Hi Tony .

The important thing really is to ensure that the piece you want to machine is running true in the chuck as you can use a wiggler / centre finder to find the centre using the X&Yco-ordinates .

I will run through how i set up my table from scratch but some may have a quicker way .

I have turned a mandrel that is round and parrallel with a 2mt taper on one end as this fits my rotary table and the other end has a large centre that is also tapped 8×1.25 mm so i can slide a tube over the end then fit a large washer and screw in a bolt to extract the mandrel from the taper without moving the roary table and the mandrel is long enough to protrude from the chuck by 25mm.

I fit the mandrel to the rotary table and clock it with a DTI to ensure it runs dead true then i carefully fit the chuck over this mandrel , gently tighten the jaws and nip up the clamp bolts for the chuck .

I then re – check the mandrel is running true and if it is all good i fully tighten the clamp bolts.

I fit a dead centre in the mill spindle and roughly locate the rotary table where i want it on the mill .

Then i simply locate the dead centre into the centre in the end of the mandrel and as i do the whole lot of this operation with the worm disengaged i give it a turn to ensure the centre is seated.

I then lock the spindle of the mill (z axis) and fit and tighten the clamps for the rotary table , i also lock the mill table and zero my X&Y readouts/dials.

If youre chuck is already mounted to the rotary table and running true you could mount up a piece of round bar (silver steel or something that has been turned round and parrallel ) in a collet in the spindle and then clamp this in the chuck to locate the rotary table but this will not indicate the runout of your chuck .

IAN

Not quite with it regarding the ball bearing, if its not to forward a ? where do you put the bearing, do you grip it in the chuck so that when you lower the spindle it square up in its bore.

What i do is put a centre into the job or a bit of scrap whilst its chuked in the lathe, then keeping it in the chuck transfer the chcuk over to the RT and with a running centre in the mill spindle locate it in the centred part this pulls everything true and clamp down.

Stew

Stewart :

Bearing ball not ball bearing . This is a fairly standard way of aligning two hollow shafts end on and is accurate to within a few thou if done carefully . Very prone to errors from chamfers and burring over though .

The only truly accurate method on a manual machine is to use a turn round method with a dial gauge .

Regards ,

Michael Williams .

I've never been happy that my chuck is truly centered on the table so plan to give it a go and see what happens

1) Use the ball to centre the rotary table and quill

2) Hold the ball in the chuck and center the chuck to the quill, and hence the chuck to the rotary table.

3) Zero DRO' s for reference point

4) Rotate the table and clock the ball in the chuck to see if it really is centred on the table

5) Clock the quill to the ball to see how well that was aligned

Pete

Edited By Doubletop on 12/08/2012 10:58:35

I don't often use my rotary table, my method of centering it is to put a @ MT center in the table, and a piece of steel bar with a center hole in the chuck of the mill, bring thetwo centers together, and tighten the table to the mill. Then to mount the three jaw chuck center, grip the steel barthats in the mill chuck with the three jaw, and tighten that to the rotary table, seemsto work for most jobs. Ian S C

Make a plug to fit the hole in the rotary table and centre drill one end ensuring that the diameter and centre drilled impression are concentric. Give the plug a head so that it will not fall into through the table. Using a centre in the machine spindle lower it into the centre drilled plug and secure the rotary table and lock the X and Y axis.

Raise the centre, remove the plug, place the chuck on the rotary table and place the plug in the chuck and secure. Lower the machine spindle with centre into the plug and secure the chuck on the table.

You now have the chuck concentric with the rotary table and both with the machine spindle. The assembly can now be moved off centre to perform the task require.

If your table has a Morse taper than you will need two plugs though the taper one needs only to be short and perfection of fit is not necessary.

This is just a variation on Ian C S,s excellent method, especially if your table has a Morse taper.

For more detail on using a rotary table see here

Harold

Hi Michael

I'm having a bit of trouble visualising that – how about a photograph?

How too to produce an " accurate" ball and what size?

N

Hi Michael

I guess thats pretty much like a ball and socket camera tripod head LINK then with an additional ball attached in place of the camera. Interesting but a little too refined for my humble efforts I suspect!

Thanks

Norman

Wondering that nobody mentions the 'Osborne maneuver'. Does not need a DTI, only an edge finder and somethin exactly round and of known diameter, e.g. a ring from a ball bearing. called disk in the description below. For a R.T. you can use the outside; possibly even for a chuck if you don't get in conflict with the jaw slots.

Shameless copy from the Practical Machinist forum:

> Here's the Osborne maneuver:

Measure diameter of disk carefully before starting. Put edge finder in mill.
With disk mounted on mill, line up approximately at center of disk.
Move off the left-hand edge, then move back and find the left edge of the disk with the edge finder.
From that point, move to right a distance equal to disk radius plus edge finder radius.
Move off top of disk.
Move back and pick up top edge of disk with edge finder.
Move down distance of disk radius plus edge finder radius.
Repeat above sequence for X-Y again, and you'll be very close to the center, especially if your starting point was reasonably close to the center to begin with.
You can repeat again to improve even more, but after that you probably won't gain anything. It converges pretty fast. <

Greetings, Hansrudolf