# Centering a rotary table under the quill.



## Philipintexas (Aug 15, 2012)

This may be well known to smarter people but I just discovered it out of necessity. 
I often need to center my rotary table chuck under the quill of my Mill-Drill, and I found a quick way to accomplish the task. Center the two visually, then chuck a mechanical edge-finder with half in the drill-chuck (or collet) and the other end in the rotary table chuck. Be sure they are close to centered before tightening the edge-finder. Then slide your fingernail up & down over the mating joint of the edge-finder, while adjusting both X & Y planes, until your fingernail doesn't catch an edge up or down over the mating joint, in either plane. Check it with a mich over the joint and it will be exact or extremely close to centered, depending on the degree of accuracy needed.


----------



## Rivergypsy (Aug 15, 2012)

Holding a piece in both is a tad quick and dirty, but good enough for some work. For precision though, I'd get it all clamped up and then play with the dti


----------



## nemoc (Aug 15, 2012)

For fast centering I put a center in the rotary table and lower the mill head       ( with no tooling in it ) onto it and tighten down the rotary table.  It's close enough for most of my work and very fast.  I have a center with some flats ground on it so it's easy to remove.


----------



## workshopman (Aug 15, 2012)

My method is a variation on nemoc's method and again much quicker than playing around with DTI, etc.
I have plugs that go in my tables bores, a very short Morse plug and a parallel one for another table. Both have been centre drilled to be concentric with their outer diameter. the Morse one is also tapped in the bottom of the centre drilled hole to allow it to be jacked out. 

With a centre in the machine's spindle lower it into the drilled centre and secure the rotary table on the mill table.

If you wish then to centre a chuck on the table the parallel plug can be gripped in it and the centre lowered into it and the chuck then secured to the rotary table.

If you want any more ideas for using a rotary table see here  

Harold


----------



## abby (Aug 15, 2012)

It is not a good idea to assume that the hole in the centre of the table is actually central.
Due to wear or doubtful manufacture only clocking with an accurate DTI will prove how accurate it really is.
The only real way to centralise the table , and it is very quick , is to place a DTI fixed to a magnetic stand on the table in contact with a test bar in a collet , then rotate the table.
This way you can get the table central in a couple of minutes to better than 0.001" which is accurate enough for most.
If you have stops available setting one on each axis means you can move away from centre and back , very handy for some jobs.


----------



## AlasdairM (Aug 25, 2012)

A very similar thread on another forum is http://modeleng.proboards.com/index.cgi?action=display&board=general&thread=6586&page=1

Regards, A


----------



## Brian Rupnow (Aug 25, 2012)

I have a 3 jaw chuck permanently mounted to the faceplate of my rotary table. I have a 2" lenght of 1" diameter brass with a 3/8" hole reamed in it on center. I have a peice of 3/8" cold rolled about 1 1/2" long that I mount in the drill chuck on the quill. I mount the rotary table to the mill bed, then play with the x and y coordinates untill the 3/8" rod will fit perfectly into the reamed hole in the brass without binding when I advance the quill by hand. Its quick, easy, and seems to be accurate enough for any of the work I do.---Brian


----------



## Mosey (Aug 25, 2012)

What about using a centering indicator? There are cheap imports that are fairly accurate, and when you are used to them, can do the job in a minute or 2. Of course, I covet a Blake brand one.
If anyone doesn't know about them, I can post a link, or go to MSC and look up Blake.
I confess, I have the centering indicator but usually use the edge finder in my collet against the Rotary table center hole.


----------



## wild350x (May 24, 2014)

For anyone whom doesn't own it as a professional machinist the book Machine Shop Trade Secrets was probably the best $36 you can spend on learning not only how, but when and why to locate something a certain way as well as techniques not commonly available in online info.


----------



## goldstar31 (May 24, 2014)

The cheap and cheerful way is to put a pointed piece of rod in the centre of the rotary table and another in the drill chuck- and stick a bit of sheet or a safety razor blade I between.
 Adjust it until it doesn't tilt. It works for doing lathe centres and aligning cutting tool height.

 The elegant way is to have two pieces of rod- halved.  With a bit of cigarette paper, you can better 0.002" off cock.

 The latter is not new. George Thomas used it- making his dividing head and Professor Chaddock used it to align the rotary table on his Quorn.  The first one- I think is- Sparey.

 I can get to 0.0002" with a decent dial gauge but with a mill drill- no, not really.

 Regards

 Norman


----------

