Rotary table tricks and tips

[Holescreek]

There is more than one way to set equipment up for use and we all have our favorites. The rotary table is no exception. Hopefully all of the setup ideas can be lumped into a single thread so none of them will get lost in the fray.

Rotary tables of any size are heavy and we all tend to put off setting them up because of the hassle of clearing the mill table (removing the vise) and getting the rotary table mounted and trammed. In my case setting the vise back up and tramming it in afterwards was just as much hassle so I figured out another way. I had a bar of rusty 4" x 1.5" S7 standing in the corner so I decided to make a vise mount for my 9" Troyke table. I milled the rust scale off and ground the sides square.



The mount drops into my vise and closing the jaws locks it in place with the top level and square to the mill.





For the last 34 years I've been using an indicol with a top dial indicator mounted to it for most of my setup work. This setup makes it as easy to tram surfaces as it is to tram hole locations. You can also use it to locate edges precisely and measure radius sizes and locations without changing the indicator. Indicol is a brand name and there are generic indicator holders available that do exactly the same thing for way less money.



The indicol mounts to the mill spindle to rotate with the spindle. I use a 3" long chunk of scrap plastic between the clamp screw and the spindle to use as a handle for rotating the spindle but if I'm doing something precise I use the belts from the drive motor to rotate the spindle by hand and don't worry about influencing the indicator by accidentally moving the clamp on the spindle. There are a lot of moveable joints in the setup that allow you to precisely position the indicator. The next step is to move these around and get the indicator positioned until the ball on the indicator tip stays still as the spindle is rotated. in other words, the ball on the indicator tip becomes the center of the universe and everything else spins around it. Once centered, use the XY table handles to eyeball the indicator ball to the center of the hole you want to tram.



I always turn the rotary table so the contact points of the center hole are aligned with the table axis then push the stem of the indicol forward so the indicator tip touches the side of the hole to be trammed and set a zero on the indicator.



From there it's just a matter of rotating the spindle and positioning the table so that the indicator reads zero on all contact surfaces.

My last rotary table trick is just a plate I made for the top. I had a project where I needed to cut about a 4.5" radius on a large plate. The plate was too large to bolt to my 9" table so I bought some 1" thick aluminum, mounted it to the table and machined the outside diameter of the plate to 16". I used a small centerdrill to machine the setup lines in the top for future use. The drawback to the top plate is I have to drill and tap holes for clamps. The good thing is that I can use it for dedicated setups by only drilling and tapping holes one time.

 

[MADJACK]

Sweet, nice tips. Never thought about a vice mount!

 

[Holescreek]

I was kind of hoping members would add their own tips too!

 

[randyc]

Really like the vise mounting idea.

For centering the table, rather than sweeping the bore, I made a tight-fitting pin that fits the bore and sticks up from the table about two inches. With an R-8 collet in the mill spindle of the correct size for the pin, I shift the table around by tapping with a rubber mallet - or moving the table - until the pin slips into the collet.

This will usually center the rotary table within .005 and the location can then be refined with a DTI. Not necessarily an improvement, of course, just different, and in fact introduces a source of error, however slight.

My rotary table when stored, is on a corner of one of the work benches. I made a small plywood platform with casters and park the rotab on it. I can then roll it down the length of the table within four feet of either of the milling machines rather than lifting it and carrying it eleven feet.

 

[cathead]

Yes, I like the wheeled cart idea. My rotary table is heavy and at present I set it
on a stool along side the mill. Maybe a set of shopping cart wheels would
do the job under a cart of the proper height. Maybe that will be my next project.


QUOTE=randyc;272712]Really like the vise mounting idea.

For centering the table, rather than sweeping the bore, I made a tight-fitting pin that fits the bore and sticks up from the table about two inches. With an R-8 collet in the mill spindle of the correct size for the pin, I shift the table around by tapping with a rubber mallet - or moving the table - until the pin slips into the collet.

This will usually center the rotary table within .005 and the location can then be refined with a DTI. Not necessarily an improvement, of course, just different, and in fact introduces a source of error, however slight.

My rotary table when stored, is on a corner of one of the work benches. I made a small plywood platform with casters and park the rotab on it. I can then roll it down the length of the table within four feet of either of the milling machines rather than lifting it and carrying it eleven feet.[/QUOTE]

 

[randyc]

Making balls with a rotary table and a mill

With a rotary table and a mill, one can cut balls. I made a spread sheet for determining the setup for various diameters of balls. (This is the illustration on the spread sheet, there are calculations involved based on user inputs that are performed by Excel and are not shown in this sketch.) Generally, a boring tool is used to turn the balls with the cutting edge turned inward.



Horizontal mill with vertical head installed. The vertical mill must have been doing something else (this was done years ago).



And here’s the operation - I used a hole saw in this instance rather than a boring bar, thinking that it would be faster. Doesn't really matter what the configuration of the cutter happens to be if it's doing the same thing that a boring bar would be doing, LOL.




edited to fix misspelled word

 

[randyc]

Incidentally, there's a pretty cute trick in a thread below this one entitled "Centering A Rotary Table" that roughly centers a rotab.

 

[RJSakowski]

I have a 12" Enco horizontal/vertical rotary table which I keep mounted permanently on my old mill/drill. It has a 1" diameter bore and I made an adapter for my 4" scrolling chuck. A threaded backplate and stud keep it securely fastened. To center the table, I put a scrap piece in the chuck and "turn" a cylinder with an end mill. I then use and edge finder to accurately align the true center of of the rotary table with the spindle axis. A test indicator mounted on the spindle would also work well. The mill has a DROView attachment Machining Protocol Examplel.xls and I can set the center better than a thousandth.

I use the table to cut arcs. If the part has a single arc, I position the part so the center of the arc is on the table axis. All the linear features can be made by a combination of x, y and table moves. Just make sure to record the home position before moving and axis! A DRO really shines for this.

Lastly, I had done some very precise pseudo four axis machining by setting the table in a vertical position with the axis parallel with the x axis. The table was centered in the y direction by cutting four square faces, making a cut and rotating 90 degrees and repeating until all four faces were cut. A micrometer was used to measure the resulting square. The end mill position is half the measured thickness. I found the x position by facing the y-z face and locating the edge with a sharp point and a 50x microscope.

A custom tool setter system datum was made from a silver alloy relay contact mounted on the table and wired to an LED indicator. This was because one of the tools used was a .008" micro drill and another was a 0000 center drill. With setup, I could do tool changes very accurately.

Because I was doing some rather complex machining steps, I found it useful to choreograph the machining in an Excel spreadsheet, listing the operation, the face worked , the tool used, the coordinates, and the DRO setting. An example is attached.View attachment Machining Protocol Examplel.xls

 

[Holescreek]

I used the whole shebang last week inletting a block of aluminum for a Mauser stock. The ability to tap holes wherever needed for odd shaped parts really comes in handy. I needed to cut the tapered sides for the receiver tang:

 

[RJSakowski]

Another use for the rotary table is to cut irregular shapes. Any curved surface can be reduced to a series of tangent arc. Kind of like what we did in pre-CAD days with French curves. The trick is to place the center of each arc at the axis of the rotary table. This can be accomplished by mounting an x-y table to the rotary table. It's a kind of kludgy method but it is a way to make cuts that would be impossible without a CNC.

[FONT=&quot]Even highly irregular curves can be machine with relatively few arcs. I once had to accurately cut an Archimedean spiral. It took over 8,000 linear interpolation moves to produce the desired accuracy. The same accuracy was accomplished with 51 circular interpolation moves. It does require some kind of CAD program to do more complicated curves but it is possible to calculate the arc radii and centers and start and end points using Excel.[/FONT]