Best location for DRO display on a cylindrical grinder?
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  1. #1
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    Default Best location for DRO display on a cylindrical grinder?

    I'm adding a 2-axis DRO to my sixty-year-old Studer RHU-450 cylindrical grinder. Where's the best place to mount the display? I'll make vertical post that comes up from the side of the machine with a movable horizontal "swing arm" at the top holding the display. The question is, should the vertical post come up from the right side of the machine, behind the table and to the right of the tailstock? Or should it come up on the left hand side of the machine, behind the table and to the left of the workhead? When I am using the grinder I tend to stand on the right of the grinding wheel so was inclined to put the DRO on the right side. But perhaps that's a mistake and I should start working on the left and locate the display there. In looking at internet photos it seems like DROs are mostly on the left.

    Here's a photo soon after I got it, showing what the machine looks like


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    Ours is to the right of the headstock behind the table with enough room to change belts comfortably at eye level. Seems comfortable and at the right place to me.

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    Quote Originally Posted by RJT View Post
    Ours is to the right of the headstock behind the table with enough room to change belts comfortably at eye level. Seems comfortable and at the right place to me.
    Thanks for the helpful reply. I've looked at this some more and what you've said makes sense. If I put the DRO behind the tailstock it will crowd the adjustments for the grinding wheel head and its motor/belt drive. So behind the headstock it is, more to the center/left than to the right.

    I had planned to fabricate my own mount, but stumbled across a used one for fifty bucks that is nicely made and a perfect fit (photo below). There's only one fly in the ointment. The place I need to attach the mount (photo below) is the outside of the coolant tank! This is a 45 liter (12 gallon) tank that's integrated into the casting and runs along this entire side and the back as well. So if I drill through the 12mm (1/2") cast iron wall here, I land in the coolant tank. So next question: is it OK for me to do that (with suitable thread sealant and so on)? Or is that a Bad Idea and I should find a different place to mount? Or would it be smart to epoxy a mounting pad onto the outside to avoid drilling through the casting?

    My inclination is to drain the coolant tank, drill through the wall, and attach the mounting bracket there. But before I do that I want to know if the old hands here think that's a lousy idea, or have a better way. Specifically my plan is to cut piece of 12mm (1/2") steel plate to a snug fit inside the DRO mounting bracket, and drill and tap it for four M8 mounting bolts at the corners of that bracket. I'd then attach that piece of steel plate to the outside of the machine, drilling right through the cast iron wall/tank, with a pair of M10 bolts and thread sealant. That would make it possible to remove/replace the DRO mounting bracket without touching the bolts/sealant which hold the steel plate to the outside of the machine. And when I bolt the steel plate to the machine, I can slather the joint with sealant first.


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    Here's how it turned out.

    Because I was drilling through the coolant tank wall, I decided to mount the arm on a 100 x 100mm (4 x 4") sub-plate, made from 12mm (1/2") aluminium. That way the arm can be removed without touching the bolts going through the coolant tank wall, which have thread sealant on them. The sub-plate also adds some stiffness to the arm mount because I milled the perimeter to be a snug fit.

    Here are the four threaded holes. The first one (top right) was a PITA because it came out centered exactly over an internal boss. Murphy strikes again. It took me the best part of an hour to complete the hole with a file then to tap it without breaking off the tap as it started coming through.



    Test fit of the sub-plate



    The sub-plate also provides a good attachment point to clamp the tube for power and signal cables. I don't think it's wise to run these through the coolant tank!



    Here's the roughed-out transition to pass the cables into the machine



    Here's the test fit before painting



    And here's the arm in place. I was afraid that the smaller bolt footprint of the sub-plate would make it wobbly, but it's very stiff, no issues there. You can see how the coolant tank is right behind the mounting point. The little tube leads down to the first place that I could get through underneath the tank.



    I mounted the arm far enough back and high enough up that it's idiot-proof. The arm and display can not be swung into a location that would interfere with the workhead.

    Last step is the cables. I'm going to use Cat5 ethernet cables because they are small enough to thread through all the openings without removing/resoldering connectors, with DB9-RJ45 converters on the ends.

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    Looks like the factory did it, perhaps even better- nice work!

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    Quote Originally Posted by Colt45 View Post
    Looks like the factory did it, perhaps even better- nice work!
    Thanks. I am not shy about modifying/improving my machines but try and do it in a way that's consistent with what the factory would have done. Also got lucky finding a used DRO mounting arm that fits and works well.

    I've been asked how I mounted the scales. Here's the cross slide scale. It's a SINO KA500-70 with 0.5 micron (0.00002") resolution and 70mm (2 3/8") of travel (64mm are needed). This sits on a pair of aluminium blocks that are held to the cross slide with a pair of M6 bolts plus epoxy.



    The head is held with an aluminium bracket



    To attach the mount for the bracket I made a "fake scale and head" to hold the correct alignment



    Here it is with the mounting bracket in place on the fake scale



    I used that to attach the head bracket to the base of the machine, initially with epoxy and then I added a couple of small SHCS from behind



    This arrangement means that I can detach the glass scale read head from the chassis by removing a single M6 SHCS to lift off the cross slide. Then the scale and head come off with the cross slide. I can also remove and replace the scale from the machine without removing the cross slide, but if you drop a screw you have to retrieve it from the hydraulic oil sump. There is no adjustment possible either in the scale mounting or the head mounting, both are constrained in all degrees of freedom, so it can be removed and replaced without having to align it. (In fact there is no way to align it because there is no space and access for measurement and tweaking.)

    I would have preferred to mount the scale closer to the V way rather than the flat way, and with the head on the same part of the chassis where the lead screw bearing sits. But the location would have been so inconvenient for mounting/dismounting that I gave up trying to find a way.

    Those with sharp eyes will notice that I have added automatic oiling of the cross slide. I'll detail that in another thread one of these days.

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    Ours is to the right of the headstock behind the table with enough room to change belts comfortably at eye level. Seems comfortable and at the right place to me.


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