Deep Hole Drilling for Rifle Barrels

Deep Hole Drilling for Rifle Barrels

A machining process that began with the need to drill straighter, more precise gun barrels, deep hole drilling has revolutionized industries that require intricate and elongated holes in metal workpieces.deep hole drilling rifle drilling Deep hole drilling, which includes gun and BTA drilling methods, enables tight diameter control and hole straightness in CNC machining materials from aluminum to super-alloys. This article delves into the nuances of this advanced, highly accurate machining technique.

Rifle barrels require a bore with a length that is much longer than its diameter; for example, a standard rifle barrel has a length of about 20 inches (510 mm).deep hole drilling rifle drilling This makes it difficult to make a straight hole through the entire length of the barrel using a twist drill. A specialized tool called a gun drill was developed to meet the challenges of drilling such long, straight, and large-diameter holes. Gun drills feature a single cutting edge with straight flutes for chip removal, and they can achieve accuracy levels that are significantly higher than traditional twist-drills.

A major challenge with gun drilling is that the drill bits used for this application are extremely hard, and as a result, they have a short tool life and poor quality.deep hole drilling rifle drilling This is particularly true with hard, tough metals such as Inconel 718, which can easily crack and fracture if the drill bit is exposed to high temperatures. In order to address this, a team of researchers at Precihole Machine Tools has developed a new tool design for gun drills that uses a layer of polycrystalline cubic boron nitride (PCBN) on the tip and bearing pads of the tool to improve tool life and hole-quality, even in difficult-to-machine materials like Inconel 718.

The gun drill's PCBN coating increases its wear resistance and reduces the amount of heat it generates while cutting. This helps the drill to last longer, while retaining its excellent performance characteristics, such as precision and speed. The coating also eliminates the need for frequent tool changes, thereby improving productivity and lowering manufacturing costs.

Another benefit of the gun drill is its ability to cut through Inconel 718 with a significantly reduced level of burrs and other defects. As a result, the finished product is easier to clean, which helps ensure that it meets rigorous military and industry standards for cleanliness and corrosion resistance.

After the drilled hole is finished, it must be reamed and lapped to correct minor variations in bore straightness, as well as to establish the final bore diameter. A reamer is a long, smooth cutting tool that is typically the same diameter as the finished bore for consistency.

During reaming, the reamer may leave marks that could transfer to a fired bullet, so it is critical to use a high-quality tool with an accurate bore size. The markings left by the reamer can be difficult to remove, so barrel makers often rely on an optical pattern that is projected onto the inside of the barrel to identify and correct any deviations.

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