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  • Turning tools

    I am new to machining and would like to know what are the best tools/procedure for a smooth finish on a turned piece on the lathe. I turned the shaft with a carbide indexable cutter and then tried using a HSS with a flat front edge to smooth the machining marks, but it just chattered when taking a fine cut. The material is 1018 with a speed of 130 rpm at a diameter of 1.5-2".

    Is there a better way of doing this? I ended up using emory to smooth the surface, but would like to get it there with a tool bit first and do less sanding.

  • #2
    mbensema:

    Try running the Carbide at higher speeds - this will give a superior finish to HSS in most instances. A sharp bit with a smaller nose radius and finer feed will give you less chatter. Often running HSS faster than normal will give you a better surface finish.

    Forget the flat wide HSS bit - you cannot scrape metal like you do in a wood lathe. You can, but it is going to chatter like crazy and the surface finish will blow chunks!

    The way you were try to use the HSS bit was as a "wiper". A wiper cuts the crests off between the feed path of the bit. You do not have the proper tools to do this. It requires very ridgid equipment, high horsepower, and carbide inserts of a specific geometry. They can cut twice as fast as a normal insert or produce twice the finish at the same speed. You had a great idea, but the wrong tools to be able to do it.

    Try it again - you will figure it out!

    Dave

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    • #3
      Thanks Dave, I will keep trying. I'm making some tools for myself so the finish is not important yet, just want to figure it out before I do need to do it right.

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      • #4
        I'm partial to HSS, but you do need to get the angles correct. As Thrud says though, you can't scrape, you need to cut. A lot depends on what you're cutting, too. Generic "mild steel" doesn't machine to a particularly good finish. Ledloy (12L14) is a lot easier to work with. Drill rod tends to produce a fairly rough finish unless you have a wicked sharp tool. Cutting oil helps.
        ----------
        Try to make a living, not a killing. -- Utah Phillips
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        • #5
          I have to agree about the tools, also....the 1018 stuff your practicing on is crap. Even experienced operators have a tough time with it. 12L14 gives a glass-smooth finish that'll make you feel real good about yourself.

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          • #6
            I keep hearing nothing but bad feedback about C1018 from everyone, so why is it so popular? Most metal suppliers stock tons this stuff so obviously manufacturers like it but why?

            Albert

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            • #7
              1018 is a good base for tooling and such things that take impact twist and such. an example would be punch presses. Not as malleable as 11 series of 12 series. Takes a licking and keeps on ticking. Not like 4140 and such. Surface finish is not the most major consideration for 1018 use. It is used for many parts that do Not have to be beautiful, but functional. I have used it for vise fitting bases, general fixturing with bushings, soft vise jaws, general threads applications. 1018 also has some purity problems in some cases with harder spots and softer spots. There are no additives such as sulpher and lead to aid in the cutting process.

              It can be a poor choice for many items where appearance or surface finish are paramount, but overall strength may not be the main consideration. Things like general use show items and such with no massive or structural loading can be 11 series of 12 series. It (1018) is sometimes classified a tool steel by the applications listed above.

              10 18 can be turned and milled quite well with the right rakes and speeds / feeds, and chip breakers. I have made many a prize part out of 1018. My secret has been speed, constant feed, and a finish cut of .005 depth over the radius of the cutter - for example a .0312 radius I would cut .036 depth - prevention of rubbing at the tip, the bane of machining 1018 and many other materials. feed a bit higher for the finish cut, say .003. Still a bit grainy, but more push in the material and less dwell or repeating in the cut each rotation.

              Big time chip breakers, or the material will many times wind around the tool. Lots of cutting juice on a HSS tool. 1018 can be at times abrasive in nature, so wear can be an issue. Juice counteracts this. I actually prefer the good old black pipe cutting oil for 1018, or that nasty way oil diluting Transultex. Heavy coolant mix say 15 to 1 helps here as well.

              Did much of this last evening as a self test, these were my results, based on past experience as well.......

              11 and 12 series work quite well. I like 1117 best, and sometimes order 11L17 or 12L14 for the class exercises for a better finish (makes the troops more confident for when i throw out the 1018, 4150, 303, 400 series and such).
              CCBW, MAH

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              • #8
                Just a note about 4150, I stated something poorly. 41 series steels are good for tool holders and insert holders, and machined heavy function parts with heat treatment. It also takes a licking and keeps on ticking, but has different applications than 1018.
                CCBW, MAH

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                • #9
                  Thanks Spope14 for your explanation. I've never used the 41 series steel. Does it produce better finish than 1018? Also, I haven't really encountered work hardening with 1018. Is this more of a problem with 41 series or other steels with higher carbon content?

                  A;bert

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                  • #10
                    Thanks everyone for your input. My piece of 1018 is a good example of all of your comments. I used a scrap piece of something in the 11 or 12 series a couple weeks ago and it turned great, unfortuately that is too soft for what I need this time. Surface finish was not important, just wanted to practice. It's nice to know I can blame the material and save my self esteme

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