Rotary Table Center Hole ?

Unless that still has a plug in it, it sure doesn't look like a MT4
 
If it is, its not very precise. If you look at the middle picture it appears to be out of round. It's also not very long.
 
I would try reinstalling the threaded part and screwing in a bolt against a heavy piece of plate. Tighten it is much as you dare.
Then give it a blast from the rear with a drift and a large hammer or possibly put it up side down on a press and apply pressure.
Is the material in the hole hardened? If that doesn't work I would get out the drills. I can't tell if the
hole goes all the way through. By the looks of it I would say to drill it out some , then center
the table over the mill and use a boring head.
 
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The smaller dia. bore Looks kind of bluish and grainy. From the picture it almost looks like anchoring epoxy could that be. Like maybe someone tried to epoxy a MT-3 in there also I found some rotary tables with what looks to be a screw in plug like this one.
Mark
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Looking and thinking about this I think the mod was for bolting down parts at the center, or a fixture for production work. maybe circular hole patterns on the drill press. I just say drill press because all the bit marks look like drill bits.
Mark
 
Just an FYI, you do not need a hole in the center of a rotary table to locate it, in fact in my 34 years of machining I have never used that to center the table as most of them are not that accurate and if you use a rotary cross slide there are no center holes. Take a small magnet with asn indicator and position it on the top of the table and rotate the table around the spindle taper the cutter or a dowel pin in the collet. That is the most accurate way to locate the center of the table anyway.
 
First eyeball the center of the mill spindle over the center of the rotary table. Then take a small mag base and place it on the rotary table with the arm extended to the spindle of your mill, place a test indicator in the arm of the mag base and bring it in contact with the spindle.
Now crank the rotary table around the spindle moving your mill table till the reading is even all around, now for more accuracy use the indicator on a cutter shank in the collet. Easy and better than the hole, I have seen the hole on some rotary tables out by more than a thousandth.
 
Great idea! Haver never thought of doing it that way.
 
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