Aligning a Rotary Table

Aligning a part on the rotary table can be tricky and this is just a simple rough and ready approach to aligning a part.

What I’m actually trying to achieve here is the alignment of a workpiece on the rotary table and the first task is to align the table centre with the spindle.

The first thing I did was to put a 2MT fixed centre in the HV4 rotary table.

A centre in the main spindle and a careful view from all angles to check that point meets point.

I viewed this from all angles to check the alignment before I locked the XY travels.

I then placed the workpiece on the rotary table and with the centre in the spindle I aligned the workpiece and clamped it to the rotary table.

This is not a perfect alignment, but it does work rather well.

I used this method to put holes in the cam gear for my transitional engine and the results are rather good.

Another case of me using the long T-nuts to effectively extend the working diameter of the rotary table. This has raised the question of the most accurate alignment of the milling machine and so I’ve tried a few methods.

Alignment by Eye

This was just a simple case of trying to eyeball the two shafts from different angles and aligning them.

I then checked the alignment using a dial gauge fitted to the mill spindle that I could rotate around the spindle and get the maximum displacement.

Using this method I was out by 1.666mm – this is a large error, but I didn’t really help myself as the spindles are a long way apart.

When looking at this in detail I actually got the main x-axis better, but messed up the y-axis as I didn’t spend enough time looking at it from the side.

Centre to Centre Alignment

As there are two points this should be much better – a big error can occur if the points are blunt or even worse damage due to being dropped.

The error was also dependent on how good the 2MT taper is aligned, but this is also true in that I’m using another 2MT part as the reference and it is being taken in and out regularly.

The accuracy on centre to centre was 0.104mm

I reckon I could get this even better with some time allowed to ensure the points were sharp and rotating the point in the spindle to again remove any runout.

Laser Alignment on Edge

Using my laser aligning tool that I made some time ago inspired by Dan Gelbart. This one can be tricky as it so depends on the quality of the circular edge/mark.

You can see the flash of the light on the edge and some movements on the X and Y axis allow you to see the response of the light and to ensure it is the same all the way around.

Using this method as tested with the dial indicator I got to 0.190mm

Laser Alignment on Centre

Someone suggested to me that I would be better aligning on a centre as you can move the X and Y axis and you can see the shape change.

If you look at the centre from the side, as in the photo, it appears as a horizontal line when you’re on centre.

Again I checked using a dial indicator and got 0.242mm and so this really wasn’t the best method – this is only for me and maybe I’m missing something.

Looking at it now I might have been better to align on the silver to black transition from cone to cylindrical shape of the centre.

Laser Alignment on Raised Cylinder

Trying to make the alignment on a circle easier with the laser.

The only trouble here is that the edge of the cylinder has a chamfer and I must admit that a hard sharp edge is better.

I did though get to an accuracy of 0.160mm

Dial Indicator

This was the last method I tried and with ease I got to an accuracy of 0.020mm and with another 5 mins I would have got this down to 0.005mm

All of these methods have there pro’s and con’s. The dial indicator is the most accurate, but this is not always easy to set up and sometimes impossible for certain configurations.

 

About Nigel 192 Articles
Have been making models since I was around 7 years old and using a lathe from the age of 11, a self taught engineer with a passion for making model engines.

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