Old Wine, New Bottle
Too many of the latest generation of machinists are unfamiliar with multispindle automatic bar machines—screw machines—so they lump all of them together as "World War II Acmes." These machines may be old and obsolete, but there is value in the rapid, multispindle "screw machine" design. That concept is like old wine, and some machine shops are discovering how satisfying this old wine can be.
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Recently I read an article about the future of the precision machining industry. In the article, the head of a good-sized shop was quoted as saying "The future (of the industry) is not World War II Acmes." Of course, he's right . . . mostly.
Too many of the latest generation of machinists are unfamiliar with multi-spindle automatic bar machines—screw machines—so they lump all of them together as "World War II Acmes." Of course, those 30-, 40-, and 50-year-old machines, whether Acme, New Britain, Davenport, or something else, are not as sophisticated as CNC machines. These machines may be old and obsolete, but there is value in the rapid, multi-spindle "screw machine" design. That concept is like old wine, and some machine shops are discovering how satisfying this old wine can be.
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A CNC shop recently asked S&M Machine (Oconto Falls, Wisconsin) to compute the cycle time for one of its parts if made using our new screw machines. Its customer had boosted order quantities significantly. Its CNC machines were making the part in 40 seconds. Our multi-spindle machines, made new using "aged screw machine design" with many advances, will produce one part every 7 seconds by our estimate, within the part specs. This is what I mean when I say that old wine—this proven screw machine approach—can be satisfying. It's about proven processes using new tools.
S&M has been a manufacturer and remanufacturer for decades. A dozen years ago, S&M began producing new 1 1/4 inch and 1 1/2 inch six-spindle machines, part and tooling compatible with the New Britain Model 52. Last year, S&M introduced a 1 1/8-inch bar capacity eight-spindle machine. These machines combine the speed advantage of screw machine design with recent improvements in design, setup and control, and therefore are like old wine in new bottles.
The latest version of these screw machines is designed with variable speed AC motor drives for quick, fine adjustment of spindle rpm and the machine's feed rate. This advancement eliminates potentially troublesome clutches and brake, and the need to change gear sets to adjust the spindle rpm and machine feed rate. These drives quicken setup and eliminate the main drive belt. New, sealed spindles work to keep coolant out of the spindle carrier case and the lube oil inside the machine.
Those who lump screw machines together with the buggy whip may believe that today's tolerance needs are tighter than screw machines can deliver. One automatic bar machine strength has contributed to this misunderstanding—these machines generally last a very long time and are often used well past their prime. I know of a shop with six New Britains bought new in 1960. These machines have been running the same part family, with small changes, for more than 40 years. This is not uncommon. The price of such long life is reduced ability to hold tolerances—years of use erodes the precision of any metalworking machine, even one well maintained. Some machinists of today assume that every screw machine holds tolerance no better than the old, well worn units. That simply isn't true.
New machines, and used machines that have been completely remanufactured by a qualified shop, will hold the tolerances required on a high proportion of the work in most shops. Holding a couple thousandths is possible with these machines in the hands of a good setup person and dedicated operator. Old design, new iron.
With the availability of dual-axis CNC cross slides, new attachments, and new methods, screw machines produce more complex parts than before. New technology for old problems.
Value added services, holding tighter tolerances, and producing complex parts bring better margins. Screw machines fit that strategy. New machines; well maintained machines; well run machines. These are the new bottles holding the fine, old wine.
Old wine in new bottles—you bet.
