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Jet 13/40 Belt drive

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  • Jet 13/40 Belt drive

    Jet makes a 13/40 Belt drive lathe.It has an independent lead screw and feed rod.What is the advantage of this design? With reference to gap beds, how many of you with this type ever remove the bed insert and how accurate is the reset. I am sure its ground with the insert inplace? Any input on this lathe in comparison to the Griz G4003G greatly appreciated.

  • #2
    The independent feed rod reduces wear on the lead screw threads, powering the carriage for everything but threading. This makes the threads and 1/2 nuts last much longer. I don't think many people remove the gap. When I did, it was a pain to get it back in correctly. Can't help you on the comparison.


    • #3
      They shim the gap inserts with bubble gum for alignment before grinding.

      Get in a stock of Double Bubble before re-installation and you should be okay.

      Yeah, I'm joking, but not far off from the truth. I suggest not removing the gap on cheapo lathes.


      • #4
        Actually, other than the smallest/cheapest lathes, most of the better quality (and many of the cheaper) machines do not use the lead threads or half nuts to drive the carriage, even if they have no feed rod. In most cases, there is a keyway down the lead screw that is used to drive a worm inside the apron, which in turn provides the power feeds.

        The only real down side of this is that the simplest/cheapest of these (used in all the smaller Chinese machines I've seen) just run a straight key in a straight keyway. This can raise burs on the lead threads as well as leading to swarf packing/abrasion in the threads, both of which increase wear on the half nuts and threads. Better ones use different methods to avoid that situation. For instance, Rockwell made the key slot like a "T" so that there is always a gap between the driven key and the ends of the threads. Issues from the keyway, particularly if not kept reasonably clean (or using the simple/primitive design found on some small imports), still can lead to reduced lead life, but not like some of the old Atlas (and other) lathes that used the half nuts for standard feed.

        So a separate feed rod is an improvement, but not a huge issue for most HSM uses.
        Master Floor Sweeper


        • #5
          Lilguy, I have a Jet 13x40 belt feed lathe. I bought it about two years ago and so far I have been very happy with it. When I set up my shop my primary goal was to build model engines and I wanted a lathe that would cut very straight so I could do the pistons and cylinders with out to much trouble. It does an excellent job. Also, the latere models have an enclosed feedbox which keeps the gears in a constant oil bath. Also, I don't mind jumping belts on it to change speeds because it is relatively easy to do and is super quiet to run. One day I'd like to install a 3 phase motor and VFD.
          Jonathan P.


          • #6
            For all around use, would one be better than the other? Jet 1340 belt or G4003G?


            • #7
              One thing I would encourage you to look at if you can is the need for change gears. Often, lathes in this size range require them. Some (typically larger) lathes require no change gears at all. Others use them, but have the convenience of handling all or most of the feeds and all or most of the inch thread pitches with the same set of gears mounted.

              I have a Kent 1340A which is the same as the Grizzly G9036. It covers all the feeds with one gear set, but changing to threading requires a change...and then back again. This can be annoying if you are making a bunch of parts where you want to turn to the major diameter using the power feed and then thread each piece. In the end, you end up either manuall feeding all of the turning or just use a power feed rate that is no where on any chart but looks about right, because you have the change gear set mounted for threading. Power feeding still works, but the chart becomes meaningless and often the rates of feed available are pretty high.

              I have a copy of the G4003 manual in .pdf off the web site since I considered that lathe before I bought the one I have. It says:

              "While other thread pitches may be achieved, the G4002/3 comes with a chart that requires no gear changes for cutting inch threads"

              If I read that correctly, you can do feeds and inch threading with the same gears mounted....pretty handy.

              I went with the lathe I have for a variety of reasons. It has an oil bath feed/threading gear box rather than an open one which I figured might add longevity. Its also a bit larger than the G4003. On the other hand, it appears that I compromised some convenience for that. Having used the G4003's they have downstairs here at work, they are a good lathe.

              In any case, it something you may want to consider if you can find similar information for the particular Jet lathe you are looking at.

              Paul Carpenter
              Mapleton, IL


              • #8
                Its been 25 years since I was a lathe operator. Want to get back into it on a smaller scale now. I have been looking at Jet for a while. Their 13/40 belt or gear heads have some features that the G4003G doesn't. Also the Jet has hardened gears, and a 2 year warrenty.If you would not mind looking at the on line Jet specs I'd appreciate you opinion.


                • #9
                  The jet 13x40 lathe that I have can feed and then turn a few dials and you are threading. There is a few threads that you may have to change a gear to cut but most of them use the standard gearset. I like it a lot as I said before. If you have any more specific questions about the Jet feel free to ask.
                  Jonathan P.