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  • Motor with clutch for home shop machines?

    When I watch videos of the big iron lathes and even the similar size lathes to what I have but which are more seriously intended for commercial shop use I see that the common setup is a motor that starts and runs constantly for the whole time and that the lathe is clutched in and out and often has a brake built into the action of the clutching handle. (Edited- WOW! that was a long sentence!)

    I'm just wondering if anyone has modified their "home" lathe to add such a clutch and perhaps the brake as well.

    Seems like it would make things a lot easier on the poor motor.

    Or does the use of a 3ph motor and VFD effectively replace such a clutch and brake setup?
    Chilliwack BC, Canada

  • #2
    My small (7x12) home lathe uses a DC motor and so it comes to a stop when turned off.

    The bigger one (9x20) has a belt drive with a handle to take the tension off to stop it. The motor does spin all the time. When I get a round Tuit I will replace the motor with the Consew brushless DC motor that I bought two years ago. Then the belt will only need to be moved to change gear ranges.

    Dan
    At the end of the project, there is a profound difference between spare parts and left over parts.

    Location: SF East Bay.

    Comment


    • #3
      Originally posted by BCRider View Post

      Or does the use of a 3ph motor and VFD effectively replace such a clutch and brake setup?
      Yes. This is a new and better way. The soft start and electronic braking of a VFD is just better. I modified a colechester lathe by removing the brake and clutch and never looked back.
      "...do you not think you have enough machines?"

      Comment


      • #4
        VFD is better solution in almost every case today. Clutch packs wear, need adjustment etc. Pretty often the solution for aging belt variator or worn clutch pack is to install VFD.

        I have clutch on my small 11x24 Kerry lathe.. Never used it for "real", only time I'm touching it when it starts to slip. Have to engage/disengage it couple of times to make it work properly again.
        Location: Helsinki, Finland, Europe

        Comment


        • #5
          The smoother start also minimizes undesireable motion in the carriage, crossfeed, etc.

          Comment


          • #6
            Originally posted by Glug View Post
            The smoother start also minimizes undesireable motion in the carriage, crossfeed, etc.
            Hear hear, I have to lock the crossfeed on my small lathe if I really want to hit anything within 0,02mm. Otherwise its jumping around randomly when I start the lathe
            Location: Helsinki, Finland, Europe

            Comment


            • #7
              On a big lathe (or any lathe, really), one should spin the chuck one revolution
              to just check if anything is going to hit or make contact with part of the lathe.
              Not so much a problem with shafts, but odd shapes like castings is where this
              step becomes most important. Also good to start an odd shaped piece gradually
              to check for imbalance.
              With a friction clutch, the user had direct control of the speed and torque that
              gets applied to the chuck. With a VFD, you hit the button, and you are committed
              to the motion that it is programmed to give you, unless you hit the stop button.
              With a clutch, the control is all right there, instantly. Any sense of something
              going wrong, the user can back off the clutch lever in an instant. Much quicker than
              hitting a stop button. This is why a clutch is always better for a manual lathe.
              The variety of work is so large, and no one wants to roll a 200 pound chuck and
              probably much heavier workpiece over by hand to check for interference.
              A VFD just can't do that.

              -Doozer
              DZER

              Comment


              • #8
                Originally posted by Doozer View Post
                On a big lathe (or any lathe, really), one should spin the chuck one revolution
                to just check if anything is going to hit or make contact with part of the lathe.
                Not so much a problem with shafts, but odd shapes like castings is where this
                step becomes most important. Also good to start an odd shaped piece gradually
                to check for imbalance.
                With a friction clutch, the user had direct control of the speed and torque that
                gets applied to the chuck. With a VFD, you hit the button, and you are committed
                to the motion that it is programmed to give you, unless you hit the stop button.
                With a clutch, the control is all right there, instantly. Any sense of something
                going wrong, the user can back off the clutch lever in an instant. Much quicker than
                hitting a stop button. This is why a clutch is always better for a manual lathe.
                The variety of work is so large, and no one wants to roll a 200 pound chuck and
                probably much heavier workpiece over by hand to check for interference.
                A VFD just can't do that.

                -Doozer
                You can do pretty much that also with VFD if you just want, takes just bit more effort in setup. You could also add torque control to the "virtual clutch lever" if you want but that is not going to work with the cheapest 80$ chinese VFDs. Tap and crawl at 1rpm with full torque or crawl at 5% limited torque if you wish..
                Location: Helsinki, Finland, Europe

                Comment


                • #9
                  Originally posted by Doozer View Post
                  On a big lathe (or any lathe, really), one should spin the chuck one revolution
                  to just check if anything is going to hit or make contact with part of the lathe.
                  Not so much a problem with shafts, but odd shapes like castings is where this
                  step becomes most important. Also good to start an odd shaped piece gradually
                  to check for imbalance.
                  With a friction clutch, the user had direct control of the speed and torque that
                  gets applied to the chuck. With a VFD, you hit the button, and you are committed
                  to the motion that it is programmed to give you, unless you hit the stop button.
                  With a clutch, the control is all right there, instantly. Any sense of something
                  going wrong, the user can back off the clutch lever in an instant. Much quicker than
                  hitting a stop button. This is why a clutch is always better for a manual lathe.
                  The variety of work is so large, and no one wants to roll a 200 pound chuck and
                  probably much heavier workpiece over by hand to check for interference.
                  A VFD just can't do that.

                  -Doozer
                  Better quality VFD's have multiple "program" capabilities.
                  The Toshiba unit on my big lathe is set up for jogging. I just push the momentary "jog" button (MAZAK labeled it "Inching")
                  5 rpm that stops with braking as soon as I release the button. Faster than a lever!

                  So yes, a VFD "can do that". And like lathes that come with differing spindle drive designs, VFD's come with differing features.

                  Comment


                  • #10
                    Originally posted by danlb View Post
                    My small (7x12) home lathe uses a DC motor and so it comes to a stop when turned off.

                    The bigger one (9x20) has a belt drive with a handle to take the tension off to stop it. The motor does spin all the time. When I get a round Tuit I will replace the motor with the Consew brushless DC motor that I bought two years ago. Then the belt will only need to be moved to change gear ranges.

                    Dan
                    Dan, my own lathe has a belt drive head too. But I never thought of using the belt drive as a clutch. I suppose it would work but it's not really a good option for me as the belt tensioning lever is directly behind the chuck. To use it as a clutch I'd have to get in close to the spinning work with both my chest and arm and it would be just asking to go for a ride. First on the lathe and then right after that in an ambulance... or more likely a hearse....

                    Sounds like if I were to go for any sort of upgrade that the hot setup is a 3ph motor and a VFD with the right sort of features.
                    Chilliwack BC, Canada

                    Comment


                    • #11
                      Originally posted by BCRider View Post
                      When I watch videos of the big iron lathes and even the similar size lathes to what I have but which are more seriously intended for commercial shop use I see that the common setup is a motor that starts and runs constantly for the whole time and that the lathe is clutched in and out and often has a brake built into the action of the clutching handle. (Edited- WOW! that was a long sentence!)

                      I'm just wondering if anyone has modified their "home" lathe to add such a clutch and perhaps the brake as well.

                      Seems like it would make things a lot easier on the poor motor.

                      Or does the use of a 3ph motor and VFD effectively replace such a clutch and brake setup?
                      Although most big lathes do have a mechanical clutch, a few have direct drive, that is starting the motor starts the spindle(chuck). In the big shop where I spent most of my years, they had a big Axelson, 40" swing x 16' between centers that used the electronic start(direct). When you had something big, like a two ton roll, the lights would dim momentarily when starting. In the summer, when it was hot and doing a lot of starting and stopping, we had to open the electrical cabinets of the power supply and set a big fan with it blowing in, to keep it cool enough so as not to overload the circuit breakers.

                      Sarge41

                      Comment


                      • #12
                        Originally posted by Doozer View Post
                        On a big lathe (or any lathe, really), one should spin the chuck one revolution
                        to just check if anything is going to hit or make contact with part of the lathe.
                        Not so much a problem with shafts, but odd shapes like castings is where this
                        step becomes most important. Also good to start an odd shaped piece gradually
                        to check for imbalance.
                        With a friction clutch, the user had direct control of the speed and torque that
                        gets applied to the chuck. With a VFD, you hit the button, and you are committed
                        to the motion that it is programmed to give you, unless you hit the stop button.
                        With a clutch, the control is all right there, instantly. Any sense of something
                        going wrong, the user can back off the clutch lever in an instant. Much quicker than
                        hitting a stop button. This is why a clutch is always better for a manual lathe.
                        The variety of work is so large, and no one wants to roll a 200 pound chuck and
                        probably much heavier workpiece over by hand to check for interference.
                        A VFD just can't do that.

                        -Doozer
                        Cant you add a knob that adjusts the speed on the VFD? Its an option on mine I think. JR

                        Comment


                        • #13
                          Way back HSM mag had a cover story about this very thing. A method of slacking the drive belt while keeping the lathe motor running.

                          I thought it was a dangerous thing. When I called the then editor he said everything they publish is passed through an engineering office across the street for review and they saw no fault with the idea.

                          It was like two or three issues later the mag, more or less, issued a retraction of the idea. Apparently I wasn't the only one who it was a stupid idea the way it was implemented.

                          Comment


                          • #14
                            I dimly recall that some motors have a specification for how many start/stops they can take in a given time. In those cases it might be better to have a clutch of some sort if you will be doing steady production work.

                            A collet closer that works while the spindle is turning is about as dangerous as a mechanism that loosens the belt. On the 9x20 the idea is that the belt life is extended by having it loose when you start the motor, then the lever is thrown to tighten it. It's not meant as a clutch to allow changing work in the chuck while the motor is spinning.

                            Dan
                            At the end of the project, there is a profound difference between spare parts and left over parts.

                            Location: SF East Bay.

                            Comment


                            • #15
                              I like my 10" lathe with DC motor. JR

                              Comment

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