AN ADAPTABLE TYPE OF MACHINE
 Plano-Miller |
Combination types of piano-millers are manufactured to increase their range of usefulness. The Darling and Sellers' machine of this class is excellently designed for heavy work, whether used open-sided, or with the arm supported by the outer upright. The view (fig. 1) will suffice to illustrate its special features. It shows the machine arranged for ordinary work, with the detachable upright in position. This can be removed, leaving the arbor still supported at its outer end by a sliding stay fitting on the arm, and the machine is then ready for open side work, using a horizontal cutter.
The semi-parabolic shape of the arm carrying the arbor stay upon it are good points in this design, superior to the usual methods. The latter generally take the form of a round bar, in the fashion of Lincoln millers, connecting the head and stay, or that of a bracket sliding on, and bolted to, the face of the removable upright. In the Darling and Sellers' design, the alignment of the stay is ensured by sliding it along the arm. As the latter is firmly bolted to the head, clamped to the main standard, and is of the best theoretical form for withstanding the bending stress imposed upon it when used open side, the result is a very rigid structure.
Another point is that there are separate counterbalances for the main head, and the arm with its stay, so that when the arm is removed bodily for open side face milling, the headstock is still perfectly in balance for easy vertical adjustment.
By a special device seen on the front side of the machine, the objectionable and dangerous feature of sudden and very rapid rotation of the large hand adjusting wheels, when the quick power motion to the table is set in operation, is absolutely prevented. The hand wheel in question is clutched to its shaft, and the clutch can only be engaged when the belt operation lever of the power motion is in its central, or idle, position.
The gears are all protected with hoods, and the controlling handles are brought to the front side within easy reach of the operator. The graceful outlines by which the very substantial build of the machine is somewhat masked are noticeable, as is also the great proportion of depth to width of the bed. The machine, which weighs 5 tons, is capable of milling a length of 7 ft., it will clear 1 ft. 8 in. between standards, and a depth of 1 ft. 6 in. under the cutters, which are 4 in. in diameter. The cross slide will permit of a cutter up to 10 in. diameter clearing under it. The cutter arbor measures 2¼ in. diameter. The feed can be varied from 3/8 in. to 6 in. per minute.
THE CUNLIFFE AND CROOM PLANO-MILLER
Messrs. Cunliffe and Croom, Ltd., make a small piano-miller admitting 24 in. between the uprights. It is a stiff little machine on standards, and the spindle driving gear is exceptionally large. The spindle has a lateral adjustment, which enables the cutters to be put into position after the work has been fixed on the table. The table drive is through worm gear, and a screw with a disengaging clutch. There is an automatic disengaging motion, and a quick return by power by means of fast and loose pulleys, and mitre gears at the end of the screw at the back of the machine.
MACHINES BY KENDALL AND GENT
 Horizontal Plano-Milling Machine |
A machine by Messrs. Kendall and Gent, of Manchester, is shown in fig. 2, being a piano-miller with horizontal spindle. This particular example is the smallest size made in this type by the firm, the length which can be milled being 6 ft. It is of solid build, weighing 135 cwts. Its substantial character renders it specially suitable for the work of the locomotive and marine engineers, besides that of a general class. Milling the flat sides of links, the webs of levers valve and coupling rods, is generally more economical than planing them Narrow edges are milled in quantity by arranging the pieces side by side, and using a broad cutter wide enough to cover the lot.
The machine is so designed that a gang of cutters can be used to operate on work as wide as the table at one traverse. The two adjustable brackets on the cross slide permit of variation in the length of cutter arbors, and afford them ample support at the intermediate position, as well as at the end. A three-speed cone pulley, with back gears provides six speeds to the spindle. The cross slide is raised and lowered by the cross handle, in planing machine fashion, and is counterbalanced, portions of the supporting pitch chains being seen behind. There are six feeds to the table, which is screw driven. The rates of feed are read off on an index pulley. A vertical spindle attachment—seen on the ground —fits on the cross slide, to be used for edge milling.
AMERICAN DESIGNS
 Heavy Slabbing Milling Machine |
 Heavy Slabbing Milling Machine |
American designs are numerous in this tvpe of machine. Illustrations (figs. 3 and 4) of the productions of the amalgamated Niles-Bement Pond Company are given. Another firm making a specialty of these heavy types is that of Beaman and Smith, of Providence, R.I. These are manufactured with spindles ranging in number from one to four. Some have two housings, some are open-sided, others have one housing, removable at pleasure.
A favourite form of open-side machine by this firm is that in which an upright is bolted to one side of the bed. Upon it slides the overhanging arm, its vertical adjustment being provided by a screw which is supported on a ball bearing. A saddle has horizontal movement along the arm, automatically fed in or out with a stop for each direction of movement. The spindle is carried in a head, adjustable vertically. The driving power is derived from a four-stepped cone through back gear, providing six cutter speeds— from 10 to 114 revolutions per minute—suitable for cutters ranging from 12 in. to 1 in. diameter. The table feed, which is screw driven, ranges from 1 in. to 8 in. per minute, for any speed of the spindle. The feed of the saddle which carries the spindle head is from about A in. to 4 in. per minute.
Another open-side machine carries two vertical spindles, each with independent vertical and cross adjustments. The arm has vertical adjustment by a screw with a graduated dial. In other cases the overhanging end is supported on a bracket, or housing.
A MACHINE THAT MILLS EIGHT FACES SIMULTANEOUSLY
 Special Milling Machine |
A very special milling machine is illustrated in fig. 5, by Messrs. John Hetherington and Sons, Ltd., of Manchester, designed for the London and North-Western Railway Co., for finishing at one operation eight faces on the quadrants, one of which is seen on the ground. It will be observed that one of the heads is carried on a hinged swinging bracket, which is thrown open, as seen in the illustration, when the work is being inserted. The quadrant to be tooled is gripped in a chuck on the rising and falling table, this motion being imparted for the feed. The act of closing up the swinging front brings the bevel
wheels into gear, so that all the cutters operate at once. The self-acting feed being also put in the casing is fed against the cutters.
The advantage which such a machine possesses over a planer, shaper or slotter, lies not only in the fact that so many faces are being tooled simultaneously, but also in the uniform size and shape of all the castings operated on.
MILLING ON A PLANER
Not much has been done as yet in adding milling appliances to other machines, though various machines are designed to combine milling with drilling, boring, or turning. The Adams Company, of Dubuque, Iowa, have a fitting which can be attached to any planer, converting it into a true milling machine, capable of doing everything that can be put on a plain miller.
The machine comprises two brackets which tit on the planer cross rail, one of which carries the spindle and its driving gear, the other the tail support. The operating gears are belted from a countershaft distinct from that of the planer. The spindle can be swivelled anywhere from vertical to horizontal, and a belt tightening device takes up or lets out slack to suit the different positions. The change from planing to milling, and
vice versa, can be made in a few minutes, so that the proper work of the planer is not stopped for any length of time by the rigging up of the milling head. There is also the advantage that work can be roughed out by one method, and finished by the other when desired, without having to reset it on different machines.
One of the later developments in milling is that of cutting worms and screw threads in machines of special construction. These have some advantages over single cutting tools, but can only be utilized economically when there is a constant run of this class of work.
CONCLUSION
We have now traced the growth of the milling machine through many phases, from the original Lincoln of light construction, employed only in some special industries, to the diverse and heavy types which are now indispensable in all modern engineers' shops. There is not the slightest doubt that many other developments will grow out of these, as the practice of milling grows, and as firms specialize accordingly.
Information Sources
- Page’s Engineering Weekly Milling Machines Part Viii by Joseph Horner, Vol. 2, Feb 1903 pages 126-131