# Rotary table



## mf294-4 (Mar 22, 2020)

Need a vertical rotary table with index capabilities. Looking at the Grizzly T25937. Anyone use this or have any alternate sujjestions. Just a home shop not used very often.


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## LEEQ (Mar 22, 2020)

I like my little 6" grizzly vertical horizontal rotary table. It has dividing capability and plates came with it. That's not exactly indexing though. Not as fast and easy as indexing. I settled on it as the solution to as many shop problems as I could squeeze into one tool. I think quick indexing is the biggest compromise made by going that route.


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## machPete99 (Mar 23, 2020)

I am curious as to the difference between using dividing plates on a rotary table versus "indexing". Would you care to elaborate? I am also considering a RT in the near future... tx!


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## C-Bag (Mar 23, 2020)

My take on it is indexing like with a spindex is all done simply with holes and a pin and achieves 1deg accuracy where rotary tables with plates achieve minute and second accuracy. A spindex is a very cheap handy tool for simple quick work if you are not doing large complicated work and only need 1deg accuracy.


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## Lo-Fi (Mar 23, 2020)

It's all indexing, just different types. 

A series of holes or notches around a rotatable fixture is called "direct indexing". A handle geared to the rotating fixture with a plate with holes in or similar is "simple indexing". Lots of dividing heads have direct indexing options - quite often 24 divisions - as well as the geared handle and plates for simple indexing.


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## Winegrower (Mar 23, 2020)

The difference in accuracy is all in favor of the geared dividing head.   On mine, there is a 40 to 1 gear reduction, so any error because of pin placement is reduced by the same factor of 40.   The spin indexer, you get whatever pin error or slop exists coupled directly into your part.

I have both a spin indexer and a dividing head.   I made a tilt table, first with the indexer to cut reference flats, but I was not satisfied with the result and had to recut with the dividing head, which came out spot on, measured against angle gauges and dial indicator.


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## RJSakowski (Mar 23, 2020)

There seems to be some confusion over the distinction between resolution and accuracy.  Resolution is the finest increment that you are able to resolve.  i.e., a spin indexer with 360 discrete positions has a one degree resolution.  There is no way that you can set a 15.5º angle.  However, a 15º angle would be 15º +/-4' (.07º) from the Shars spin indexer specification.

The biggest difference between an indexer and  a rotary table is that the rotary table allows moving to any angle within the limits of the RT resolution.  An indexer has to work with the available divisions.  It works well in making bolt circles with a set number of holes. You cannot set a 13º57'23" angle with it

OTOH, my RT has a 90:1 gearing and is able to resolve 5" (.0013º).  If I wanted to make a 127 tooth gear with the RT, I could by incrementing my position by 2º50'5". (To minimize  errors and prevent error stacking, I would use an Excel spreadsheet to calculate the settings).  It would be more cumbersome than  using an indexer but it will get the job done.

In an ideal world, I would have both but faced with the choice of an indexer or an RT, my choice would be the RT, simply because it is more versatile.


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## benmychree (Mar 23, 2020)

If one has a universal dividing head, where the spindle is geared back to the dividing plate through change gears, prime numbers such as 127 can be divided exactly with no stacking errors or spreadsheets, this I did to make metric transposing gears for my lathe and automatic gear cutter.


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## Janderso (Mar 23, 2020)

benmychree said:


> If one has a universal dividing head, where the spindle is geared back to the dividing plate through change gears, prime numbers such as 127 can be divided exactly with no stacking errors or spreadsheets, this I did to make metric transposing gears for my lathe and automatic gear cutter.


That is so complicated, I put that procedure right up there with rocket science.


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## benmychree (Mar 23, 2020)

It is not as complicated as it sounds, no calcs to do, its all in the book ----


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## projectnut (Mar 23, 2020)

Here's an example of a horizontal only rotary table/indexer.  This one is not mine.  Mine doesn't have the indexing option. :





I'm not sure if anyone today still makes this type of table.  I've never seen one that can be used both horizontally and vertically.  I can bolt mine to a 15" angle plate, but it's all but impossible to move around.  The indexer weighs around 250 lbs. and the angle plate weighs another 150 lbs.


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## benmychree (Mar 23, 2020)

That looks like a nice one, who made it?


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## middle.road (Mar 23, 2020)

benmychree said:


> It is not as complicated as it sounds, no calcs to do, its all in the book ----


There's a 'book'?


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## benmychree (Mar 23, 2020)

middle.road said:


> There's a 'book'?


Yes, there is a book!  "A practical Treatise on Milling and Milling Machines" by Brown & Sharpe, I got mine when I apprenticed back in '64, it was one of our textbooks in class.  It contains a lot of good information, including the setup for differential indexing that I posted above; some info is specific to B&S machines, but a lot of it is applicable to other manufacturers.  Cincinnati also published a similar book, larger and more technical.


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## projectnut (Mar 23, 2020)

The one in the picture and mine are both from the Index Machine Tool Company.  The company was started in 1938 and sold to the Wells Machine Tool Company around 1971.  According to their sales brochures Wells-Index is today the only vertical milling machine company to build and assemble all components in the USA.

I paid about $25.00 more than the one Mr Whoopee saw in the ad:









						Brown & Sharpe positioner - $125 (Kelseyville, CA)
					

https://mendocino.craigslist.org/tls/d/kelseyville-brown-sharpe-positioner/7095634085.html




					www.hobby-machinist.com
				




But I think mine has at least $25.00 more metal in it.


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## Mitch Alsup (Mar 23, 2020)

I have a 10" horizontal only rotary table. I used to have my 4" vise mounted on its own rotation table, but I like the rotary table so much, I ditched the rotating base and mount the vise (semi-permanently) on the RT. This makes tramming way easier. A 10" table is probably one of the stronger links in the stiffness of my G0730 Mill. The 10" table is also just at the limit of what I can bend over and pick up.

As to horizontal capability, the 5" table you selected seems adequate, I, personally, would have been looking at a 6". But we are in the same ball park.

Indexing capability merely allows one to place a series of machining operations around a circle without looking at numbers. A RT without indexer can do everything a table with indexer can do, but you have to have more precision in your application of the dials--and never forget always approach the final dial setting from the same direction.


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## Lo-Fi (Mar 23, 2020)

Janderso said:


> That is so complicated, I put that procedure right up there with rocket science.



Charts make it look like black magic, but the math is fairly simple. I have a dividing head with this capability and have cut some gears using differential dividing. It's quite fun! Rather than using charts, I coded myself a windows app to do all the calcs. The results are interesting, picking up some possible dividing solutions - both simple and differential - that don't appear in charts when there's more than one solution. I've also successfully tried a spreadsheet. Now I've got time on my hands, I'll finish tidying it all up to release it!


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## talvare (Mar 23, 2020)

RJSakowski said:


> In an ideal world, I would have both but faced with the choice of an indexer or an RT, my choice would be the RT, simply because it is more versatile.



I made the same choice about 8 years ago but still wanted the ability to index with the hole plates as you would with a dividing head. I found a nice used 10" horizontal/vertical rotary table on eBay and then determined what plates I needed for it. It didn't take too long before I found a used set on eBay that would work well with my 120:1 rotary table. Then I made the other required hardware, eg; sector arms, crank, locating pin, etc. I don't use it often, but it works very well when I do.

Ted


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## Shootymacshootface (Mar 23, 2020)

Joe Pi has an awesome vid about rotabs. I think he used a Phase ll. It has a vernier type scale on the handle, I believe that you can set it to 100ths of a degree. He is a master at using a rotab. 
I believe that I have the same one that he used, a 10" Phase ll vertical only. I made a jumbo angle plate so that I can use it horizontally.


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## middle.road (Mar 23, 2020)

benmychree said:


> Yes, there is a book!  "A practical Treatise on Milling and Milling Machines" by Brown & Sharpe, I got mine when I apprenticed back in '64, it was one of our textbooks in class.  It contains a lot of good information, including the setup for differential indexing that I posted above; some info is specific to B&S machines, but a lot of it is applicable to other manufacturers.  Cincinnati also published a similar book, larger and more technical.


Man, how I wish there were still apprenticeships around when I got into the workforce in the late '70s. 
The Gent that hired me as a draftsman in the toolroom told me that it was sad that 'apprenticeships' were no longer around but if I paid attention and listened I could learn quite a lot.
(40) years on, I wish that I'd paid better attention and listened. . . Little did I know.


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## Silverbullet (Mar 24, 2020)

projectnut said:


> Here's an example of a horizontal only rotary table/indexer.  This one is not mine.  Mine doesn't have the indexing option. :
> 
> View attachment 317868
> 
> ...


But it will get the job done - the mill tips over falls from the weight if you listen to us old guys. With an adjustable angle plate imagine the uses. Truthfully its the way i had planned to go.


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## brino (Mar 24, 2020)

mf294-4 said:


> Need a vertical rotary table with index capabilities.



I have two pieces of advice....(without trying to spend too much of your money   )
1) consider a combination vertical and horizontal rotary table, it really adds possibilities to what you can do in your shop and how easily, and
2) go as big as you can, when you start bolting things down to the table it starts looking much smaller.

Of course, so much depends on what you are building and the size of your machines.
If you are only ever going to do small shafts and things that can fit in a 3-4inch chuck, then perhaps a 5" RT is big enough.
But it you ever want to bolt your milling vise down to it, or a large plate to round the corners, then bigger is better.

example, I used mine to carefully and slowly mill down a faceplate that was too big diameter for my lathe, but had the proper spindle thread.

-brino

EDIT......I was going to come back and add #3) get a matching tailstock, but I see your suggested Grizzly T25937 has both #1) and #3 covered. So I guess it's just down to size.


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## Tim9 (Mar 24, 2020)

I’ve read these sort of threads before. And although I agree a 10” table is nice for its size capabilities..... I would never make the mistake of buying a 10” table again. Damned thing is too heavy. Most of the time....I’m just needing to do a minor job connected to a larger project. 
   I look down at that beast of a 10” rotary table....and find a work around. I wish I would have purchased an 8” table.


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## brino (Mar 24, 2020)

Tim9 said:


> I look down at that beast of a 10” rotary table....and find a work around. I wish I would have purchased an 8” table.



I bet you could find someone willing to swap.
(...especially if you cover shipping  )
-brino


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## Tim9 (Mar 24, 2020)

Maybe someday when I start to thin my tool collection I put it up for sale. But yes, I agree it’s nice to have that capability of a 10” table.
   At the same time, if I were to do it now whith what I know now... I’d get an 8” and make a 10” or 12” plate to attach to the 8” rotary table for those rare times I need the extra table space.


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## RJSakowski (Mar 24, 2020)

My 12" RT is pretty much a permanent fixture on my mill/drill.  It hasn't been off for more than a decade. For most work, there is enough room for a vise on top and it is large enough that my 4" machinists vise can be mounted.  For those jobs where I need more z height, there is the Tormach.
In contrast, I have a 6" 4th axis RT for the Tormach but it has only been on the machine a few times in the past eight years. It is heavy enough to not want to lift it on and off and it takes up too much table space to leave it on.  There is no real reason to use a horizontal RT on a CNC mill and when used in a vertical orientation, it needs to be squared up to the table to be useful which is too much bother.  But it is there if/when I ever need it.


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## RJSakowski (Mar 25, 2020)

Before I got my CNC mill, I was thinking about ways to cut curves on a mill.  The thought that came to mind was to mount an auxiliary x-y table on the RT.  

A RT is great for cutting arcs but the arc has to be centered on the rotational axis of the RT. With an x-y table on the RT the work can be positioned so that each arc was concentric with the RT axis.  The calculations can get a bit hairy but with the use of a CAD package and/or an Excel spreadsheet,, it's manageable.  

This strategy is essentially how a CNC machine cuts complex curves.  Rather than using a G01 straight line move, G02 or G03 moves by arc are used. The difference being that the CAM processor does all the complex math calculations to translate and/or rotate the coordinate system.

Around twenty years ago, I ran through the exercise for an Archimedean spiral (the same curve found in many seashells).  At the time, I was looking at having a spiral cut in a piece of plate by wire EDM but the machine could only accept 100 blocks of code. In order to maintain the accuracy of the cut path to .01mm, it took thousands of moves by straight line interpolation.  By moving by arc, the number of moves was reduced to 24.


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## projectnut (Mar 25, 2020)

benmychree said:


> That looks like a nice one, who made it?





Tim9 said:


> I’ve read these sort of threads before. And although I agree a 10” table is nice for its size capabilities..... I would never make the mistake of buying a 10” table again. Damned thing is too heavy. Most of the time....I’m just needing to do a minor job connected to a larger project.
> I look down at that beast of a 10” rotary table....and find a work around. I wish I would have purchased an 8” table.



I wouldn't be to quick to get rid of your 10" rotary table.  I've had an 8" one for several years.  It's light enough to pick up and carry to the mill. but it can't handle all that much weight.  The smaller ones use plain bearings (bushings) rather than ball or roller bearings.  It's tough to turn a 2" hand wheel to rotate a 150 lb. casting.  The weight and the friction of the bushings makes it feel like you could easily twist off the hand wheel, or snap the screw.

Last year I purchased a 12" Index brand rotary table for the larger jobs.  It isn't something you're going to carry around in one hand, but it does handle the big stuff much easier, and is far more stable.  I move it with either an overhead hoist like this:






						Strongway Electric Cable Hoist  750-Lb. Single Line Capacity, 1500-Lb. Double Line Capacity, 38ft./19ft. Lift | Northern Tool
					

This Strongway Electric Cable Hoist is a rugged, efficient 120V/60 Hz hoist that makes lifting easy. It lifts loads up to 38ft. at speeds...




					www.northerntool.com
				




or a hydraulic table like this:









						1000 lb. Capacity Hydraulic Table Cart
					

Amazing deals on this 1000Lb Hydraulic Table Cart at Harbor Freight. Quality tools & low prices.




					www.harborfreight.com


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