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  • Monarch 12CK increase top speed?

    Hello, I am new here, and to lathes as well. This is my first post, maybe another location would have been better to post in... all that not withstanding I am looking at a Monarch 12CK. The lathe was built in 1942 and has a top speed of 550. Is there a way to double or triple that top end? An acquaintance who runs a machine shop advised me that 550 is way to slow for smaller work, stating that it was fine for 4" diameter and larger but would leave smaller work rough.

    Thanks for any advice on speed adjustment,
    Jack

  • #2
    The Monarch CK is a first rate lathe; there are few better lathes built for general job and production shop service. You are retrofitting a lathe drive. As it exists now its max RPM is too slow for modern tooling and for small scale work. It needs to have the range of spindle speeds increased everal times. You wish to triple the spindle RPM. I can see no reason this cannot be done but if the lathe is to work well the new drive has to meet a certain standard.

    If the machine is all ball and roller bearing there's no reason why the s[pindle speed can't be pushed to 2000 RPM. The key is to re-pulley the machine enlargng the motor pulley and reducing the headstock pulley. Possibly replace the motor if it name plate RPM is low..

    Start this project with data collection: record the nameplate RPM of the existing motor, diameter of the motor pulley, diameter of the head stock pulley, condition of the seals and gaskets whose access is obstructed by the headstock pulley. Take pictures so you can put everything back.

    First look at the motor. If the motor is 1200 synchronus you might gain a good part of the speed increase by replacing the existing motor with one having 1800 sync RPM. That is, if there is a motor available within your budget. If you decide to downsize the motor go no smaller than 3 HP. 5 would be better.

    I think the Monarch CK headstock pulley has a lower limit for size because the clutch casting extends inside for a distance. Look at this then determine how much the pulley can be safely reduced. The lower limit would require that 1/4" or more metal remain between the bottom of the V belt grooves and the pulley's clearance ID. Bum a lathe and do it re-grooving it for V belts. The pulley may have to be re-balanced.

    Finally calculate the motor pulley diameter needed and either make or buy it. Remember that you are tripling the spindle RPM. That means you can drive the headstock with 1/3 the number of V belt originally supplied.

    Is your shop 3 phase? Have you considered a VFD? You can readly run a three phase motor to 1 1/2 times the name plate RPM just by increasing the max Freq parameter when setting up the VFD.

    Before assembly, make a precautionaty seal and gasket replacement and while you have it open look at the clutches. If the clutches are shot you may wish to replace them. Increasing the spindle RPM's places a greater demand on the headstock clutch when accellerating heavy chucks to the new max spindle RPM. You may wish to either replace the clutch wear parts or again consider a VFD and leaving the clutch permanently engaged. The VFD will start/stop/reverse the motor with little starting current surge thanks to its ramp to speed accel and decel features.
    Last edited by Forrest Addy; 05-21-2010, 09:05 PM.

    Comment


    • #3
      It all depends on the bearings and the lubrication system. One also needs to remember the 40's was when carbide cutting tools were just coming into use. HSS was not as developed than as it is today. Consequently cutting speeds were much slower as a lot of carbon steel cutting tools were still in use.

      You may be better off leaving the spindle speeds alone and just use HHS tooling.

      Comment


      • #4
        Lathe

        Another important item to consider is the RPM rating of
        the chuck being used. many chucks will open-up when RPM ratings are exceeded.

        JWR

        Comment


        • #5
          Jack

          You might check over on the Practical machinist forum, in the Monarch section. You'll find a ton of info with a little searching.
          I think the "CK's" could be ordered with a higher RPM rating in the 750 range.

          Hal

          Comment


          • #6
            The Monarch 12" CK is an all ball and roller bearing lathe. It weighs approx 3500 LBS, came with a 3 or 5 HP motor, your choice. The top speed offered from Monarch was 1200 RPM.
            My 12" CK, see Sept '04 HSM, "Reconditioning a Lathe-Revisited" for the reconditioning, has had it it's top speed doubled to 1400 RPM from 700 RPM. I strongly recommend that you not exceed 1400 RPM, although I've been thinking about lowering the top end to 1200, as 1400 is to fast for that lathe, and I've only been there a couple of times, in 7 years.
            The only parts of the drive system I would change would be the motor and its RPM, and the motor sheave, leave everything else alone. You will have to consider the opening in the base casting for the belt passage, when changing the motor sheave.
            BTW, they are very nice machines.
            Harry

            Comment


            • #7
              Originally posted by Forrest Addy
              The Monarch CK is a first rate lathe; there are few better lathes built for general job and production shop service. You are retrofitting a lathe drive. As it exists now its max RPM is too slow for modern tooling and for small scale work. It needs to have the range of spindle speeds increased several times. You wish to triple the spindle RPM. I can see no reason this cannot be done but if the lathe is to work well the new drive has to meet a certain standard.

              If the machine is all ball and roller bearing there's no reason why the spindle speed can't be pushed to 2000 RPM. The key is to re-pulley the machine enlarging the motor pulley and reducing the headstock pulley. Possibly replace the motor if it name plate RPM is low..

              Start this project with data collection: record the nameplate RPM of the existing motor, diameter of the motor pulley, diameter of the head stock pulley, condition of the seals and gaskets whose access is obstructed by the headstock pulley. Take pictures so you can put everything back.

              First look at the motor. If the motor is 1200 synchronous you might gain a good part of the speed increase by replacing the existing motor with one having 1800 sync RPM. That is, if there is a motor available within your budget. If you decide to downsize the motor go no smaller than 3 HP. 5 would be better.

              I think the Monarch CK headstock pulley has a lower limit for size because the clutch casting extends inside for a distance. Look at this then determine how much the pulley can be safely reduced. The lower limit would require that 1/4" or more metal remain between the bottom of the V belt grooves and the pulley's clearance ID. Bum a lathe and do it re-grooving it for V belts. The pulley may have to be re-balanced.

              Finally calculate the motor pulley diameter needed and either make or buy it. Remember that you are tripling the spindle RPM. That means you can drive the headstock with 1/3 the number of V belt originally supplied.

              Is your shop 3 phase? Have you considered a VFD? You can readily run a three phase motor to 1 1/2 times the name plate RPM just by increasing the max Freq parameter when setting up the VFD.

              Before assembly, make a precautionary seal and gasket replacement and while you have it open look at the clutches. If the clutches are shot you may wish to replace them. Increasing the spindle RPM's places a greater demand on the headstock clutch when accelerating heavy chucks to the new max spindle RPM. You may wish to either replace the clutch wear parts or again consider a VFD and leaving the clutch permanently engaged. The VFD will start/stop/reverse the motor with little starting current surge thanks to its ramp to speed accel and decel features.
              Thank you for the detailed instructions. The motor is a 5hp single phase, but I don't know the rpm. What is "VFD"?

              Thanks for all the answers.

              Jack

              Comment


              • #8
                Originally posted by Jack Wilson
                Thank you for the detailed instructions. The motor is a 5hp single phase, but I don't know the rpm. What is "VFD"?

                Thanks for all the answers.

                Jack
                Yes his instructions are quite good.

                A VFD is a Variable Frequency Drive usually used to convert single phase electric power to three phase. I'm not that familiar with them as I have chosen to stick with single phase on all my machines.

                However, if you search the forum you can find info on VFD's and I would also Google VFD or Variable Frequency Drives.

                You have acquired a very good machine. They were one of the lathes favored by the Navy and saw years of service on board ship and at shore installations.

                Comment


                • #9
                  Originally posted by Dr Stan
                  You have acquired a very good machine. They were one of the lathes favored by the Navy and saw years of service on board ship and at shore installations.

                  To be clear, I did not buy this machine, I am looking at it, and debating on two points, the low top end, and the shear weight of it, I know that's an asset, but its also a very strong deterrent for me, I don't know how to move it on either end of the trip, start to finish. Its tucked away in one mans shop, and would be tucked away in mine, and then in about a year I plan to move to a new larger shop so I get to go through it all, all over again!

                  Jack

                  Comment


                  • #10
                    Last spring, with help, I moved an early 1900's 9 foot Cincinnati planer 700 + miles to my home shop. About 4500 lbs for the frame and another 2000 lbs of table. Forklift in Baltimore, but none here.

                    Where there's a will there's a way.

                    Comment


                    • #11
                      I don't know if the article I referenced is still available from HSM, but I'm providing a link to very similar topics in the Monarch forum of PM. These are very long reads.
                      http://www.practicalmachinist.com/vb...update-146913/

                      http://www.practicalmachinist.com/vb...ew-toy-163406/

                      The lathe in the second link is the successor model to the C series that the OP is looking at. The construction of the Series 60's and the C Series are very similar. The 10EE in the first link, follows very closely the reconditioning sequence I used in the HSM article. The only I did to the 12" CK that is not covered in the 2 links, is the increase in the top end speed. I did change the motor from a 3 to a 5 HP, and changed the motor sheave for the higher RPM's.
                      Harry
                      Last edited by beckley23; 05-23-2010, 09:41 PM.

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