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  • Contrasting metals, or another idea?

    Hi,

    I'm working on a desk clock housing, made out of polished aluminum. Here's a picture of the clock face (this is just an experimental test piece, so there are varying levels of carefulness and polish on it):



    I want it to be somewhat industrial looking, so my original thought was to have the hour marks be simple 1/8" deep holes in the 1/4" thick face (1/4" diam. for 3, 6, 9 and 12, and 1/8" diam. for the rest). That looks a little too industrial, so my next thought was to glue in or press fit a piece of brass in each hole. You can see that in the hole on the left (barely):



    That does not have nearly the contrast I was looking for when polished. I also tried painting the inside of the hole with black enamel (see the middle hole, above), but that seems to emphasize the machining marks (although that did not come through in the pic).

    I thought I might leave the brass inserts somewhat proud (protruding), but the side finish on the inserts is a problem. I am somewhat limited by not having a lathe, but it is possible for me to turn down round stock with my mill and rotary table (which is how I made the press fit brass button), but the finish is not good with my first attempts. You can actually see the irregularity in the photo, where the brass insert doesn't quite reach the side of the aluminum hole. I haven't tried mounting the rotary table on its side and milling down the brass stock with the end of the mill, instead of the side. Perhaps that will work better.

    There is also the possibility of reaming the holes to the exact diameter of the pre-made brass stock. However, looking at the prices of hand reamers at McMaster-Carr, that seems to be a non-starter at the moment.

    So, I'm left with two questions. One, is there a material with a fairly high contrast with polished aluminum, available as rod stock, with characteristics that will allow it to be faced and polished as a single unit with aluminum? Two, any hints on how to reduce the diameter of brass rod with a mill and get a good finish, so I can leave the inserts proud? Unfortunately, buying a lathe is out of the question, at least this year.

    -Pete
    I just like to make stuff.

  • #2
    Thought about home anodization to have colored aluminum buttons pressed in?
    Last edited by Black_Moons; 11-01-2009, 04:24 PM.
    Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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    • #3
      Wood might look nice too. Just a thought
      Feel free to put me on ignore....

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      • #4
        You can turn small stock with a mill.
        The basic difference between a mill and a lathe is:
        Lathe) part spins - tool doesn't
        Mill) tool spins - part doesn't

        sooo...

        Chuck the stock into your mill holder or drill chuck. Clamp a tool bit in the vise. You've just turned your mill into a lathe. Congratulations!
        Start up the spindle and move the table to feed into the stock. The knee will serve as your longitudinal feed. You have to divide by 2 on the mill crank dials for diameter adjustments, i.e. .005" movement will remove .010" more off the diameter.

        Copper might provide more contrast but it seems a little more hard to acquire, though not too hard. How about black delrin? (careful polishing though as it might want to melt if you linger too long).
        Last edited by tyrone shewlaces; 11-01-2009, 04:39 PM.

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        • #5
          Why not drill through holes and ream .0005 under? Non-adjustable reamers are cheap, and you can use stock size brass or copper rod that way. Before pressing in inserts, polish their ends in the drill press or mill against very fine wet dry paper... Finish face w/ pressed in inserts w/ increasing fine wet-dry sanding paper, used wet...

          - Bart
          Bart Smaalders
          http://smaalders.net/barts

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          • #6
            You need more contrast for the 'buttons'- another option is to drill the holes like you did, then carefully drop some epoxy into them. You can have that as a recess, or drip in enough to make them proud of the surface. It will settle to a nice smooth finish. If you drill, then chamfer, you will leave a slight ridge at the top of the hole, and the epoxy can use that to define it's height in the hole. Obviously don't overfill.

            You may find some dark color, or you can mix in some graphite powder to give it color. This looks quite nice, actually. Don't use five minute stuff for a project like this.
            I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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            • #7
              Get some mild steel tubing, or even better bore a piece of bar to fit the brass.
              Then just cut the tube into rings and oil black the tube (heat it to brown/blue and drop it some old engine oil), press fit/glue the brass into the ring and you have a contrast edge that will highlight the brass.
              This is an old trick from hand rendering design sketches, and the black edge 'lifts' the part off the background and gives it a hard edge.

              This is old rendering from about 20 years ago that shows how it works.

              Black Edge


              Peter

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              • #8
                Continue as you are with the brass. When done use a mild solution of Liver of Sulphur and wipe down the face. The brass will turn very black but the aluminum will be unaffected. You can probably pick up a small amount of Liver of Sulphur from a local jeweler that actually does repairs and sizing. Tell him what you are doing and he will explain how much to mix up in water. It stinks a bit but is relatively non toxic.
                Free software for calculating bolt circles and similar: Click Here

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                • #9
                  Originally posted by Evan
                  Continue as you are with the brass. When done use a mild solution of Liver of Sulphur and wipe down the face. ... It stinks a bit but is relatively non toxic.
                  Do not, however, let the solution come in contact w/ acids as the resulting large quantities of hydrogen sulfide are quite toxic.
                  Bart Smaalders
                  http://smaalders.net/barts

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                  • #10
                    Good advice although I can't think of a reason to have a jug of acid handy at the same time...
                    Free software for calculating bolt circles and similar: Click Here

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                    • #11
                      Pete I think go Jesse James and put some .44 mag shells with the primer end up or .45 acp something like that ,,,my .02 worth.

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                      • #12
                        Use grey plastic, or black plastic? Different kinds of wood? Copper?
                        I think it looks pretty nice with the black paint, though.
                        --
                        Aaron

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                        • #13
                          Screw a big ole square-head brass bolt in the hole, head on the face side.

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                          • #14
                            Copper or brass rivits perhaps? Very industrial looking and you can get them with button heads, countersunk etc and you can glue, solder or press them in if you don't wan't to buck 'em. They will polish or accept chemical treatments too.
                            Last edited by chipmaker4130; 11-01-2009, 11:48 PM.

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                            • #15
                              ... although I can't think of a reason to have a jug of acid handy at the same time...
                              I guess drink coffee instead of orange juice that morning.

                              darryl's idea about filling with epoxy might be good. One neat thing I used to do with epoxy is to color it with powdered tempera paints. Add some black and it makes the epoxy cure a nice black color. Using tempera paints, you can mix about any color you'd want. Just a little powder works fine so no need to add too much.

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