Understanding the different types of boring tools is crucial for anyone undertaking car engine boring at home. Using the incorrect tool can lead to unsatisfactory results and potential damage. This guide explains the three main types of boring bar profiles – positive lead, negative lead, and zero lead – and their specific applications, ensuring you select the right tool for your home car engine boring needs.
Boring tools are differentiated by the cutting edge at their tip. Examining the tool tip from above reveals three distinct configurations. The cutting edge can slope away from the headstock (positive lead), slope towards the headstock (negative lead), or be almost perpendicular to the lathe axis (zero lead).
Positive Lead Boring Tools: Ideal for Facing Operations
Positive lead boring tools are specifically designed for facing, which involves cutting from the center of a hole outwards. This makes them perfect for creating flat-bottomed blind holes or shoulders, often required in bearing housings and similar components within car engines. The design of a positive lead tool ensures efficient material removal when facing surfaces inside a bore.
However, it’s crucial to avoid using positive lead tools for cutting down the length of a bore. Boring tools, due to their function, are typically slender and thus somewhat flexible. When used to cut along the bore’s side, a positive lead tool tends to dig in. This digging action causes the tool to bend away from the bore axis, resulting in a bore that is narrower at the entrance and wider internally. This can lead to inaccuracies and a poor finish in cylinder boring for car engines.
Negative Lead Boring Tools: Best for Bore Sides
For cutting along the sides of a bore, negative lead tools are the optimal choice. These tools are designed to pass completely through the bore as the front of the tool extends beyond the cutting tip. The angled cutting edge of a negative lead tool applies force that flexes the tool towards the bore’s axis. This action initially produces a bore that is narrower inside than at the entrance. However, repeating the final cut several times at the same setting compensates for this “spring,” leading to a more accurate and consistently sized bore, essential for car engine cylinder work.
Zero Lead Boring Tools: A Versatile Compromise
Zero lead tools represent a compromise, offering versatility for different boring tasks. While not the absolute best for either facing or side boring, they allow you to bore the side of a blind hole or bore up to a shoulder. Often set at 91 degrees to the axis rather than a perfect 90 degrees, these tools provide a practical solution when you need to perform both facing and side boring operations without changing tools, which can be useful in certain home car engine boring scenarios.
Visual Example of Positive Lead Tool
To further illustrate, positive lead tools exhibit a distinct cutting edge profile suited for specific tasks.
In conclusion, selecting the correct boring tool type – positive, negative, or zero lead – is vital for achieving accurate and professional results when boring car engines at home. Understanding the strengths and limitations of each type ensures that you choose the most appropriate tool for each specific boring operation, whether it’s facing, side boring, or working in blind holes.
