Rotary table centres

My 8" RT has a MT3. I'd go for the largest table that you can handle or fits. The more T slots the better for clamping things to it. The table gets looking a lot smaller by the time you have to clamp the work on. I bought an 8" three jaw chuck that has bolt holes thru the face for mounting. My RT only has 3 T slots but that makes it easy to mount the chuck. By the time the chuck is mounted the entire ass'y is too heavy for me to handle. I turned a bar of steel with a MT3 that I use to center the chuck. Put wrench flats on it so you can get it out! I ended up making an 11" diameter auxiliary table with more T slots and surface area.
 
I have a Vertex 6” RT with a MT#2 center hole.
I use it often with the 2-1/4” 3 & 4 jaws off of my DB200.
I made a #2MT mandrel with 3/8-16 draw bar threads & M12-1 threads to mount the chucks on.
I also have #2MT centering plugs to mount larger chucks.
 
My rotary table uses an mt4 and is too short to hold some mt4 items so I have been turning my own tapers to index stuff. While not ground, the turned ones have been close enough for me. I added a central thread in most so I can use a dowel puller to remove the index pins.

I finished my chuck mount and plan to make what t think @Larry$ describes to center the chuck and be removed so the Mt socket can be used to help swallow longer parts.
 
David your mill/drill is like mine with fixed dials. No zero feature. One nice thing about the fixed dials is that you can dial in the rotary table on one side of the mill table and leave it there. Write down the X & Y coordinates with the direction of table movement. All it takes to center the rotary table under the quill is to move the mill table to the coordinates. One caveat. If you move the head you have to bring the head back to the same place for the coordinates to work.

An 8" rotary table will be quite large on your mill because the overall size is bigger that 8". Something to consider.
 
mickri said:
David your mill/drill is like mine with fixed dials. No zero feature. One nice thing about the fixed dials is that you can dial in the rotary table on one side of the mill table and leave it there. Write down the X & Y coordinates with the direction of table movement. All it takes to center the rotary table under the quill is to move the mill table to the coordinates. One caveat. If you move the head you have to bring the head back to the same place for the coordinates to work.

An 8" rotary table will be quite large on your mill because the overall size is bigger that 8". Something to consider.
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Yes, I did some measuring tonight and an 8” table is too large I think.


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For mills, a large rotary table/indexer has the same challenges in the Z axis as really large vises and other fixtures. My mill has about a 16 inch Z axis workspace, as such, the table would not likely be happy with an 8 inch rotary table.

I realize that I am only repeating the broad strokes of what has been said by others, but as the original poster stated his mill is an MT taper, that points to it being one of the smaller benchtop mills.
 
benmychree said:
Since the center hole is mostly used for centering plugs, I favor a straight hole rather than a taper.
Click to expand...

It seems like rotary tables can come with a variety of different style center holes. I have an 8" Eron, and a 12" Index (prior to Wells-Index). Both have straight holes. To center the table on the mill I use a dowel pin in an appropriate collet, and move the table to get a proper fit in the hole.
 
My 12" Enco RT has a 1" cylindrical section. I machined a 1" stub for my 4" three jaw chuck and use a drawbar system retain the chuck.

My Tormach 6" 4th axis RT has an MT2 taper and a short cylindrical section. The backing plate for the 5" three jaw chuck that came with the RT has a matching stub. The same plate also fits my 5C chuck.

The way I locate the center of the RT is to mount a small piece of scrap material in the chuck and an end mill off axis. Then I use the RT to cut a cylinder. The cylinder will by definition be concentric with the RT axis. I use my edge finder to find the axis coordinates. It's a simple process and doesn't require my removal of the chuck to access the bore of the RT.
 
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