If the zero mark is rivetted on it may be worth making a new one with a vernier scale and slotted mounting holes. Then neatly refitting it in the desired alignment using nice neat screws.

On 1 March 2024 at 20:00 Bazyle Said:

If the zero mark is rivetted on it may be worth making a new one with a vernier scale

Why would you want to convert a fiducial mark into a vernier scale?

All it does is keep a gross count of number of whole degrees.

The fine graduations/increments of a rotary table are engraved on the handwheel attached to the worm, not on the table itself.

That is why a bit of tape works as you only need one mark on it.

Andrews method may not work when using the table vertically unless you put packing under it which is not ideal. Also won’t be able to use tailstock support it it is packed to tilt it.

Talking of vertical use at least on my Soba one the mark is not so easy to see when the table is vertical so the bit of tape can be positioned to suit the particular setup.

The position of the slots on a rotary table to the mill axis is academic to the use of the rotary table – they are only there to allow clamping of the workpiece which is relative to ‘Zero’

Once the table is set to align with the spindle set the table dial to zero. Then set the work piece to the mill axis(s) and work from there.

In the image below the slots of the table are not exactly in line to the mill axis but the fixture is being set square to the back of the mill. Some tables have three slots so alignment there is even more irrelevant.

Hope that’s of help – Tug

On 2 March 2024 at 06:55 JasonB Said:

Andrews method may not work when using the table vertically unless you put packing under it which is not ideal. Also won’t be able to use tailstock support it it is packed to tilt it.

When mounting the rotary table vertically I have never needed to align the table slots to any axis. So there is no need for packing. The only important alignment is that the table surface is parallel to the Y-axis.

I don’t have a tailstock for the rotary table. As far as I can remember my rotary table doesn’t have any slots on the underside for keys to align with slots in the milling machine table.

Andrew

The only reason I can see for having the slots in line with an axis is if you have made a specific jig to bolt to it that has the holes in line as trying to make a jig with 5deg offsets would be a PITA.

Having a vice on the table would be one reason if you want to machine a part with angled surfaces such a sthis set up 15 deg either side is easier to keep track of if teh vice jaw and therefore table slots all line up with X axis

On 2 March 2024 at 13:49 Howard Lewis Said:

Why do the T slots need to be aligned with the mill table axis?

It helps on more advanced work when aligning additional features with existing features on the work. Like this:

The slots for the spokes on the top side of the hub have a precise angular relationship with the slots on the bottom side. If the rotary table is set at zero, and one table slot aligned with the Y-axis, then a blank T-nut can be used to locate the work such that machining the slots on the top side, at their given angles, ensures that their relationahip to the slots on the bottom side is accurate. The t-nut can just be seen middle left.

Andrew

I can see Andrews point if you have a double sided part as he shows in his set up but don’t want to make a fixture to hold the part. The table itself then becomes the fixture to align the part but for general usage there really is no need to align the slots – even when using a vise.

Once the spindle axis is set to the RT axis and workpiece axis set on the table relative to the dial reading that’s all that’s required. As said what if the table has only three slot or, as also mentioned , a sub-plate with none – just tapped holes.

If you do carefully align the slots to a table axis any backlash in the (rotary) table – and they all have some – will quickly render the care taken pointless in matching the zero on the dial to the same accuracy. It also means that the slots in the table have to be exactly at 90 degrees to one another to match both axis As they are only there for clamping they will not have been machined with the same tolerance as the mill X and Y axis – they are the controlling factors in X and Y – the RT providing just the angular movement required.