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Re: Will I break my HSS EM?

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  • timgoldstein
    My experience is you can safely slot up to 1 diameter deep in aluminum if you have enough spindle HP, coolant to cool the bit and metal as well as clear the
    Message 1 of 14 , Jan 1, 2011
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      My experience is you can safely slot up to 1 diameter deep in aluminum if you have enough spindle HP, coolant to cool the bit and metal as well as clear the chips, and use a good 3 flute high performance cutter. Plus of course your setup has to be rigid enough to handle it. We do this regularly with the Haas. With an YST Alumipower 1/4" 3 flute carbide bit we clear the center of Sherline t-slots with .225" depth of cut and 10,000 rpm on the spindle we cut at 22.5 ipm and have never broken a cutter. While this is not likely to be successful on a Sherline do to the lack of spindle HP and probably some rigidity issues at those high forces, it does illustrate what modern tooling is easily capable of.

      To profile deep cuts like in the video you will want to start with the biggest cutter you can use in diameter and the shortest length possible. The idea is to reduce tool flex as much as possible. Carbide is a great way to get the tool stiffer with all else being equal. Also, use quality tooling, not junk cutters that just don't perform and the bad cut angles and sharpness increase force and then cause deflection and chatter issues. Also use as many flutes as you can on the cutter for profiling. Chip clearance is not an issue and more flutes = stiffer cutter. Plus with limited RPM on the spindle more flutes = faster feed rarates at the same chip load per tooth. I like 3 flutes as a great all around cutter. For profiling 4 is better. But if you need to slot, pocket and profile with the same tool, 3 flute is a great way to go.

      For profiling, I don't like to go more than 3 diameters deep even on a light finish cut. Too many issues with cutter flex and chatter. On aluminum with a decent setup, I like about a .010" finish pass and always climb mill it. With a conventional pass and these tiny step overs, the cutter wants to skate on the metal and not bite in. Causes all types of problems. Rubbing instead of cutting is bad all the way around. Bad surface finish, bad cutter life, bad day.

      Hope this helps give you an idea what is possible. Of course you have to find out what works for your combination of machine, setup, and cutters. The only way to do that is experiment and accept that the cost of learning is some broken cutters and scrapped parts. Hate to think what that cost has been to me. But hey, is ultimately the only way to know for sure. Don't remember who, but there was someone that posted regularly on one of the forums I used to frequent something to this effect: One experiment will beat 100 opinions.

      Tim Goldstein
      A2Z Corp
      A2Z CNC division
      3955 S Mariposa St
      Englewood CO 80110
      720 833-9300
      Toll Free 877 754-7465

      www.A2ZCorp.us/store
      USA made accessories for desktop mills & lathes.
      Specialized tools for the jewelry industry.


      --- In SherlineCNC@yahoogroups.com, "alfredo.corado" <tallerescs@...> wrote:
      > Take a look at this video
      >
      > http://www.youtube.com/watch?v=itqz-7T-24o&feature=related
      >
      > At the end this guy is cutting the whole thick...
      >
      > That's what I want to do, What will be the settings???
    • wongsterwish
      Hi Tim, I was slotting with the sherline s 1/2 2 flute HSS EM to make the antibacklash nut mount for your antibacklash nut to mount the 5mm pitch leadscrew on
      Message 2 of 14 , Jan 1, 2011
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        Hi Tim,

        I was slotting with the sherline's 1/2" 2 flute HSS EM to make the antibacklash nut mount for your antibacklash nut to mount the 5mm pitch leadscrew on z-axis. At .25mm per pass (almost 0.001") and 60mm/min feed (around 2.4ipm), I didn't have much problem with the cut. But when I tried .5mm per pass, the cut became very loud and vibration increased.

        So far I've my x and y converted to the 5mm pitch screw. Almost zero backlash. Love them. Can't wait to get the z done.

        I'll be working on the motor mount to offset the stepper motor as the one you gave me didn't have enough offset for the mod. I'll be using aluminum plate instead of round stock like in Graham's pics as I couldn't be able to find round stock of that size in my bin.

        Could you recommend a step over amount, feed, and speed for me to try for this profile cut? I know I need to experiment a bit to get the best result for my setup but some starting numbers will be good. I've only HSS EM to play with. Some of them are Tin coated (per their box).

        Wishing you and those at home a blessed New Year.

        Regards,
        Wong




        --- In SherlineCNC@yahoogroups.com, "timgoldstein" <timg@...> wrote:
        >
        > My experience is you can safely slot up to 1 diameter deep in aluminum if you have enough spindle HP, coolant to cool the bit and metal as well as clear the chips, and use a good 3 flute high performance cutter. Plus of course your setup has to be rigid enough to handle it. We do this regularly with the Haas. With an YST Alumipower 1/4" 3 flute carbide bit we clear the center of Sherline t-slots with .225" depth of cut and 10,000 rpm on the spindle we cut at 22.5 ipm and have never broken a cutter. While this is not likely to be successful on a Sherline do to the lack of spindle HP and probably some rigidity issues at those high forces, it does illustrate what modern tooling is easily capable of.
        >
        > To profile deep cuts like in the video you will want to start with the biggest cutter you can use in diameter and the shortest length possible. The idea is to reduce tool flex as much as possible. Carbide is a great way to get the tool stiffer with all else being equal. Also, use quality tooling, not junk cutters that just don't perform and the bad cut angles and sharpness increase force and then cause deflection and chatter issues. Also use as many flutes as you can on the cutter for profiling. Chip clearance is not an issue and more flutes = stiffer cutter. Plus with limited RPM on the spindle more flutes = faster feed rarates at the same chip load per tooth. I like 3 flutes as a great all around cutter. For profiling 4 is better. But if you need to slot, pocket and profile with the same tool, 3 flute is a great way to go.
        >
        > For profiling, I don't like to go more than 3 diameters deep even on a light finish cut. Too many issues with cutter flex and chatter. On aluminum with a decent setup, I like about a .010" finish pass and always climb mill it. With a conventional pass and these tiny step overs, the cutter wants to skate on the metal and not bite in. Causes all types of problems. Rubbing instead of cutting is bad all the way around. Bad surface finish, bad cutter life, bad day.
        >
        > Hope this helps give you an idea what is possible. Of course you have to find out what works for your combination of machine, setup, and cutters. The only way to do that is experiment and accept that the cost of learning is some broken cutters and scrapped parts. Hate to think what that cost has been to me. But hey, is ultimately the only way to know for sure. Don't remember who, but there was someone that posted regularly on one of the forums I used to frequent something to this effect: One experiment will beat 100 opinions.
        >
        > Tim Goldstein
        > A2Z Corp
        > A2Z CNC division
        > 3955 S Mariposa St
        > Englewood CO 80110
        > 720 833-9300
        > Toll Free 877 754-7465
        >
        > www.A2ZCorp.us/store
        > USA made accessories for desktop mills & lathes.
        > Specialized tools for the jewelry industry.
        >
        >
        > --- In SherlineCNC@yahoogroups.com, "alfredo.corado" <tallerescs@> wrote:
        > > Take a look at this video
        > >
        > > http://www.youtube.com/watch?v=itqz-7T-24o&feature=related
        > >
        > > At the end this guy is cutting the whole thick...
        > >
        > > That's what I want to do, What will be the settings???
        >
      • alfredo.corado
        Tim loved your comments they are very useful and revealing. As you say, I will experiment with different variables. Thank you very much for your efforts and
        Message 3 of 14 , Jan 3, 2011
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          Tim loved your comments they are very useful and revealing.

          As you say, I will experiment with different variables.

          Thank you very much for your efforts and kindness in sharing your expert knowledge.
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