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making very small components from A2 or O1

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  • Evan
    replied
    You won't find a machinability index for all alloys. The index can't be used even across all steels with any meaning. Superalloys such as hastelloy don't have much in common with other alloys so there isn't much to compare with that has any meaning.

    Here is the mechanical properties entry on Matweb for O6 tool steel. Note the the yellow highlighted line:

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  • Swarf&Sparks
    replied
    Pardon my ignorance.
    First I've heard of this "machinability" quotient.

    Where do alloy steels (incolloy, hastelloy, 316 SS etc) fall in this scale?

    How about Ti, Cu?

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  • JCHannum
    replied
    From information in several steel and alloy catalogs, it appears that machinability for steel is based on 1212 or 1112 as 100%, while tool steels are based on 1% carbon steel as 100%, which is about 60% machinable compared to 1212.

    Brass is based on 360 free machining brass rod as 100% and aluminum on 2011-T3 as 100%.

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  • Evan
    replied
    Could well be. I haven't looked up any of this and am operating strictly from memory. Whichever it is I don't think there is any particular "scientific" reason for the choice. In my opinion, I would pick the most machinable and set that as 100% with all the others grades being equal or lower. It's a bit of an oxymoron to have a machinability that is greater than 100%. What does it do, machine itself?

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  • Mcruff
    replied
    If I remember right W-1 tool steel is the baseline for machining in my Carpenter tool steel book. All other steels are graded for comparison from it.
    Last edited by Mcruff; 05-31-2008, 12:37 AM.

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  • wierdscience
    replied
    Originally posted by juergenwt
    Use O-1. A-2 is a good steel but you have to heat it to 1750 deg F. and draw at 450 to about 60RC. It does not go to 67 RC.
    Hardness as hardened is 65-67 before drawing,WORKING HARDNESS is 62 on down depending on draw temp.But that's according to which mfg you ask.One says draw at 400f to 62 and another says draw at 300f to 62.Which one is right,probably both

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  • Evan
    replied
    Using the O6 at 120% compared to O1 example, is the O1 the material at 0% (baseline)?
    No, the O1 is 100% machinability. Harder to machine is less than that and easier is greater. It seems to be that they use the most common/popular material as the reference material. I also think that the scale is pretty subjective and depends a lot on your equipment and experience.

    For instance, I don't hesitate to do hard machining of something like a bearing seat, even with an interrupted cut. It isn't going to hurt the spindle bearings on the SB9 since they are plane journal bearings and if it trashes the tool I just regrind it since I use a solid carbide stick and have a handy 10" diamond wheel.

    (BTW, bicycle hub bearing seats are hard)

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  • Philip Bayer
    replied
    I make components for pocket watches, which are obviously quite small. I use O-1 drill rod, and have fairly good success with it. It machines nicely and is fairly easy to polish, harden and temper.

    I am a novice hobbyist, so I would defer to the pros, but I especially like the O-1 rod since it is available in metric diameters and the set of collets to my watchmakers lathe are metric, so it makes things a bit easier in that respect.

    Philip

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  • bhjones
    replied
    Using the O6 at 120% compared to O1 example, is the O1 the material at 0% (baseline)?

    Originally posted by Evan
    Machinability ratings are only useful for comparing like to like, as in tool steel to tool steel. I don't actually know what criteria are used to derive the ratings and they must differ depending on the class of material. Aluminum alloys have very different properties than steel alloys and so machinability ratings in the aluminum alloy ranges will be based on different criteria than for tool steel.

    The rating is referred to what is considered the "standard" of machinability within the group. Again, I don't know who makes that choice. Machinability ratings cannot be compared between different metals. The ratings for bronze cannot be compared to the ratings for aluminum or steel. They are only an indicator within a particular group of similar materials. I do find them to be fairly accurate for most materials.

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  • Evan
    replied
    I bought a 1/2" x three foot stick of O6 some time ago. I ordered it from our local supplier and they had no trouble obtaining some.

    The reason it's so nice to machine is that it has free graphite at the crystal boundaries. It acts as a lubricant much like lead does in free machining steel but of course doesn't have the negative implications.

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  • Guest's Avatar
    Guest replied
    Evan - you are absolutely right about O-6 being easy to machine and to harden. One question: gmm2 is making small parts - can you get O-6 in drill rod size?
    We us O-6 for draw dies and wear plates. It has that "slick" feeling. Also good for plug gages etc. . O-1 is readily available and cheap in all sizes and keeps a sharp edge when hardened and drawn to light brown (approx. 59-61 Rc.) For gen. purpose tooling I prefer O-1.

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  • Evan
    replied
    Machinability ratings are only useful for comparing like to like, as in tool steel to tool steel. I don't actually know what criteria are used to derive the ratings and they must differ depending on the class of material. Aluminum alloys have very different properties than steel alloys and so machinability ratings in the aluminum alloy ranges will be based on different criteria than for tool steel.

    The rating is referred to what is considered the "standard" of machinability within the group. Again, I don't know who makes that choice. Machinability ratings cannot be compared between different metals. The ratings for bronze cannot be compared to the ratings for aluminum or steel. They are only an indicator within a particular group of similar materials. I do find them to be fairly accurate for most materials.

    Leave a comment:


  • bhjones
    replied
    Evan, could you elaborate on what the machinability ratings mean. I've noticed this rating in various places and I'm like to better understand it.

    Thanks.

    Originally posted by Evan
    The most easily machined and one of the toughest of the tool steels is O6 tool steel. It has a machinability rating of 120% compared to O1. It is ideal for making small parts and gives a beautiful finish with ordinary HSS tooling.

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  • Evan
    replied
    A basic rule of thumb re hardening steel:

    Straight carbon steels may be hardened by water quenching if they contain sufficient carbon. The amount of carbon is indicated by the last two numbers in the type designation. 1018 steel contains 0.18 percent carbon which isn't enough to produce significant hardening. Any carbon steel that contains more than about .20 % will harden to a degree that depends on the amount of carbon. 1040 steel contains .4% carbon and hardens well. 1090 steel hardens to the extreme and is used for spring steel.

    Alloy steels are usually designated by the first two numbers being something other than 10. They are usually air or oil hardening as a water quench is too abrupt and will produce cracking and/or serious distortion.

    The most easily machined and one of the toughest of the tool steels is O6 tool steel. It has a machinability rating of 120% compared to O1. It is ideal for making small parts and gives a beautiful finish with ordinary HSS tooling.
    Last edited by Evan; 05-29-2008, 04:02 PM.

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  • gmm22
    replied
    Thanks for the interesting and very beneficial replies.

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