# Rotary Table Questions



## FanMan (Jul 21, 2016)

I've put it off for a couple of years, now I have an imminent project to justify buying a rotary table.  I'm figuring on a 6" one because anything larger would seem to be too much for my Jet 15 mill/drill.  Don't want no name cheapo ($150), can't spend big bucks, Phase II and Vertex seem right, and from what I've heard the Vertex sounds like the way to go.  I'm looking at this one on ebay.  It's billed as "Accura/Vertex.  I asked, and the seller says, "*It is from the VERTEX factory in Taiwan*... it is a VERTEX product we sell and own ACCURA but source these from VERTEX."  So presumably it's like many others; one manufacturer and many different name plates depending on who's selling it.

I don't need a chuck or dividing plates, I want it mainly to cut curves and such (I can XY any bolt circles).  I don't own a lathe, I turn small short parts in the mill, with a rotab I can make larger round parts and larger holes in any workpiece small enough to clear the column as I rotate it.

Newbie question:  Like most rotabs, it has a MT2 center hole. , so how do you use the center hole?  Can I get a MT2 plug to go in the hole with a projecting cylindrical button that I can use to center my work?  Or is that the wrong approach?


----------



## dlane (Jul 21, 2016)

I got a 8" vertex , has a mt3 center , I cut  the mt3 j33end off and bored a 3/8" reemed hole for a 3/8" dowell , I also added a fixture plate that centers on the mt3 stub , also made plug that is a snug fit in spare lathe chuck with a reemed 3/8" hole in center for locating Chuck  then bolted down to plate





The few times I've used it works good.


----------



## Bob Korves (Jul 21, 2016)

I did much the same as Derrick did, but left the JT taper on the arbor.  I use the factory arbor center hole at the end of the JT taper to center the rotab.  I put a pin with an accurately centered 60 degree point in a collet, install the MT adapter in the rotab, and then run the quill down to engage the 60 degree center hole in the arbor center.  Lock the spindle when the two centers are pressed snugly together and then tighten the rotab to the mill table..  That is the quick and dirty method, and is accurate enough for most work.  For more accurate work, center the JT taper by swinging a dial test indicator mounted in a collet around it and dial it in.  The other beauty of leaving the JT taper attached is that the shoulder under the JT taper gives you an easy way to extract the MT taper from the rotab while it is mounted to the table, using a small pry bar.


----------



## FanMan (Jul 21, 2016)

Thanks guys.  So I guess this or similar is all I need.


----------



## chips&more (Jul 21, 2016)

Not trying to be the monkey wrench…but. I have a RT. Had it for maybe 40 years. Can’t say I can recall ever using it? Guess it’s because the darn thing is soooo heavy and I don’t get the enjoyment as I do from other set-ups. Don’t get me wrong, I make arcs and such, but you can be inventive and find other ways…Dave


----------



## FanMan (Jul 22, 2016)

Dave, if you can tell me how to cut an _accurate _4.5" diameter and a slightly smaller diameter trepanned groove in a 1/4" plate without a rotary table (or CNC or a lathe), I'm all ears.


----------



## chips&more (Jul 22, 2016)

Don’t know all your details? A boring head comes to mind. NOTE: when using a boring head, check the construction/connection of arbor to head. If it’s threaded, make sure it will not unscrew if using the boring head in a other than normal operation.


----------



## FanMan (Jul 22, 2016)

Hmmm, yes, a boring head (which I don't have either) could do it.  I'd need reversed cutters, since my mill isn't reversible.  But for this project and some others I think the rotab (which I ordered this morning) is the way to go.


----------



## RJSakowski (Jul 22, 2016)

How would you cut a 90º arc?


----------



## JR49 (Jul 22, 2016)

chips&more said:


> Not trying to be the monkey wrench…but. I have a RT. Had it for maybe 40 years. Can’t say I can recall ever using it? Guess it’s because the darn thing is soooo heavy and I don’t get the enjoyment as I do from other set-ups. Don’t get me wrong, I make arcs and such, but you can be inventive and find other ways…Dave





RJSakowski said:


> How would you cut a 90º arc?



I too would love to hear some examples of how you, Dave, or anyone gets around using a RT.  Not trying to challenge,  just trying to learn.  Thanks,  JR49


----------



## Bob Korves (Jul 22, 2016)

FanMan said:


> Thanks guys.  So I guess this or similar is all I need.


It works for me.

Edit:  Try to look at it first, before buying, to make sure there is a recess between the MT and the JT so you can pry it out of the rotab.


----------



## minions (Jul 23, 2016)

RJSakowski said:


> How would you cut a 90º arc?








?


----------



## ScrapMetal (Jul 23, 2016)

minions said:


> ?



Well, I've use that technique for some small "down and dirty" stuff but it's not the most precise method.  Using larger arcs is not even practical let alone doing an inside arc or slotted groove.  I found the RT to be invaluable for doing work like this...




JMHO

-Ron


----------



## cathead (Jul 23, 2016)

Before I got my rotary table, I made a repeatable jig mounted in a Kurt vise with a rotary base.  The center was carefully located with a pin 
so sheet material could be clamped to the jig.  Then it was a simple matter to position the cutter for the diameter and rotate the
vise to mill.    It works great for making discs or grooves as mentioned above.


----------



## RJSakowski (Jul 24, 2016)

Most internal arcs can be cut with a boring tool. 

The video presumes that you have a central hole for the axle which is not always true.  Putting a 2" fillet on a n 8" x 8" workpiece would be difficult.  Cutting an arced slot would not be possible.  

Before I got my RT, I cut arced slots for a product we made with a custom jig, using lead screw to rotate the part but is was not conducive to general use.  The DRO on my old mill has a program for cutting arcs by a step and cut method.  You could specify the deviation from the true surface which determined how many cuts needed to be made.  I usually settled on something like twenty to fifty steps.  The process was tedious and slow and prone to errors if you didn't pay attention to the order of operations.  You could also cut an arc by a series of intersecting plunge cuts with an end mill.  With a little care, you could get an arc that required very little hand work.


----------



## FanMan (Jul 24, 2016)

I've used some of the above techniques (swivel vise, pivoting on a pin, nibbling and filling) before,  but this job (a propeller crush plate and spinner mount for my plane) requires a higher level of accuracy.


----------



## LARRY BOYD (Sep 13, 2016)

Sure have to agree with everyone on value of a RT.I bought a 16 inch used one for $100. a few years ago.I had it on my mill once.Takes at least two big men to handle it.About five yrs.ago I bought my lathe from a fellow in Portland Or.When I went to pick it up he asked if I needed any other equip? I bought a 12in.Bridgeport RT for $200. Two people can handle it with no problem.Right place at right time.


----------



## Tony Wells (Sep 14, 2016)

I have a 6" Yuasa and a 16" Cinci......Even though I have a mill to match the Cinci, guess which one gets used most. I can pick up the Yuasa with one hand. The Cinci, not so. Not so with 2 hands. It requires a 2 wheeler and a hoist. Guessing around 300#.


----------



## toolroom (Sep 14, 2016)

Myself, being in the market for a decent 6" table... I would like to ask the members, which ratio works best. 90:1  72:1 ?


----------



## JimDawson (Sep 14, 2016)

Both of mine are 90:1, seem to work fine. Most larger tables are 90:1.  The only advantage of a 90:1 over 72:1 that I can think of might be a slightly finer adjustment capability.


----------

