This second installment of our series looks at key machine-tool elements and addresses the tool, the toolholder, and machine control.
The cutting action in a machine tool when milling and drilling involves the spindle, toolholder, and tools.
Spindle Design
Spindles, which secure the tool and its holder, are key in determining machine tool accuracy. In early machine tools, the spindles were simple bearing-- mounted shafts driven by a constant-speed electric motor, achieving different speeds through belts and gears. Operators changed spindle speed by shifting gears or moving belts to and from various pulleys.
As drive motors achieved higher torque and were designed to operate at variable speeds, belt and gear-driven systems began to wane in popularity, but both are still used. Stronger, longer-wearing, quieter belt and gear-- drive designs have been developed. Variable-speed direct drive, or integral-- motor spindles have replaced geared spindles for high-speed applications. At the same time, spindles with planetary gear systems, much like a car's automatic transmission, are now used to provide a wide torque output.This second installment of our series looks at key machine-tool elements and addresses the tool, the toolholder, and machine control.
The cutting action in a machine tool when milling and drilling involves the spindle, toolholder, and tools.
Spindle Design
Spindles, which secure the tool and its holder, are key in determining machine tool accuracy. In early machine tools, the spindles were simple bearing-- mounted shafts driven by a constant-speed electric motor, achieving different speeds through belts and gears. Operators changed spindle speed by shifting gears or moving belts to and from various pulleys.
As drive motors achieved higher torque and were designed to operate at variable speeds, belt and gear-driven systems began to wane in popularity, but both are still used. Stronger, longer-wearing, quieter belt and gear-- drive designs have been developed. Variable-speed direct drive, or integral-- motor spindles have replaced geared spindles for high-speed applications. At the same time, spindles with planetary gear systems, much like a car's automatic transmission, are now used to provide a wide torque output.
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