Cut to The Bit

Poorly Performing Bits Cost Time And Money. Check Out Carbide Tips for More Efficient Drilling, without Breaking the Bank

By Fulvio Camaratto, Hammer Carbide Product Manager, Bosch Accessories, Ed Pchola, Group Product Manager, Bosch Accessories -- Industrial Distribution, 4/1/2006

When it comes to drilling concrete, time is money. The productivity of a carbide rotary hammer drill bit can mean the difference between profit and loss for a customer. While at a glance, hammer carbide may not seem complicated, a closer look reveals differences in bit anatomy and manufacturing that directly relate to performance. As you consider your next hammer carbide line, or simply recommend a bit to a customer, keep the following in mind.

The carbide rotary hammer drill bit offers the best balance between efficiency and price. Though diamond bits may be more efficient, few customers can afford to pay the premium. As a result, carbide remains the primary bit of choice, and is frequently purchased in large quantities by contractors and other customers.

The carbide portion of a rotary hammer bit is called the cutter, or small piece (or pieces) of carbide braised to the bit's head to create the tip. To maximize overall efficiency, manufacturers configure cutters in three ways:

• A "standard cutter" utilizes a single piece of carbide spanning across the center;
• A "multi cutter" utilizes a standard cutter and two smaller secondary cutters almost perpendicular to the first;
• The "multi-cutter reinforced" includes a multi-cutter with larger secondary cutters.

As a general rule, the more cutters on the tip, especially for larger bits, the more efficient it will be.

When suggesting any bit, make sure to understand its head and cutter geometry. This design feature helps ensure the bit does not easily bind when it strikes rebar. It also helps the bit drill concentric holes and avoid walking along the concrete during the initial drilling process. Clean holes are important for concrete anchors to grip the inner wall. And finally, a well-designed bit geometry will allow it to last longer.

A broken tip should not be a frequent occurrence. Unfortunately, not all bits are manufactured the same, and customers frequently are reminded of this, especially after purchasing low cost bits. To avoid customer disappointment, take into consideration how vendors braise or weld cutters to the head. Some companies braise precisely molded pieces of carbide within the tip, eliminating unneeded surface area and providing maximum support from all sides, making it less likely to break. Other manufacturers braise a single piece of carbide ground to sit on top or cap the bit. This process requires more braising and results in less carbide support. Vulnerable from all sides, it is more likely to break.

In reality, a lot of factors can play into the failure of a bit. But one absolute is overheating the bit with excess debris. Stagnant dust in a hole with a spinning carbide bit creates friction, resulting in heat. If the dust is not removed, excessive heat can damage the integrity of the bit and slow its progress. To avoid any potential hazard, manufacturers consistently refine hammer bit debris removal systems, which consist of features called shoulders and flutes.

A bit's shoulders are pathways or guides for debris to travel from the cutters to the flutes. Research proves that larger shoulders offer the most efficient dust removal and better overall bit performance. In short, the faster the dust can be removed, the faster and more productive the bit.

Flutes, the twisting channels that swirl up the side of the bit, are the most important part of the debris removal system. Responsible for transporting debris from the hole, they work like a conveyor belt. While most bits have only two flutes, some have four steep flutes. Just like traffic on a highway, the more channels for dust to travel within and the shorter the distance, the quicker the material can exit the hole. As a result, these bits stay cooler, last longer and perform better.

Also, bits come with one of three shank configurations, SDS-plus, Spline, or SDS-max, which directly correspond to three types of bit-holders found within hammers. Both the shanks and bit holders create a system designed to hold the bits in place for the best possible energy transfer and overall hammer performance. Of the three, the two SDS systems are the most commonly used because of their wide range of sizes, bit-holding abilities and power transfer.

A distributor's line of hammer carbide drill bits normally includes three types—all of which cover the array of hole dim-ensions professional customers demand—including solid, core and thru-hole.

Solid bits are the most common carbide bit in the U.S. Though they range from 5/32 to 1½ in. in diameter, more than 85 percent of the holes drilled in concrete are ¾ in. diameter or smaller to accommodate standard concrete anchors. Solid bits are available in SDS-plus, Spline and SDS-max with all three carbide configurations referenced above. The key to selecting solid bits is aggressive fluting and precisely molded extra hard cutters for speed and long life.

Core bits look different than solid bits, but include all the same basic features. They range from 1 3/8 to 6 in. in diameter, and are available in all three shank types. Core bits extend solid bits beyond their largest capacities, evident in the fact that a solid bit serves as a pilot bit for the accessory. To achieve large diameter holes, core bits drill a donut shape into the concrete, leaving the core to be chipped out by the user. This two-step process is more time consuming than the third alternative, but it is more economical when it comes to the price of the bit.

Core bits also offer a unique challenge for both customers and distributors. Some manufacturers offer them in a component system design with interchangeable parts—cup with cutters, pilot bit and shank. In principle, this concept offers a unique selling proposition for customers. If a part has problems, replace the part instead of the entire bit. But in reality, after extended bit use, the two main pieces—the cutter and shank—usually become inseparable, as if welded together. In the end, customers still have to replace the entire bit.

Thru-hole bits are the newest to the market, ranging from 1¾ to 3 1/8-in. in diameter. Though not as large as core bits, they still require a Spline or SDS-max hammer. Unlike core bits, though, thru-hole bits offer the ability to continuously drill through concrete without the need to stop and chisel out the left-over core.

Thru-hole bits have an aggressive cutter design that grinds through material efficiently, while wide flutes and shoulders remove large and small debris with relative ease.

The market demands a broad range of prices for each type of bit, a benefit that also relates to high profit margins for distribution. The smallest solid bit retails for approximately $10 a five pack, while the largest retails for more than $100 per bit. Core bits and thru-hole bits range from $100 to more than $350 a piece, respectively. Guiding customers, especially when they can purchase up to 10,000 bits a year, is key.

Avoid disappointing customers by carrying quality carbide rotary hammer bits and helping customers choose the best selection for their time and money.

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