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  • Small CNC mill conversion questions...

    One of my (very) occasional small side projects is helping a buddy re-do a CNC conversion to a little Grizzly desktop mill. The previous owner had converted it with poor screws and kind of sloppy mounts, and I've been trying to fix that.

    It's getting close to finished- at least mechanically- and I've been starting to think about the details. One of he more important ones on my list is oiling the ways.

    As on most of these little desktop mills, there's absolutely no provision for oiling- I presume one is just supposed to blurp oil hither and yon and hope for the best. So I've been toying with the idea of making provisions- like drilled passages, ball oilers, and grooves in the way surfaces. Or just scoring it a touch with a scraper for oil retention.

    And really, I'm wondering if it'd even be worth it. I'd like to do a fairly complete conversion here, and we'd both like this to be machine that will last for a while- if not as much for making actual parts, but also training and practice. While I wasn't planning a pressure luber or anything like that, I figured a couple of channels capped with ball oilers, maybe some felt wipers, and all protected by some accordion way covers.

    On the other hand, just the accordion covers, and the occasional wipe-down and splurt from an oil-gun might do just as well and be a lot easier to boot. The Y-axis ways aren't as much of a worry as the X- oil naturally runs toward the saddle ways, but away from the table ways.

    I've done some minor Googling, and it doesn't seem like anyone who has done a CNC conversion has seemed overly concerned with oiling, so I'm kind of thinking I'm kind of overthinking this.

    Any opinions? Anyone who's done a mini-mill conversion and seen it for themselves?

    Doc.
    Doc's Machine. (Probably not what you expect.)

  • #2
    Just my thoughts as I am in the middle of making a Harbor Freight mini mill into CNC. Caring for the mill is important but for my conversion, production is not on the list, just hobby things. The mill isn't terribly expensive so one compares the cost in time and parts to make the mill better suited for lubricating to what it would cost to simply replace the mill if wear becomes a problem. I suspect my mill will still be as accurate when I give it up as it is now. If not, I will rebuild or replace it.

    If my mill were very expensive and/or I was in a production shop where it would be used all day long every day I might go to more lengths to make it last....or maybe not as I would expect the mill to pay for itself in production several times over and be rebuilt or replaced within a reasonable amount of time.

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    • #3
      I drilled and tapped M6X1 holes, same pattern as gib screw adjusting screws.
      Used M6 zerk grease fittings, and an oil gun, a grease gun converted to use
      way oil, purchased from McMaster.
      Attached Files

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      • #4
        It's not just a matter of reducing wear, but also minimising stick-slip so that the various parameters (accel, IPM etc) are reliable. Not CNC, but I added oil passages/ grooves + GITS cups to my Atlas 618 carriage which allowed me to run the gibs a little tighter but still have the same amount of friction. Also, the easier something is to maintain, the more likely it will be.

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        • #5
          I expect even a desktop CNC could quickly exceed the lubricity of one time applied lubrication. My big mill is a Hurco KMB1 with dovetail ways. It was originally setup to oil with oil metering devices at every lubrication point once every 15 minutes. When I replaced the electro mechanical timer, solenoid valve and pneumatic oiler with an electronic oiler I set it to dispense the same amount of oil every 15 minutes. Oil meter devices ensure that oil is not delivered all to the lowest points leaving others dry. The Tormach spec says to oil every several hours because it has some fancy high tech new way surface material, but I set it to oil every hour anyway. All of my speed masters are set to oil every 15 minutes because I never got a reply from the MFG about how often they should be oiled. I do a lot of small movement cyclical reciprocating machining which could scrub oil off one spot on the ways fairly quickly. A machine that is mostly used for longer non reciprocating movements might not need to be oiled as often. Still it always made me cringe to see small CNC machines that were not setup to be easily lubricated at all. Even most half decent dry machining cnc routers have grease ports.
          *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

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          • #6
            Maybe add some felt wipers to hold some oil?
            Location: Long Island, N.Y.

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            • #7
              Originally posted by RichR View Post
              Maybe add some felt wipers to hold some oil?
              +1 that's all I did to my converted mini-mill and my manual Seig X2. The ways are so small adding ports and grooves just reduces the bearing area. Just some 1/4" thick felt wipers soaked with 10wt oil has worked fine.
              I just need one more tool,just one!

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              • #8
                I have always used Vactra2 waylube oil for ballscrews and ways.
                Max.

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                • #9
                  Wound up adding simple ball oilers. Drilled the gib-side ways in between the adjusters...

                  Click image for larger version  Name:	G8689-163.jpg Views:	0 Size:	48.6 KB ID:	1837790

                  And the left side saddle way in an identical location. The rear one was the only tricky bit- due to my big support frame for the wimpy column, an oiler on the backside would be difficult to access- so I also put it on the left side:

                  Click image for larger version  Name:	G8689-173.jpg Views:	0 Size:	41.4 KB ID:	1837791

                  And milled each way face for a small z-shaped oil channel.

                  Click image for larger version  Name:	G8689-171.jpg Views:	0 Size:	71.3 KB ID:	1837792

                  Might not be the best possible setup, but it's better than what was there (which of course was nothing. )

                  But, with the table reassembled and lightly lubed, that's very close to the last of the major fabrication on this project.

                  Click image for larger version

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ID:	1837793

                  Now I just need to sort out the electricals.

                  Doc.
                  Last edited by Doc Nickel; 11-10-2019, 05:17 AM.
                  Doc's Machine. (Probably not what you expect.)

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                  • #10
                    it is nice having big machines to work on little machines...

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                    • #11
                      Doc, Nice work. Its a good solution with the capability to add automatic oiling in the future if you choose to. In any case, by having oil ports you will more likely lube the machine more often. Atleast every day you use it.

                      Originally posted by skunkworks View Post
                      it is nice having big machines to work on little machines...
                      And little machines to work on big machine too... In the past my little 7x10 lathe has made parts for one of my bigger lathes, and there are parts on my Hurco KMB1 that were made on my Taig. None of my tool racks were made on the machine they are used for. They were setup to be made on the machine that was available.
                      *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

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