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How to make a very smooth surface on the mill?

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  • How to make a very smooth surface on the mill?

    I need an even smoother surface than a face mill can provide. My face mill can make a mostly shiny surface, but still leaves tiny grooves that you can't feel, but can see. I also noticed a larger groove spacing approx .1" apart, maybe from me turning the hand wheels on the stage in a not perfectly even manner. In the end, I want to wet sand and polish the surface to be mirror shiny. Is there some kind of a buffing or burnishing attachment for the mill?
    Last edited by beanbag; 06-13-2010, 06:45 PM.

  • #2
    Get a piece of plate glass or a cheap surface plate, put the fine emery paper (250 to 400 grit) on it and rub, change to finer grades as you go. You can get up 4000 grit or better at auto supply houses. Be careful to rotate the work so that it is polished flat and evenly all over.

    That's one way, maybe not the best but it works.
    The shortest distance between two points is a circle of infinite diameter.

    Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

    Southwestern Ontario. Canada

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    • #3
      I'm not aware of any polishing technique on the mill. Many guys use a linisher (fancy name for a belt sander with something like 80 or 120 grit paper. From there you can hand sand and it's a simple matter to buff it up on a wheel.

      Mine looks a bit like this only without the 9" diameter wheel on the side. Bought it at a yard sale for $20.00.

      Last edited by Your Old Dog; 06-13-2010, 07:50 PM.
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      • #4
        It sounds to me like you have one insert (or tooth?) in your face mill that's below the others. Have you checked that? What kind of face mill are you using?

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        • #5
          The best finish is usually made with a fly cutter, with a light finishing pass.

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          • #6
            big sharp slab mill in a horizontal.....best finish you can get next to ground
            .

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            • #7
              Try inserts with a larger tip radius,or leave a finish allowance of say .005" and switch to a fly cutter with a fairly large radius on the cutting edge.That edge can be ground back on an angle to the spindle axis and canted to the topside of the toolbit.Kinda of like a sandwedge for metal cutting Hone that edge with a fine hone and use coolant or something like WD to combat chip welding.

              Power feed if you don't have it will help also.
              I just need one more tool,just one!

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              • #8
                Try tramming your mill head with a tenths indicator and see if it doesn't improve the finish.

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                • #9
                  If you're getting visible finish lines that can't be fealt when you drag your fingernail accross them, you're doing pretty good.

                  One trick I used to use on a job that called for an 8 finish on one particular machined face was a cratex wheel. I had to change the tool offset between almost every other part, but I never failed a part for finish specs.

                  The down side is that I had to bring the spindle pretty far up to get the wheel to polish - higher than I could go on a b'port anyways.

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                  • #10
                    Originally posted by PixMan
                    It sounds to me like you have one insert (or tooth?) in your face mill that's below the others. Have you checked that? What kind of face mill are you using?
                    This is very common - inserts are in various grades - but most are only within a couple of thou, and that make a huge difference on a face mill with multiple inserts.

                    As a test - for a finish pass - remove all the inserts except one.. and adjust the doc/feed rate accordingly. of course... the face mill now behaves like a fly cutter.

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                    • #11
                      Tramming, yes. Even the smoothest and best cutting tooling will be leaving ridges if the tram is out. Then there's swarf removal- if it gets dragged under a cutting edge it can leave a groove deeper than what you could easily polish out.

                      Also, how are the table movements- if it's somewhat loose you could be rocking the table a tad when you crank the handwheel. That would give you an 'inconsistency' every 100 thou.
                      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                      • #12
                        Your face mill is out. This is the finish from the facemill I made a while ago.



                        Free software for calculating bolt circles and similar: Click Here

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                        • #13
                          Surface grinder.

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                          • #14
                            Originally posted by lakeside53
                            This is very common - inserts are in various grades - but most are only within a couple of thou, and that make a huge difference on a face mill with multiple inserts.

                            As a test - for a finish pass - remove all the inserts except one.. and adjust the doc/feed rate accordingly. of course... the face mill now behaves like a fly cutter.
                            Presumably adjusting the feed rate to what you would use for a single insert, but leaving all the inserts in place, should give the same result.

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                            • #15
                              Flat out

                              Originally posted by beanbag
                              I need an even smoother surface than a face mill can provide. My face mill can make a mostly shiny surface, but still leaves tiny grooves that you can't feel, but can see. I also noticed a larger groove spacing approx .1" apart, maybe from me turning the hand wheels on the stage in a not perfectly even manner. In the end, I want to wet sand and polish the surface to be mirror shiny. Is there some kind of a buffing or burnishing attachment for the mill?
                              BB.

                              I notice that you didn't say what material/s you plan to cut.

                              Have a single HSS fly-cutter mounted with a very large "curve" shaped (almost flat) cutting edge.

                              Run it over the previous cut - slow revs and "backward" - it will act as a burnishing tool - but keep the job very clean of swarf from previous cuts etc. You will need a good amount of cutting (or tapping) oil and a fairly high feed rate - just below where the "swirls" start to show.

                              Go easy on the "depth of cut" as we want a rubbing action - not a cutting one

                              The edge on a HSS cutter will stand it where-as a TC may not.

                              The end of the "cutter" can also be a small part of a very large sphere - might be even better.

                              In all cases the cutting edge must be very finely honed - and kept that way.

                              Give it a try anyway.

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