# Rotary Table Center Hole ?



## autonoz (Mar 28, 2015)

I just picked up a Made in Japan 12" rotary table. With research it looks to be made by Kamakura. Everything I have read says it should have a 4MT center hole, but this one appears to be threaded. The picture should show you what I am talking about. Im wondering if the previous owner threaded it to put this adapter in it to help lift it or has someone else seen one like this. I tried knocking it out from the back side, but no luck. I imagine it is threaded in. Any ideas to get it out would be appreciated as well.


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## pineyfolks (Mar 28, 2015)

Can you put a bolt in and lock it with a spacer and nut? Maybe it's not that tight just tough to get a hold of. You could mill a slot and make a large screwdriver.......


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## autonoz (Mar 28, 2015)

I tried the bolt and nut already with no luck. I thought about milling a slot, but wasnt sure why it was in there and wa waiting to see if anyone had info on it.


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## kd4gij (Mar 28, 2015)

What does it look like from the outher side. Try putting a plate with a hole in it like a big washer and see if a bolt will pull i out. like A jack screw.


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## autonoz (Mar 28, 2015)

I tried driving it out from the other side. I think its threaded.


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## Navy Chief (Mar 29, 2015)

It certainly appears to be threaded in from the picture. Not sure which direction you tried the bolt and nut trick from, I was thinking that if you can access the threads from the back you could run a bolt in part way, lock it in place with a nut, and continue to exert tightening pressure from the back. This should have the effect of continuing to thread it out the front of the table. I was also wondering if the owner who modified it happened to have applied some red loctite to the threads when it was installed...


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## RJSakowski (Mar 29, 2015)

I would try to verify that the adapter is indeed threaded and if so, whether left or right hand threads.  Can you determine from the backside that there was a 4MT taper originally?  A couple of measurements on the exposed bore should  clarify that.    If red LocTite was used, it is my understanding that the only way to break the bond is with methylene chloride or  heating to something like 250C.  
The big question is what are you going to do when you get the adapter out?  You presumably will have a bunged up Morse taper socket.


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## cathead (Mar 29, 2015)

I'm betting it is a tapered hole.  Can you provide a photo of the back side of this unit?


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## Bill C. (Mar 29, 2015)

That is a new one on me.  Used several but never seen one with a threaded plug.  I wonder if the previous owner had made a special fixture.


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## cathead (Mar 29, 2015)

I'm thinking it is a taper with a threaded end......


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## Tony Wells (Mar 29, 2015)

It does appear to be some sort of insert. If you seriously want it out, and are willing to deal with whatever shape the hole is in, machine it out. You should be able to drill it a good bit of the diameter, then bore it until it is just a thin shell. Peel it out.


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## RJSakowski (Mar 29, 2015)

Maybe bore and ream for 3MT? Depends on how long the adapter is.


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## kd4gij (Mar 29, 2015)

post a picture of the back.


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## kd4gij (Mar 29, 2015)

If infact it is threaded I would drill two 3/16" holes 180 deg apart and make a pin spanner out of a pice of round stock 2 flats on the outher end and 2 dowel pins. heat it with a heat gun and try to unscrew it.

 morse taper is the same taper as taper pipe threads.


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## autonoz (Mar 30, 2015)

Thanks for the replys and I will follow up with the outcome, but out of town for three days. I will work on it as soon as I get back.


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## markknx (Mar 30, 2015)

It appears to be a right hand thread if so I would go with a bolt from the back it the threads in the center go through.  use a couple washers under the head of the bolt. heat may help. but not a lot of it I've seen strange things, but just can't think why you would thread the outside if not to thread it in. Seems an MT taper would pull out if you tightened  anything down on that center thread. Maybe different size pegs for locating parts.
Good Luck
Mark


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## autonoz (Mar 30, 2015)

Well I went to work and was told assignment cancelled. No biggie. A little lost OT, but I get to stay in town. Came home and tapped the plug all the way through and then turned it out from the back. As you can see in the pictures, if it was an MT taper at one point, someone changed it. Now I will have to figure out how to make a centering pin. I was thinking of threading a piece of steel screwing it into the center and then turning it on the mill with the table. Does that make sense?


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## markknx (Mar 30, 2015)

What pictures? Glad you got it out.


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## autonoz (Mar 30, 2015)

Oop! Forgot to attach them.


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## cathead (Mar 30, 2015)

Soooo, do you still have the 4MT inside there?


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## JimDawson (Mar 30, 2015)

Unless that still has a plug in it, it sure doesn't look like a MT4


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## autonoz (Mar 30, 2015)

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.


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## cathead (Mar 30, 2015)

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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## markknx (Mar 30, 2015)

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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## markknx (Mar 30, 2015)

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


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## autonoz (Mar 30, 2015)

The picture looks just like the table I have


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## McRuff (Apr 3, 2015)

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.


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## autonoz (Apr 4, 2015)

I cant picture this


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## McRuff (Apr 4, 2015)

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.


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## gwade (Apr 6, 2015)

Great idea!  Haver never thought of doing it that way.


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## autonoz (Apr 7, 2015)

Going to give it a shot today. Sounds like a great way to center it.


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## markknx (Apr 7, 2015)

Makes sense to me. Will give it a go next time I set up the RT.


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