What is a Vertical Boring Mill?

One of the largest machine equipment manufactured today is the vertical boring mills. It is chiefly used for turning, facing or boring large work pieces that are shaped symmetrically. Because of its design, circular cuts can only be made as the work is rotated against the fixed tool. Applications for vertical boring mills are machining large steam engine turbine casings, ring gear blanks, locomotive tires, water turbine runners, flanges for large pipes and machine tool tables. The rotary table houses the mechanisms that drive it and sits on the bed. Two vertical uprights are mounted to the back of the diameter of the table, which bolsters a cross rail. The cross rail can be moved up and down on the support columns in order to lodge various work pieces. It also has one or two tool heads mounted on it as well as each vertical upright. For smaller mills, there is usually one turret head and one heavy boring bar that tilt at different angles. For larger mills, the turret head and swivel bar are replaced by two heavy boring rams to supply vertical feed of the tools.

The main parts of the vertical boring mill are as follows:

-         Bed - A circular, hollow unit that is the main casting of the machine. It covers the spindle and the bevel gear and pinion which drives the table.

-         Table - A circular shaped casting mounted on top of the bed and is rotated through gearing. It is the work holding part comparable to the lathe's head stock and faceplate.

-         Housings - two vertical members which support and rise from opposite sides of the base. The faces of the housings are finished in order to furnish bearing surfaces for the cross rail.

-         Cross rail - a rectangular casting mounted on the housings to stay parallel to the surface of the table. It's counterbalanced and can be raised or lowered to accommodate various work pieces.

-         Saddles & Tool heads - normally VBM's have two saddle and toolhead assemblies on the cross rail. They're maneuvered across to feed the cutting tools parallel to the table. The motion of the tools creates plane surfaces.

-         Rams - Similar to the cross rail, the rams are counterbalanced to aid movement in their bearings. The rams can be maneuvered vertically in their toolheads to feed cutting tools at 90 degrees to the surface of the table. The motion of tools generates cylinders. Arch - connects the housings at the top and maintains rigidity to the structure of the machine.

When selecting a machine to suit the production requirements, the user should consider a vertical boring mill over a standard lathe for several reasons:

-        Operating a work piece that is too large or heavy to be handled on a lathe,

-        Turning, facing and boring operations on various work piece sizes for maximum machine flexibility,

-        Work which necessitating during setup,

-        Counterbalancing irregular or off-center workloads for high speed turning

When the user has chosen a vertical boring mill best for his production needs, he should also consider other available features.