Advice on DRO mounting on Myford VMC

Hi John D

I have a green Myford VMC purchased in 1991. I fitted a 3-axis set of encoders supplied by Machine DRO/Allendale some 10 years ago. I believe these were the glass type as the magnetic encoders were not on the market at that time. It took a long time to fit and I enclose a few photos which I hope you find useful. As previously mentioned, if the X scale is mounted on the front face of the table, then you will lose the end stops and possibly the oil holes. If you fit it on the rear of the table you will lose Y travel.

I have also made a minor modification to the VMC On/Off switch mounting using spare brackets from the DRO mounting kit so the switch faces forwards.

The Sinho DRO display box I purchased has a problem where if you are using any of the special functions such as Pocket Milling, it will not function correctly unless all the measurements are entered in metric. This will hopefully have been addressed by the manufacturers over the years but it did fox me at first! Normal X, Y, Z DRO operation work well. It may be worth checking this before you get going.

Now with apologies for the orientation I include the photos. I have tried rotating these photos both in Windows and the tools in this web site with no luck!

Edited By JasonB on 01/10/2022 15:51:18

Hi Ian,

Thank you for the series of photos. All really clear and the right way up. Its really helpful to see the choices you made - I am now considering going on the front of the table rather thank losing Y axis travel. I think i will end up directly lubricating the table ways so not too worried about obscuring the oiling points. I am not sure how much i would have trusted. used the end stops too. Y axis travel is more valuable i think.

I love what you did with the power switch/ lamp mounting,

One question - was there a reason you ended up with the fairly large degree of stand off on the z axis strip? I was planning on keeping it snog to the pillar withe the stand off dictated only by the slope at the top.

Brian, thank you for the photos. I love the way you mounted the Y axis encoder, really nice. Can i ask what you used for the z axis mountings onto the pillar - i.e. how you kept everything so close/ adjustable? Do you miss Y axis travel or not a problem in reality?

John

Hi John,

Pleased the photos are of some help. Yes, you could possibly mount the Z scale a little nearer the column and save around 1" in its current orientation. It may also be possible to rotate the Z scale vertically clockwise by 90 deg avoiding the large bracket taking the movement to the slide. This would allow you to move the scale even nearer, but at the expense of more complicated fixing brackets. I try to mount the scales with the reading head facing away from the source of the swarf etc.

Not really for this thread, but I have had the Y nut come loose. I noticed this when the DRO Y display showed a different value to what the thimble was showing. When I strip the table to correct this I am hoping to fit a manual pumped oil feed system to all the slides. Lastly, I have also noticed that some R8 tooling has developed a burr on the keyway slot, so something may have damaged the locating pin in the spindle bore.

Regards

Ian

Hi John,

The problem with mounting the Z axis scale on the VMC is that the pillar slopes in towards the top. I got over this by simply drilling and tapping into the pillar and using a screw as a standoff. I can't remember what I did at the bottom, probably a short sloping spacer. I've just taken this photo of it.

As for the Y axis, I did consider the loss of travel when mounting it behind the table, but after nine years there have only been a few occasions where I could have done with some extra room but have always managed to find a way round the problem.

Edited By Brian O'Connor on 02/10/2022 18:16:08

I thought I’d drop a quick update on progress with the DRO install.

The Y axis is done, the knee Z axis is done. I am procrastinating about whether to go front or rear for the x axis. I don’t mind losing the stops but don’t like the vulnerability of having it on the front - but equally I don’t want to lose y axis travel unnecessarily. Also, does anyone know the angle of the dovetail on the front of the table? Or better still where dovetail nuts are available from (I could just by a dovetail cutter I suppose)?

I decided to go with the idea of a combiner and an addition Z axis encoder on the quill. It will only be tiny but a nice addition and not much more money thanks to Tony and Jo at M-DRO.

I’m looking at no-drill mounting options for the quill scale and thinking a machined plate to replace the cap on the left of the head and then a mounting on the top inch or so of the existing scale for the encoder.

Edited By John D on 16/10/2022 18:25:02

Front mount is best for the X. You should already have the captive nuts on the end of the stops which you no longer need. The solution to the Quill is magnetic strip encoder mounted on a plate stood off from the quill scale.
Hope this helps.

regards Martin

Thanks Martin. I’ll go front for x as you suggest. I’ll cut a large chamfer on the back of the L bracket that the encoder mounts on so it clears the oiling points and that way the rail can sit nice and flat just above the two oiling points.

i don’t have any captive bits for the dovetail so hoping I can find a ready source for them. Does anyone know if all the variants of these VMC have the same dovetail size in the front?

It's not really practical to fit the scale on the back of the table. There is no room for it without losing a fair bit of cross-travel; and it would be in the worst place for swarf and coolant. This leaves you little alternative but to lose the stops as it hogs their slot, short of having to build a rigid off-stand for it.

That I found the biggest drawback.

I do not believe this common idea that once you have a DRO you no longer need the stops. If you are making a lot of repeated cuts, such as in milling a large recess, it is far easier to use the display to set the stops then work to them, rather than keep having to look up at the display.

I prefer to augment the machine's features, not just blindly replace them.

In fact I spent a little while yesterday examining my VMC to assess how I can make not only new long-travel stops, but also cross-travel stops it lacked as original design.