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  • #16
    I guess I should read the manual for the drive. Electricity is not my strong suit and I was so happy it actually worked that I didn't probe much further.
    I was exaggerating on the blue chip thing. If I could take a 40 thou cut through mild steel Id be pretty happy, even if the feed rate was slow. The chips I was getting on the old lathe looked like R2D2's pubic hair.

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    • #17
      Originally posted by Commander_Chaos View Post
      I guess I should read the manual for the drive. Electricity is not my strong suit and I was so happy it actually worked that I didn't probe much further.
      I was exaggerating on the blue chip thing. If I could take a 40 thou cut through mild steel Id be pretty happy, even if the feed rate was slow. The chips I was getting on the old lathe looked like R2D2's pubic hair.
      Shoot. Even a decent Atlas 10", probably even a 618, should easily do 40 thou in mild steel. When you start to get into 4140 prehardened, then you begin to separate the hobby stuff from more "real" machines.

      What kind of machine do you have now that only cuts tiny "pack thread" chips?
      1601

      Keep eye on ball.
      Hashim Khan

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      • #18
        Originally posted by Commander_Chaos View Post
        I have a VFD on my milling machine and for that I did away with the stock forward/reverse switch. In addition to the power issue I really dislike the waiting for the machine to stop so I can change cutters. Could I set this up so that the VFD is wide open all the time?
        If you mean running the VFD on normal speed and reversing the output phases with a multipole switch on the run.. that aint gonna end well.

        But if you select enough beefy VFD and brake resistor you can brake, accelerate and reverse almost as fast as "banging" the 3-ph supply phases with switch. Motor overheating is going to be your limiting factor if you do it really frequently, with VFD heating problem is lessened.
        I have 1.5kW 3-ph motor on my bench drill and 5.5kW DTC drive VFD
        VFD lets me brake with 200% nominal torque if needed. (Probably even more than that if I just cheat on the motor specs configured to the VFD)

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        • #19
          Originally posted by Commander_Chaos View Post
          Well, like I said I'm going to see how I feel about the 1HP before I change anything, although I've become obsessed with seeing a big, blue chip curling off a piece of steel

          If I decide to go for more power I can move the 1hp motor and the VFD over to my bandsaw. Having speed control there would be pretty sweet.


          All of the 1.5 British ponies pushed to the limit and beyond on 11x24 Kerry

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          • #20
            If the lathe has a threaded spindle, no plug stopping or electronic braking allowed.

            RWO

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            • #21
              Originally posted by RWO View Post
              If the lathe has a threaded spindle, no plug stopping or electronic braking allowed.

              RWO
              Why ever not?

              D'tou expect the chuck to unscrew and go rolling around in the shop knocking thing over?

              I have HAD the chuck unscrew, it was several passes into making an 8 tpi thread when running in reverse.... and there was nothing dramatic about it, nor did it unscrew easily. It just unscrewed a bit and jammed the tool, I turned off the machine immediately.

              The chuck is not perilously loose on the spindle, it normally is quite reasonably tight, as you can see from the fact that it took several passes of 8 tpi threading to unscrew it. IIRC, I backed out the tool, spun the chuck on harder, and finished up. I did take a bit lighter cut.

              The amount of deceleration force involved in a chuck without a very heavy workpiece, is minimal. It just is not guaranteed to come flying off, as it is often portrayed when people give solemn warnings about the matter.

              This is not to say that a cam-loc or long taper mount is not better.... it surely is nicer in many ways, but you can have a reasonable amount of braking even with a threaded chuck. Just do not expect quarter-second stops (not that you'd get that even if you tried).
              Last edited by J Tiers; 03-05-2019, 02:40 PM.
              1601

              Keep eye on ball.
              Hashim Khan

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              • #22
                Originally posted by J Tiers View Post
                Why ever not?

                D'tou expect the chuck to unscrew and go rolling around in the shop knocking thing over?
                Believe me you don't want that at any higher speed

                6" 3 jaw come loose when I was running lathe back and forth when threading.. seeing the 6" chuck to unscrew itself, drop to lathe bed and jump to floor where your toes were 0.01 seconds ago gives sudden motivation for rapid improvements in chuck retention.

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                • #23
                  Originally posted by J Tiers View Post
                  What kind of machine do you have now that only cuts tiny "pack thread" chips?
                  I sold it Saturday but it was a 1928 South Bend 9" Junior with the original motor.

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                  • #24
                    Originally posted by J Tiers View Post
                    Why ever not?. . .
                    Because everything but threading is done at much higher RPM, and chuck inertia alone is enough to unwind it in a small fraction of a second.

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                    • #25
                      I wasn't really looking to do braking with the VFD, I just don't like that it seems to be under power the entire time it's spinning down. It would go faster if the power were just cut and it coasted to a stop.

                      Another hypothetical: what if the brake was on the chuck rather than the spindle?

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                      • #26
                        Originally posted by Commander_Chaos View Post
                        I'm ordering a VFD for the lathe I just bought and was surprised to see that even though it's a 13" it only has a 1 hp motor.

                        What would be the disadvantage, and I'm not actually going to do this, of putting a single-phase motor on it? 1 hp single-phase motors are readily available.
                        My Sheldon EXL came with a factory 1PH motor. It shook like a paint mixer. 1PH motors do that. If I want smooth drives, I want 3PH or DC. I went with 3PH 1 HP motor for my Sheldon and an Automation Direct VFD. Couldn't be happier. It has all the advantages others have mentioned plus JOG and RPM. 1:10 JOG comes in handy when you need to mesh QCGB or Reverse gears without grinding them.

                        Best Regards,
                        Bob

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                        • #27
                          Originally posted by rjs44032 View Post
                          My Sheldon EXL came with a factory 1PH motor. It shook like a paint mixer. 1PH motors do that. If I want smooth drives, I want 3PH or DC. I went with 3PH 1 HP motor for my Sheldon and an Automation Direct VFD. Couldn't be happier. It has all the advantages others have mentioned plus JOG and RPM. 1:10 JOG comes in handy when you need to mesh QCGB or Reverse gears without grinding them.

                          Best Regards,
                          Bob
                          My friend's Sheldon 14 shakes, but the motor has a bent shaft and the pulley is welded to it. I think he should fix that.

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                          • #28
                            Originally posted by Commander_Chaos View Post
                            I wasn't really looking to do braking with the VFD, I just don't like that it seems to be under power the entire time it's spinning down. It would go faster if the power were just cut and it coasted to a stop.

                            Another hypothetical: what if the brake was on the chuck rather than the spindle?
                            That was true for me. I did just that with my VFD because the default ramp was too slow. I set it to coast and it stops very quickly now. Hope this helps.

                            Best Regards,
                            Bob
                            Last edited by rjs44032; 03-05-2019, 04:34 PM.

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                            • #29
                              Originally posted by chipmaker4130 View Post
                              Because everything but threading is done at much higher RPM, and chuck inertia alone is enough to unwind it in a small fraction of a second.
                              This make my BS meter peg and bend the needle.....

                              1) "much higher rpm" Suppose you run 2000 rpm.... now, you are not gonna do that with anything large, because the SFM will be stupid a 4" part at 2000 rpm is way way faster than any tooling can take, never mind the power required to make a cut.... You could argue 4" aluminum at 600 rpm, but even that is a stretch, and unlikely with any older threaded spindle machine, the power is just lacking. Even a 1" diameter part is going to be at a pretty high SFM running 2000 rpm, somewhere around 500 SFM..

                              2) "Small fraction of a second".... With a small workpiece, like 1", a reasonable speed for 250 SFM is 1000 rpm, and that is a carbide type SFM. That is 16 rps.... so, if the spindle stopped instantly (which it would not) and the chuck absolutely did not slow down at all (but it would) then you could spin off a chuck in a half second or so, Not a "small fraction".

                              3) At faster speeds, the more likely workholding is a collet, and they do not unscrew like a chuck theoretically could.

                              4) It is often hard to get the chuck off the spindle, never mind it coming off easily at the drop of a hat, as many tend to suggest. It tends to take a pretty good yank to break it loose.
                              1601

                              Keep eye on ball.
                              Hashim Khan

                              Comment


                              • #30
                                Originally posted by J Tiers View Post
                                2) "Small fraction of a second".... With a small workpiece, like 1", a reasonable speed for 250 SFM is 1000 rpm, and that is a carbide type SFM.
                                It might feel like small fraction of second when your brain is trying to comprehend what is going on
                                Going from 220rpm forward to 220rpm reverse unscrews the chuck at 440rpm.. ask me how do I know.
                                ---
                                And ackchyually 250 SFM is still snail speed.
                                Been taking finishing cut on a 3" steel workpiece at 1500rpm more than once and that is still below! recommended starting values for the particular inserts (1200sfm on steel)

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