Bar feeders, once known as slow and inefficient ‘rattle tubes,’ are now high-speed, automated units.
Ask any hand screw or screw machine operator the meaning of the term “rattle tube” and you’ll likely get an earful. Of course, you’ll probably have to shout, because he’ll be hard of hearing.
Rattle tubes, or pneumatic or pulley-drive bar feeders, are great at pushing bar stock into the back end of a lathe or screw machine, but they’re also noisy, dangerous and prone to breakdown.
The reason rattle tubes get such a bad rap is that, even though the bar stock is contained inside a tube, it’s still left unsupported along its entire length. As the bar spins, centrifugal force pushes it against the side of the tube, which not only makes a racket but creates vibration—never a good thing when machining.
But rattle tubes are mostly a thing of the past, having been replaced by far more effective solutions. Hydrostatic and hydrodynamic bar feeders and short-bar loaders are elegant, reliable alternatives.
Say your boss has grown tired of hearing the airplane-like roar of that 1 “-dia. bar stock spinning at 2,000 rpm and wants you to get more production out of a new CNC lathe, or your customers are complaining about poor part surface finish because you can’t get decent speed on your bar feeder and lathe without setting off car alarms. What can you do?
Tell your boss to get out his checkbook. Even a low-cost hydrodynamic bar feeder is $8,000, not to mention the cost of installation, spindle liners, guide bushings and an interface to the machine tool.
However, the expense will be justified by the equipment’s ability to increase machine output, enable cutting tools to impart finer surface finishes and improve tool life—all because a bar feeder lets you achieve the correct cutting speed for the workpiece material. Better yet, you won’t need hearing aids later in life.