What Is a Boring Bar?
A boring bar is a specialized tool used in machining to perform boring operations, which involve enlarging a pre-drilled hole to precise dimensions with high accuracy and smoothness. It typically comprises a single-blade tool and a dimensional adjustment screw, offering enhanced precision and roundness compared to other hole-finishing methods.
Uses of Boring Bars
Boring bars are essential for creating precision holes, especially in industrial products like engine and transmission joints or gear holes. They are favored for machining holes with tight tolerances (H7 and H6), ensuring superior surface roughness and roundness compared to end mills.
Principle of Boring Bars
The tool features an insert-replaceable blade and an adjustment screw for dimensional fine-tuning. Proper adjustment is crucial to match the pre-drilled hole size before machining, with careful programming needed to avoid surface imperfections during the machining process.
Types of Boring Bars
Boring bars are categorized based on the material and application:
1. High-Speed Boring Bars
Best suited for roughing operations and finishing holes larger than 15 mm in diameter with general tolerances.
2. Tungsten Carbide Boring Bars
These are harder than high-speed steel (HSS) and are preferred for precision machining of holes 15 mm in diameter or smaller. They offer long-term cost benefits due to their durability and time efficiency, despite higher initial costs and brittleness.
Other Information on Boring Bars
Adjusting Boring Bars
Adjustment involves turning the built-in screw to alter the tool’s dimension, with digital and analog scale options available. Despite the convenience of digital scales, both types require careful calibration to ensure accuracy.