Years ago, before CNC machines came on the scene, if you needed a very high accuracy boring mill to machine the large side frames of a printing press, or the frame of a paper making machine, or a plastic laminating machine or the pin holes of a die or mold set, your only choice was a DeVlieg Jig Mill. These where the only machines made with the travels and accuracy to bore multiple holes in a side frame of one of these kinds of machines that have many rollers mounted in bearings or journals that need to be aligned nearly perfectly with each other. A well maintained DeVlieg can position with an accuracy of just one tenth per foot over a large distance permitting the kind of precision required for these parts. Today, this work is commonly done with CNC boring mills that have scales and position feedback systems that can achieve this kind of accuracy and repeatability relatively effortlessly. As a result, the DeVlieg is a machine that has fallen out of favor of late, and can be bought for far less money than they once sold for. Today, they are a highly cost effective solution for many shops.
While DeVliegs are no longer used much in production situations, many have found homes doing high-quality repair work and low volume production. The cost is so low for a DeVlieg today that it pays to consider it as a low priced alternative to an extremely costly large capacity CNC machine or a cheap, far less accurate horizontal boring mill. While a DeVlieg is limited by its relatively short spindle and saddle travels, it is no more limited than the typical CNC horizontal machining center of similar X and Y travels. One of the benefits of a DeVlieg is that it can bore holes in one side of a part, which can then be indexed so the DeVlieg can bore near perfectly lined up holes on the other side of the part. DeVlieg made accessory rotary tables called the E type that due to its simple, foolproof design can index 90 or 180 degrees and lock with near perfect accuracy. Very large CNC machines generally do not have index tables (unless they cost over $1 million), but on a DeVlieg, a large index table can be added for very little money, comparatively speaking.
While many older horizontal boring mills have morse taper spindles, all DeVliegs are equipped with modern milling machine tapers and power draw bars. DeVliegs were made in sizes from 2.5 spindles all the way up to 6 spindles. DeVliegs dont have saddles, like horizontal boring mills have, to move the table further and closer to the spindle, but they do have platen travel, which accomplishes the same effect but with much less travel, usually. Spindle travels in and out are shorter on a DeVlieg than on a similar size horizontal boring mill this is because of the accuracy requirements typically expected of DeVliegs.
Most DeVliegs do not have hardened ways, they almost always have soft, flaked ways that can be rescraped as needed to return the machine tool to its original accuracy. While rescraping is costly, it is a fraction of the cost of taking apart a hard way machine to regrind the ways this is a major rebuild requiring the machine to be out of service for months and shipping to the rebuilder than reinstalling in your shop. A DeVlieg can be rescraped on your floor in a few days.
DeVliegs have it all over horizontal boring mills of similar age in the department of operator controls. DeVliegs have dial speeds and feeds, no levers like most old time boring mills. Between the push button power draw bar and the dial in feeds and speeds, the DeVlieg is a much easier machine to operate and much faster.
The DeVlieg is made for accuracy. The table is fully supported on the base the full travel left to right. A boring mill table rides on a saddle that most often runs well off the base from side to side, and accuracy can suffer accordingly. Some higher quality boring mills have outriggers set in the floor on both sides of the base to support the saddle when the table runs out to either side. While this does achieve better rigidity, the accuracy is only as good as the level and condition of the outriggers and they, being separate pieces from the machine, need to be installed and leveled on their own, making for a much more complex install than with a one-piece DeVlieg.
Today, the one of the best things about a DeVlieg is their price. A 3 DeVlieg from the 1960s or 70s sells for around $10,000 to $15,000 in good shape, while a 3 horizontal boring mill of that age with power draw bar and milling machine taper (not morse taper) sells for around $25,000. This makes no sense the DeVlieg is a far better machine in almost every way. The DeVlieg will have just 16 of spindle travel and similar platen travel while the boring mill will have 24 of spindle travel and a bit more than that in saddle travel, other than that slight advantage, the DeVlieg is more machine in most every way, yet sells for half the price.
For my money, Id buy a 4 DeVlieg for the same cost as an ordinary 3 horizontal boring mill and have the best of both worlds. The travels of the 4 DeVlieg will be similar or greater than the 3 table type boring mill, and the many other advantages of the DeVlieg would be mine for a comparable price.