratio ) It is most often set with the face vertical, and at 90 degrees across the table.( Axially along the table, if you follow me ) In this position, and with the aid Division Plates, and a Tailstock it is used to cut gears .

It could equally well be used in this way to mill splines or to drill holes around the periphery of a workpiece, with what ever angular spacing required.

So in that respect it has operated as a Dividing Head.

With the face horizontal, it has been used to mill curved slots, and could be used equally well to put a radius on the end of a workpiece.

HTH

Howard

My penny's worth.

Rotary tables are for moving a workpiece in an arc around a centre for machining purposes.

Dividing heads are for setting a workpiece to a specific angular orientation and fixing it there whilst a machining operation is carried out.

As such rotary tables may allow some degree of indexing and dividing heads may allow for some degree of rotation which is were the confusion comes in.

regards Martin

The last time I used the rotary table was to mill 7 splines. I didn't even look at the dividing plates for the rotary table, 51*26' was close enough for government work.

.

Having come late to this thread, I have to ask :

Are we now working to the original title, or the new improved one ?

… as is typical on this forum; there is no audit trail

MichaelG.

Thanks for the info. Jason … although it doesn’t answer the question that I asked.

What was the original title ?

If it was ‘Confused’ then I would agree entirely with the point made by Frances

… and the fact that I was not attracted to read on, might count against the OP’s scientific claim.

MichaelG.

As far as I can see you can copy the link of a specific post which will take you back to that post rather than the top of the thread page. No numbers on RCM&E but that may not have been enabled.

I have some concerns with the statements that have been made above concerning DH's versus RT's.

Since when has a DH not allowed the free form production of a radial surface or a slot? (Jason) When a DH will swing through -15degrees up to vertical and beyond (again by a further 15 degrees), this is despite attachments to the mill which allow a inclined table. The handle can be rotated with the plunger in the 'park' position and radial slots and surfaces can be produced.

How does a stepper controlled RT deal with step 'dead bands', also the step position is accurate only within the range of the step feedback or encoder resolution, or even the electronics bit conversion function. Analogue is infinitely more accurate than digital (SOD – Computers don't get sums wrong – 'altogether now' – Oh yes they do! Try dividing 10 by 3 and then multiplying the answer by the original divisor – guarantee you won't get 10 as an answer). Also how do steppers deal with backlash? Do they 'dither' in the same way as a Moog valve?

Using a RT as a DH for producing such items as splines or gears is problematic in that the cutter is liable to foul the table, unless the component is hanging a long way out from the table, that requires a tailstock to support the overhang. Also how do you produce a bevel gear on an RT that will only align to H or V? – answers on a postcard please. All my RT's are only designed to be used horizontally, they are designed for that purpose. My DH's are all designed as either simple indexers, universal indexers or compound indexers. The later can be driven off the table drive for spiral milling or they can accommodate ANY division requirement by gearing the index plate to the head rotation; thus giving a compounded angularity by movement of the index plate reference point to the handle movement.

Sorry to ask these questions but there needs to be 'accuracy of statement' spoken to novices otherwise they will get 'fake news'! And that leads to 'Confusion'!

Edited By Oily Rag on 15/02/2021 14:01:45

Use a CNC mill:

Unlike with a dividing head and involute cutters the above method produces a true bevel gear.

Rotary tables and dividing heads are complementary, although there is overlap in use. The well equipped workshop has both.

Accuracy, precision and resolution are not the same thing, so one can't say that analogue is more accurate than digital or vice versa. It all depends.

It's been some years since I used Moog valves, but I don't recall them having dither? The ones I used were about the size of a small matchbox. We used them as part of a crash gearbox on a racing car. They were current driven, so I designed a voltage driven bi-directional current source to control the valve.

Andrew