Fig. 30. Turret and Head of Jones & Lamson Double-spindle Flat Turret Lathe
Double-spindle Flat Turret Lathe.—The extent to which modern turning machines have been developed, especially for turning duplicate parts in quantity, is illustrated by the design of turret lathe the turret and head of which is shown in [Fig. 30]. This machine has two spindles and a large flat turret which holds a double set of tools, so that two duplicate castings or forgings can be turned at the same time. It was designed primarily for chuck work and can be used as a single-spindle machine if desirable. When two spindles are employed for machining two duplicate parts simultaneously, considerably more time is required for setting up the machine than is necessary for the regular single-spindle type, but it is claimed that the increased rate of production obtained with the two-spindle design more than offsets this initial handicap. The manufacturers consider the single-spindle machine the best type for ordinary machine building operations, regardless of whether the work is turned from the bar or is of the chucking variety. On the other hand, the double-spindle type is preferred when work is to be produced in such quantities that the time for setting up the machine becomes a secondary consideration.
When the double-spindle machine is used as a single-spindle type, a chuck 17 inches in diameter is used, and when both spindles are in operation, two 9-inch chucks are employed. The general outline of the turret is square, and the tools are rigidly held, with a minimum amount of overhang, by means of tool-blocks and binding screws connected with the clamping plates. Two duplicate sets of tools are clamped to each side of the turret and these operate simultaneously on the two pieces held in the chucks or on faceplates. Primarily the turret is used in but four positions, but when a 17-inch chuck or faceplate is employed, corner blocks may be held by the clamping plates in which tools are supported, giving, if necessary, four additional operations by indexing the turret to eight positions.
Fig. 31. Diagram showing Tool Equipment and Successive Steps
in Machining Sprocket Blanks on Double-spindle Flat Turret Lathe
A typical job to demonstrate the application of the double-spindle flat turret lathe is illustrated in [Fig. 31]. The parts to be turned are sprocket wheels which are held in the two 9-inch chucks. At the first position of the turret (which is the one illustrated), the inside is rough-bored by tools A. At the second position of the turret, tools B rough-face the inner sides of the flanges; tools C face the outer sides of the flanges, while tools D turn the faces of the flanges. At the third position of the turret, tools E finish-turn the inside of the flanges; tools F finish-turn the outside of the flanges, while tools G finish the faces of the flanges. At the fourth position of the turret, tools H finish-bore the sprockets; tools I complete the turning on the outside of the flanges, while tools J accurately size the interior of the flanges.