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  • #16
    Originally posted by dian View Post

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    That's a super nice mill. I have a Burke #4 and that looks huge compared to it. IMO that "little" mill will hog some metal.
    My mill has a 3/4 hp 4 speed gear motor and three pulley options. Still doesn't run slow enough so I put a vfd on it. Running it slow really limits the cutting torque. Maybe I have something set wrong but I've been told that this is expected when running a vfd at low rpm?

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    • #17
      Originally posted by challenger View Post

      That's a super nice mill. I have a Burke #4 and that looks huge compared to it. IMO that "little" mill will hog some metal.
      My mill has a 3/4 hp 4 speed gear motor and three pulley options. Still doesn't run slow enough so I put a vfd on it. Running it slow really limits the cutting torque. Maybe I have something set wrong but I've been told that this is expected when running a vfd at low rpm?
      When you do that you do not get the benefit of the torque increase that geared or belt speed reduction gives. So you are still getting the same motor torque as before, but at the cutter it is less than you would get if you reduce speed the conventional way.
      1601

      Keep eye on ball.
      Hashim Khan

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      • #18
        Originally posted by Doc Nickel View Post

        As to why, I don't know what specific machine you have, but generally speaking, most small horizontals, like the Burke, Nichols, old Pratt & Whitney, many Browne & Sharpes, etc. were intended for factory work, not necessarily general machining. Meaning you had a row of them all set up, and each would only make one cut per blank. The blank would progress through dozens of machines, each with a different fixture and cutter, emerging as a finished part at the other end.
        Doc.
        As Doc said many of those machines would be set up to do one specific cut. The machines could be ordered with many different options including speed ranges. So the machine would work for years till worn out and then be passed on to the machine dealer. You may have the option of changing the drive pulleys or the motor to get one of a different speed. The machine you picture is a bit different in that it has a leadscrew and an operating lever on the X axis. Is the lead screw to position the table and then use the handle to stroke the X axis?

        lg
        no neat sig line
        near Salem OR

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        • #19
          you can move x by turning the handle, by power or with the leaver.

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          • #20
            Larry_g, the machines you speak of have a single t slot often, not many features no bells and whistles, I have seen a couple. .
            this looks like a full on small horizontal mill....... some, on ordering have choice of speed range...
            Last edited by 754; 06-30-2020, 05:26 PM.

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            • #21
              our 60's vintage NC machine has a 16 speed gear box with the top speed of 2400rpm... With a vfd we eek out 3krpm but the bearings certainty get warm..

              This was the grandfather of cnc machines..

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              • #22
                Originally posted by challenger View Post
                My mill has a 3/4 hp 4 speed gear motor and three pulley options. Still doesn't run slow enough so I put a vfd on it. Running it slow really limits the cutting torque. Maybe I have something set wrong but I've been told that this is expected when running a vfd at low rpm?
                Think it has something to do with the relationship between HP and speed. Since HP=RPM*Torque, reducing speed means that even if the amount of torque the motor puts out remains the same, the amount of power it puts out decreases

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                • #23
                  I have a small horizontal mill, similar in size to Dian's. Mine is an Adcock & Shipley 1-ESG. It has a 40 INT taper, and a lowest speed of 25rpm.

                  Ian
                  All of the gear, no idea...

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                  • #24
                    Originally posted by epicfail48 View Post

                    Think it has something to do with the relationship between HP and speed. Since HP=RPM*Torque, reducing speed means that even if the amount of torque the motor puts out remains the same, the amount of power it puts out decreases
                    Well SOMEONE acknowledges this, which is an obvious fact often denied or blown off.

                    And the other side of it is that when slowing down by belts, or gears, the HP is preserved by the increase of torque at the cutting edge. So when NOT using belts etc, the power is significantly reduced, like a factor of 2 to 5 x, and so the "subjective" feeling of no torque, or, with treadmill motors, the complaint about "tiny chinese horses" is somewhat justified, but it is blamed on the wrong cause.

                    For the true cause, check the mirror.
                    1601

                    Keep eye on ball.
                    Hashim Khan

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                    • #25
                      Originally posted by dian View Post
                      i have a little 30-taper horizontal. the original speeds are 87 - 1000 rpm. why is there not a lower speed?
                      Is the speeds range you've posted, from a placard on the mill or your own measurement?
                      Is it possible that the original lower speed motor was replaced before you acquired the machine?

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                      • #26
                        Originally posted by reggie_obe View Post

                        Is the speeds range you've posted, from a placard on the mill or your own measurement?
                        Is it possible that the original lower speed motor was replaced before you acquired the machine?
                        A 40 rpm minimum would mean a max speed of 460 RPM. Possible, but not typical of smaller mills.

                        Small mills were probably often assumed to be used with tiny cutters, and so lower speeds were considered not required, because the assumed small cutters would reach suitable SFM at the higher rpm.

                        Whatever the reason, it seems to be a nearly universal assumption.
                        1601

                        Keep eye on ball.
                        Hashim Khan

                        Comment


                        • #27
                          Originally posted by J Tiers View Post

                          A 40 rpm minimum would mean a max speed of 460 RPM. Possible, but not typical of smaller mills.

                          Small mills were probably often assumed to be used with tiny cutters, and so lower speeds were considered not required, because the assumed small cutters would reach suitable SFM at the higher rpm.

                          Whatever the reason, it seems to be a nearly universal assumption.
                          Sorry, but the OP is exactly forthcoming on specs., make or model, so anything is possible. It could have been modified by a previous owner for a specific purpose.

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                          • #28
                            Originally posted by reggie_obe View Post

                            Sorry, but the OP is exactly forthcoming on specs., make or model, so anything is possible. It could have been modified by a previous owner for a specific purpose.
                            ?????

                            Yes, of course, but he HAS what he HAS, and apparently those numbers apply to it.

                            However, small mills are very often not provided with back gears to get lower speeds. It is not just his, it is often the case, especially with "me too" products. My horizontal mill had a very popular modification (back gears) added to it in construction. But the designer did not include that, presumably for the usual "it's just a small mill, doesn't need nothin like that" reason.

                            Small mills from makers of larger mills nearly all seem to have useful speed ranges. Perhaps they know something others do not?
                            1601

                            Keep eye on ball.
                            Hashim Khan

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                            • #29
                              Originally posted by reggie_obe View Post

                              Is the speeds range you've posted, from a placard on the mill or your own measurement?
                              Is it possible that the original lower speed motor was replaced before you acquired the machine?
                              yes, 87 is what it says on the mill. as i got it its close to 100 rpm, so even worse. sheaves are welded on and the sizes are maxed out anyway. the motor speed might very well not be original. i was just wondering, why they didnt go lower on the speed range with 12 speeds available.

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                              • #30
                                My 3hp Kempsmith has a 50 taper and has speeds from 18 to 575. I have the opposite "issue" that with the small collection of cutters I have I can barely get to recommended speed for aluminum for some jobs. I'm not doing anything time critical here, so I work around it.
                                Tom - Spotsylvania, VA

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