difficulty mounting X axis scale on Nardini lathe
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  1. #1
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    Default difficulty mounting X axis scale on Nardini lathe

    I am in the middle of installing a Fagor DRO on my Nardini 1440E Mascote lathe. I got the scale bolted onto the cross-slide OK. The long scale along the back of the bed, though, is giving me problems. The bed has casting protrusions that preclude bolting the scale directly to the bed. Hence I will need to make some mounting blocks to space the scale out from the bed to clear the casting protrusions.

    I don't have enough experience mounting DRO scales to know exactly how to design these mounting blocks.
    Some blocks I have seen have set screws to precisely align the tilt of the block prior to mounting the scale. This would be both to have the mounting face both exactly vertical and also exactly parallel to the spindle axis. Then I guess I'd need a hole to screw the block to the bed, and that hole should be elongated so the block can be moved up or down so that both blocks are at exactly the same height. Finally, I'm thinking I will need threaded holes to screw the scale ends to.

    Is there something I'm not considering?

    metalmagpie

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    I do not see why the scale has to be vertical, what am I missing? I suppose it may help to keep stuff out.
    Bill D

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    Quote Originally Posted by Bill D View Post
    I do not see why the scale has to be vertical, what am I missing? I suppose it may help to keep stuff out.
    Bill D
    Well, yes, the reader slot has to be at the bottom so less stuff will fall in. But I'm really talking about the scale being vertical AND THE READERHEAD has to be vertical. If one is cocked w.r.t. the other that's bad.

    metalmagpie

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    I would make a backup spar for the scale to mount to, with countersunk holes for the screws. Then make some spacers with holes for the screw to go through in the middle and a set screw hole on the top and bottom.

    Jon

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    When mounting a sliding scale to a machine, the first thing that I think about is the alignment between the scale and the reader head that slides on it. And any amount of clearance, IF ANY, that those two parts are allowed between them. I try to consider just how much slop there will be in the table or quill movement when they are not locked down.

    In my opinion, an ideal mount for the scale or for the reader head or for both, would allow a small amount of movement in both directions perpendicular to the length of the scale and for a small bit or rotation about the axis parallel to that length, while preventing any movement along that axis. Movement on the scale's axis would equate to errors in the readings.

    There are several ways to create this kind of mount. The simplest may be using flexible strips of sheet metal that would allow at least some of these degrees of freedom while preventing movement on the long axis of the scale.

    All that being said, firm mounts, with no degrees of freedom, can work if there is little slop in the moving part of the machine. This caliper was mounted as a quill scale on my mill with solid mounts. It has been in use for around 10 years and, so far, there are no problems.



    The lower mount, on the quill, has slots for positional adjustment. The reader head is mounted firmly at the bottom of the head casting, but there is an upper clamp on the depth probe of the caliper which provides some of the flexibility that I mentioned above: no axial movement, but it can rotate a bit about the horizontal axis.

    The main thing that I worried about with this mounting was any rotation of the quill about it's vertical axis. One thing that works in my favor on that point is that there is very little freedom for the quill to rotate. As I said, ten + years and no problems. My worst problem with this is battery life.

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    I'll see whether I can get pics from my 1440's DRO attachment without taking things apart later today or tomorrow. It's a Sargon scale, if that matters.

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    Hi
    I have a Nardini that I want to fit with a DRO so following this thread with interest.

    Dazz

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    A single-piece spacer the same depth as the bosses is used on mine, in the center of the scale (or so). The mount is likely bolted to the spacer. The spacer is bolted to tapped holes in the lathe bed casting. The mount might also be mounted to holes threaded in the bosses at either end, but I did not remove the cover to see. Picture (from the top, looking down) attached.



    20191127_163824_080-1-.jpg
    Last edited by n2zon; 11-27-2019 at 04:49 PM. Reason: Add/correct info.

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    I had a similar problem on my Howa. First understand you need the scale mount's needs be "in plane" vertically and horizontally with the reader head that is attached to the carriage.

    I achieved this with 3 mounting blocks, one at each end and one in the middle. The blocks had 4 set screws "at each corner" for pushing the block out from the casting, and two "in the middle vertically" slotted and recessed for socket head screws (drill and tap into the bed) to pull the block onto the set screws and bed casting. These blocks are swept into alignment with an indicator on the carriage bottom, then (and only then) the scale attached and further swept and fine tuned until you meet the scale manf spec for alignment. Took me many hours to get the alignment correct, but my scale is close to 7 feet long and I was working alone. You will need to mock up how you are attaching the head to the carriage first to figure out roughly where the bed scale will attach. Little bit of trail and error. In my case the mount points on the rough casting varied "in plane " by over 1/8 inch from each other. Adjusting the 4 corners into plane is way way better than mucking with shims.

    Size the blocks by estimating the worse case condition along the bed - some may be thicker than others. You will also need two (or more) tapped holes to mount the scale top the block, and you make need to make some custom clamps depending on he scale mount. You might be able to mount with u-clamps over the two ends, but the middle will need clamps/mounting that do not interfere with the reader head travel. Take care you have a means to limit travel of the carriage so the reader head doesn't get trashed on over-run.

    Don't forget to to allow for a simple shield to be mounted above the scale to keep the junk from accumulating in the gap behind the scale and sticking out down onto where the head will ride. Best to have it in a "z" shape over the entire scale protruding as low vertically as you can without head interference.


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