Confused ….Advice needed rotary table vs dividing head

[Me.Participant @me1]

Is a rotary table the same as a dividing head – can a rotary table be converted to be used as a dividing head, and if so is just a case of getting the plates.

[Me.Participant @me1]

[HollowpointParticipant @hollowpoint]

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

[Brian GParticipant @briang]

I have a very small rotary table and considered making up a set of division plates and indexing mechanism for it, but found it easier, quicker and cheaper just to add a stepper motor and controller Following the step-by-step (sorry) instructions on HMEM was my first introduction to Arduinos., and there is a similar project in MEW 249.

I will admit however, that I am still tempted to use the stepper driven rotary table to make a set of division plates just because I could.

Brian G

[SillyOldDufferModerator @sillyoldduffer]

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

[Frances IoMParticipant @francesiom58905]

can some mod please change the title to something relevant that will aid future searches – quite why we are seeing such a plethora of weird titles defeats me unless Covid has unknown side effects

Edited By Frances IoM on 14/02/2021 16:03:47

[JasonBModerator @jasonb]

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.

[Stuart BridgerParticipant @stuartbridger82290]

Good overview here Link

[Howard LewisParticipant @howardlewis46836]

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

[old martParticipant @oldmart]

If you want to choose between one or the other, the rotary table can be set at any angle, but a dividing head cannot. The rotary table is more versatile, so make that your first choice.

[Martin KyteParticipant @martinkyte99762]

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

[Me.Participant @me1]

Posted by old mart on 14/02/2021 18:13:12:

If you want to choose between one or the other, the rotary table can be set at any angle, but a dividing head cannot. The rotary table is more versatile, so make that your first choice.

Thanks everyone for the complete and comprehensive replies – I will look out for a rotary table that will work with my Mill.

Sorry about the original title – I didn't realise it would make things confusing for others.

[old martParticipant @oldmart]

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.

[Me.Participant @me1]

Posted by Frances IoM on 14/02/2021 16:03:27:
can some mod please change the title to something relevant that will aid future searches – quite why we are seeing such a plethora of weird titles defeats me unless Covid has unknown side effects

Edited By Frances IoM on 14/02/2021 16:03:47

It has been scientifically proven that the more obscure a thread title the more views it will get — curiosity is a wonderful thing.

It made you look ……

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Me. on 15/02/2021 08:51:11:

Posted by Frances IoM on 14/02/2021 16:03:27:
can some mod please change the title to something relevant that will aid future searches – quite why we are seeing such a plethora of weird titles defeats me unless Covid has unknown side effects

Edited By Frances IoM on 14/02/2021 16:03:47

It has been scientifically proven that the more obscure a thread title the more views it will get — curiosity is a wonderful thing.

It made you look ……

.

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.

[JasonBModerator @jasonb]

Posted by Michael Gilligan on 15/02/2021 08:59:45:

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

 

 

At least the new forum software will be more traceable and have far better search functions which should please you.

I expect the rest of us are working to the OP's opening post which set out his question, heading was just rather vague much like people who just put "help" as a title.

 

Edited By JasonB on 15/02/2021 10:03:05

[Michael GilliganParticipant @michaelgilligan61133]

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.

[Me.Participant @me1]

As it was "I" that started this thread with the now "banned" snappy title of "Confused DOT com, whats the difference between."…… I must apologies profusely for my shameful woful excuse of a title.

I will have to think of less intriguing titles for my threads.

Science is a wonderful thing – some claims have more fact that fiction – scientific theories claimed by the uninformed are sometimes false….. IYKWIM.

For those interested – I am looking for a rotary table – it seems to be the best beginner option.

[Michael GilliganParticipant @michaelgilligan61133]

[ChrisHParticipant @chrish]

Not really the thread to ask this, going off subject, I do apologise in advance, but as Jason mentioned the new forum software, could Jason say whether it will have posts numbered for easy reference please?

Just wondering!

Chris

[JasonBModerator @jasonb]

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.

[BazyleParticipant @bazyle]

Bit like the infuriating "Newbie…" and "Please be gentle….".
As this is an engineerig forum I hope a proper Change Request was submitted, signed off by the Material Review Board, approved by the Quality Manager et al, carried out and documented on an Alteration Note and recorded on the Maser Record Index before launching the revised issue thread. BTW is this thread at letter issue status for development or has it been raised to number issue for production yet?

[Oily RagParticipant @oilyrag]

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

[Nigel McBurney 1Participant @nigelmcburney1]

lots of statements,regarding dividing heads,and some are not entirley true. Comparing a rotary table to a dividing heads is ok but a rotary table with dividing plates or stepping drive can only be compared to a universal dividing head which has a full set of gears which increases the dividing range,carry out helical cutting for gears and threads . Spirals can be cut in a face ,silmilar to the scroll of a 3 jaw chuck,plus cams for auto lathes.I have dividing heads and rotary tables,though the most ffequently used indexing tool is a Marlco twenty four position indexer which is meant to be used with the chuck vertical though it can be used horizontally with an angle plate,24 positions allows indexing of 2,4,6,8,12,24 divisions there is an outer ring divided in degrees.An industrial quality device fitted with a 5 inch Burnerd chuck and an adapter plate to take a 5c collet chuck. Great for making brass fittings with hex features,old style whit nuts and bolts and lots of othe items which require indexing to a good quality but not quite to the precision of a good dividing head,and its quicker to set up and use plus it allows the dividing head to be only used for precise work thus reducing wear and maintaining accuracy.

[Anonymous]

Posted by Oily Rag on 15/02/2021 13:58:24:

Also how do you produce a bevel gear on an RT that will only align to H or V?

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

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