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Most useful spindle speeds for vertical mill?

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  • Most useful spindle speeds for vertical mill?

    My little Herbert mill has a limited range of speeds and they are a bit of a pain to change too. It's a fairly sturdy little 1950's machine fitted with a 1HP single phase 1450rpm motor. When I got it, the original 3-phase motor had been removed and it had been fitted with a non-original pulley which meant I couldn't swap the drive and driven pulleys around for the full range of speeds on the plate. I remedied that by making a hub for the motor and machining the new pulley to match the original taper but I'm still not happy with it.

    I have a pair of pulleys for a variable speed belt drive coming, in exchange for some work. These allow a range from 1:3 to 3:1, so driven directly from the motor would give a spindle speed range of 480-4350rpm.

    Seems a little high to me at both ends of the scale. I have some other pulleys and belts to adjust it up/down. What would be an ideal range to shoot for?
    Peter - novice home machinist, modern motorcycle enthusiast.

    Denford Viceroy 280 Synchro (11 x 24)
    Herbert 0V adapted to R8 by 'Sir John'.
    Monarch 10EE 1942

  • #2
    It really depends on what you want to mill and with what size cutter. I use the formula RPM= 9000/d (d being the cutter diameter in mm). This is for steel use half the speed for alloy steel + CI, 3 times for Al, from memory, brass is around 2 times. Times the speed by 3 if you are using carbide rather than HSS.
    If you have a quill feed and use the mill as a drill then a top speed as high as 3000rpm might be warranted. If not probably 1500 to 2000 rpm is adequate. Lowest speed perhaps 25 to 50 rpm for a decent sized fly cutter?

    Just my thoughts
    Michael

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    • #3
      Thats good for aluminum and even smaller cutters in stuff like stainless and titanium. I do 95% of my work with 1/2 or smaller end mills.

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      • #4
        Originally posted by form_change
        It really depends on what you want to mill and with what size cutter. I use the formula RPM= 9000/d (d being the cutter diameter in mm). This is for steel use half the speed for alloy steel + CI, 3 times for Al, from memory, brass is around 2 times. Times the speed by 3 if you are using carbide rather than HSS.
        If you have a quill feed and use the mill as a drill then a top speed as high as 3000rpm might be warranted. If not probably 1500 to 2000 rpm is adequate. Lowest speed perhaps 25 to 50 rpm for a decent sized fly cutter?

        Just my thoughts
        Michael
        For carbide you really want a factor of 6-10 rather than 3 compared to HSS. A "safe" starting value for carbide is 120 m/min but generally the carbide bits are meant for 150-300 m/min in steel.
        Amount of experience is in direct proportion to the value of broken equipment.

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        • #5
          My Index 555 is a pretty robust.

          Two speed motor, and v-belts give 12 speeds of: 80, 120, 160, 200, 240, 400, 490, 735, 980, 1220, 1465 and 2450 rpm.

          I tend to run either 490 or 980 rpm, as that is simple via motor speed.

          Tom

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          • #6
            Originally posted by Peter.
            My little Herbert mill has a limited range of speeds and they are a bit of a pain to change too. It's a fairly sturdy little 1950's machine fitted with a 1HP single phase 1450rpm motor. When I got it, the original 3-phase motor had been removed and it had been fitted with a non-original pulley which meant I couldn't swap the drive and driven pulleys around for the full range of speeds on the plate. I remedied that by making a hub for the motor and machining the new pulley to match the original taper but I'm still not happy with it.

            I have a pair of pulleys for a variable speed belt drive coming, in exchange for some work. These allow a range from 1:3 to 3:1, so driven directly from the motor would give a spindle speed range of 480-4350rpm.

            Seems a little high to me at both ends of the scale. I have some other pulleys and belts to adjust it up/down. What would be an ideal range to shoot for?
            put a 3 phase motor and a VFD on it. I had the same problem with my barker lathe, but a VFD solved that. Old iron and VFD is good match, the softstart and stop remove the harshness and the controllabilty of speed is lovely. for me it meant i didnt have to to use the noisey back gear to get from top speed to bottom. The wiring is really easy to do
            Last edited by derekm; 02-13-2011, 02:46 PM.

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            • #7
              duplicated deleted

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              • #8
                Hi,

                The only thing I would be concerned about is boring head speeds. The rest can be worked around. Either by using a carbide tool, insert or solid, or using a small enough diameter tool for the available speeds.

                dalee
                If you think you understand what is going on, you haven't been paying attention.

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                • #9
                  Like derekm, I think your best option is a 3-phase motor and a VFD, with two pulley settings, "high" to give you a speed range with the VFD from about 300 to 1800, and a "low" pulley setting that gives you speeds from about 50 to 300. My experience with a VFD is that below 10 Hz you lose too much torque for it to be practical, so 6X is about the limit for speed change with a VFD. 5X or even 4X would be better limits, if it can be arranged.

                  I find that I run my milling machine around 800 to 1000 rpm for most milling. When using a boring head or large-diameter slitting saw I may go as low as 100 or 200 rpm.
                  ----------
                  Try to make a living, not a killing. -- Utah Phillips
                  Don't believe everything you know. -- Bumper sticker
                  Everybody is ignorant, only on different subjects. -- Will Rogers
                  There are lots of people who mistake their imagination for their memory. - Josh Billings
                  Law of Logical Argument - Anything is possible if you don't know what you are talking about.
                  Don't own anything you have to feed or paint. - Hood River Blackie

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                  • #10
                    Yeah I realize that would be the simple option but I don't have a few hundred quid to spend on it right now - the stuff I have has cost me some time on the mill & lathe and no more.

                    I don't use a large flycutter on it but I do use smaller milling cutters and do a good percentage of ally work. The original range was I think 320 - 2000rpm, I'll see if I can extend that both ways.
                    Peter - novice home machinist, modern motorcycle enthusiast.

                    Denford Viceroy 280 Synchro (11 x 24)
                    Herbert 0V adapted to R8 by 'Sir John'.
                    Monarch 10EE 1942

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