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Uprating a motor on a 12x36 import

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  • Uprating a motor on a 12x36 import

    I'm going to be swapping out the motor on my lathe to 3 phase now its in the new workshop, and while thinking about it i wondered about adding an extra hp.

    Its currently 2hp (supposedly) and i was thinking about putting in a 3hp in. its not that much of an increase but before i do it i was wondering if it would likely damage anything? anyone done it? or any thoughts?

  • #2
    the gearbox in those things is all reasonabley big metal gears so I don't see why it would'nt do another hp easily, however do you really need another hp? Do you really take cuts deep enough that you have stalled out the motor?

    Iv only once heard my 12x36 lathe bog down and I was taking frightening deep cuts and stupidly high SFM with high feed and carbide inserts, like 0.2" DOC in aluminum.

    Of course, the motor will only draw as much power as the torque load you apply to it (plus some other losses but whatever), so a 3hp motor won't draw that much more power then a 2hp motor untill you exceed 2hp, and overall the 3hp motor should stay cooler at the same torque output as the 2hp, But of course, it will cost more.

    Basicly it just comes down to: Do you actualy need a bigger motor more then you need $100 (or whatever the hp diffrence costs) for something else?
    Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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    • #3
      Well...

      I did it on a 9 inch I used to own, never had an issue or problem due to that. I could see however where problems could arise with gear train parts (depending on design and construction) and I'd simply be inclined to say this. IS your machine really...

      A. In need of the HP boost.
      B. Built well enough to handle the extra HP.

      Personally I'm close to replacing the motor on a 12x36 Clausing and I have considered the same thing. I would certainly like the extra HP for roughing but on the occasions that I push the machine that hard I do find myself listening for potential problems. Indicator number one that I shouldn't go to higher HP.

      Secondly I KNOW without a doubt that the machine has failure prone parts and that they have been broken in the past... I can't in good conscience push harder than the machine is capable of pushing now.

      There's probably a good reason that the lathe you run has a 2HP motor on it instead of a 3 now.

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      • #4
        I am currently doing the same thing on my 12x36 lathe. Although the motor plate is stamped as 2 HP, as you pointed out - it is more likely closer to a 1-1/2 in reality. Maybe they confused their lathes with air compressors?

        I simply went with what should be a true 2HP 3ph motor, thinking it will still have more power than the original motor without going overboard. Just my thoughts - I'm certainly no expert.

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        • #5
          I doubt most people ever cut stock on a lathe where they need that much HP. Personally, I don't take that big of cuts. I have however seen a fellow that definitely used every bit of HP available to him, but that was a production set-up.

          Regardless of whether you up the HP or not, get a VFD. They are not expensive and once you use it, you'll never go back.

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          • #6
            yea if anything get a VFD over another HP, though a 3hp motor will let you use your full 2hp when the VFD is set to low freqency (rpms) as motors do derate with speed
            Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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            • #7
              Go for it but while you're installng a three phase motor run it from a VFD.

              It's a machine tool in a home shop. You're not driving a pump or a conveyor where the load is full and contant. You wll hardly ever take capacity cuts. 90% of the time the motor (and gearing) will loaf along at partial load.

              The few time you do load the machine will mean the gearing will be functoning above intended load but so what? There is (or old be) a designed in robusticity put there by the engineers as "safety factor." Your headstock gearing will therefore last only 50 years instead of 60.

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              • #8
                Originally posted by sconisbee
                Its currently 2hp (supposedly) and i was thinking about putting in a 3hp in. its not that much of an increase but before i do it i was wondering if it would likely damage anything?
                The Chinese have little bitty horses. The general rule of thumb is that a Chinese motor is about 1/2 to 2/3rds it's rated power: 1/2 the power for fractional horsepower motors, 2/3rds above 1 HP.

                So if you replace the Chinese 2HP motor with Western or Japanese 2HP motor, you'll have a large increase in power, and it will be smoother, less noisy, and last a lot longer as well.
                "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                • #9
                  I have two 12 x 36's, both upgraded to 3ph.

                  One has a 2 hp motor with an old fashioned VFD. It took a lot of tweaking on the VFD settings just to equal the torque of the original 1ph motor.

                  The other has a 1.5 hp motor with Teco EV vector drive VFD. It has more torque than either the 2hp 3 ph or the original 1 ph.

                  So..... get a vector drive, and don't worry about motor hp. 2hp VFD's cost less than 3hp VFD's so I'd stick with 1.5 or 2 hp motors. If that's not enough power then you probably need a bigger lathe anyway.

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                  • #10
                    Originally posted by rws
                    I doubt most people ever cut stock on a lathe where they need that much HP. Personally, I don't take that big of cuts. I have however seen a fellow that definitely used every bit of HP available to him, but that was a production set-up.

                    Regardless of whether you up the HP or not, get a VFD. They are not expensive and once you use it, you'll never go back.
                    I use every bit and a bit more of the hp available, budget is tight which is why i haven't upgraded the lathe, and as its running around 6 hours a day its doing just fine, i just need more hp at the spindle especially when dealing with larger diameter stainless and cupronickel's. It will eventually get replaced as the workhorse for larger stuff by a dsg or similar if i can lay my hands on one cheaply.

                    A vfd is off the table for now, and as i have 3phase available i may as well gain the benefits rather than just upping to a 3hp single phase.

                    A vfd will come later, just not yet.

                    And i know the chinese horses are smaller, and depending on where i can lay my hands on a motor it might end up being a chinese 3 so that means ill end up in theory with a real 2hp.... in theory, it will fill the gap untill i can build funds but moving the shop has killed my finances for a while.
                    Last edited by sconisbee; 11-28-2009, 01:55 PM.

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