Drilling is an important part of PCB contour processing technology, and the selection of drill bit is particularly critical. The welded carbide bit, known for its high connection strength between drill tip and cutter body, can process holes with good surface roughness, small aperture tolerance and high position accuracy. When the locking screw is tightened, the crown drill can reach as high a feed as the welding bit.

Many people mistakenly believe that drilling must be done at low feed rates and low speeds. This used to be true, but today’s carbide bits are a different story. In fact, selecting the right bit can significantly increase productivity and reduce cost per hole across the board.

There are four basic types of drill bits with carbide cutting edges available to the end user: solid carbide, indexable inserts, welded carbide drill tips, and exchangeable carbide drill tips. Each has its advantages in a particular application.

The first solid carbide bits are used in modern machining centers. Manufactured from fine grained carbide and coated with TIAlN for tool life, these self-centering bits provide excellent chip control and removal in most workpiece materials due to their specially designed cutting edges. The self-centering geometry and precision of the integral carbide bits ensure that high-quality holes are achieved without any further machining.

Indexable blade bits cover a wide range of diameters at depths from 2XD to 5XD. They can be used in both rotary applications and lathes. These bits use a self-centering geometric Angle for most workpiece materials to reduce cutting force and provide good chip control.

The welded drill bit machined the holes with quite high surface finish, high dimensional accuracy and good position accuracy without further finishing. With cooling through holes, welded bit tips can be used in machining centers, CNC lathes, or other machine tools with sufficient stability and rotational speed.

The final bit form combines a steel cutter body with a removable solid carbide point called a crown. The drill provides the same precision as the welded bit while achieving higher productivity at a lower machining cost. This next generation bit with carbide crown provides precise dimensional increments and a self-centering geometric Angle that ensures high dimensional precision.

Carefully consider tolerances and machine tool stability

The factory should select the bit according to the specific tolerances on the machining. Small diameter holes usually have tighter tolerances. Thus, bit manufacturers classify bits by specifying nominal aperture and upper tolerances. Of all the drill forms, the solid carbide bit has the tightest tolerances. This makes them the best choice for drilling holes with extremely tight tolerances. The factory can drill with a 10mm diameter solid carbide bit with a tolerance from 0 to +0.03mm.

On the one hand, welded bits or high bits with a replaceable carbide crown can be drilled to a tolerance from 0 to +0.07mm. These bits are often a good choice for drilling production processes.Indexable blade bit is the heavy work bit in industry. While their upfront cost is typically lower than other bits, they also have the greatest tolerances, ranging from 0 to +0.3mm depending on the diameter-to-hole depth ratio. This means that the end user can use a indexable blade bit when the tolerance of the hole is high, otherwise they must be prepared to finish the hole with a boring cutter. Along with hole tolerances, the factory needs to consider the stability of the machine tool in the selection process. Because stability to ensure tool life and drilling accuracy. The factory shall verify the status of machine spindles, fixtures and accessories. They should also consider the inherent stability of the bit. For example, monolithic carbide bits provide optimal rigidity, which allows for high accuracy.

On the other hand, indexable blade bits tend to deflect. These bits are equipped with two blades — an inner blade in the center and a blade extending outward from the inner blade to the edge — and initially only one blade takes part in the cutting. This creates an unstable condition that causes the bit body to deflect. And the greater the bit moonlength deviation. Therefore, when using 4XD and more indexable blade bits, the plant should consider reducing the feed for the first mm and then increasing the feed to normal. The welded bit and the convertible crown bit are designed as two symmetrical cutting edges that form a self-centering geometric Angle. This stable cutting design allows the bit to enter the workpiece at full speed. The only exception is when the bit is not perpendicular to the surface being machined. It is recommended to reduce feed by 30% to 50% during cut and cut.

The steel bit body allows for slight deflection, enabling it to be used successfully on lathes. The solid carbide bit with good rigidity may be easily broken, especially when the workpiece is not centered properly. Don’t ignore chips many factories have problems with chip removal. In fact, poor chip removal is the most common problem in drilling, especially when machining mild steel. And it doesn’t matter what drill bit you use. Factories often use external cooling to solve this problem, but only for hole depths less than 1XD and with reduced cutting parameters. Otherwise, they must use the right coolant to match the flow and pressure of the aperture. For machine tools that do not have spindle center cooling, the factory should use a coolant out to in device. Remember, the deeper the hole, the more difficult it is to remove chips and the more cooling pressure is required. Always check the manufacturer’s recommended minimum coolant flow level. At lower flow rates, reduced feed may be necessary. Examining life cycle cost productivity or cost per hole is one of the biggest trends affecting drilling today. This means that bit manufacturers must find ways to combine certain processes and develop bits that can accommodate high feed rates and high-speed machining.

The latest bits with interchangeable solid carbide tips offer superior economy. Instead of replacing the entire bit body, the end user buys only a carbide head that costs the same as regrinding a welded or solid carbide bit. These crowns are easily replaceable and precise, allowing the factory to use multiple crowns on a single bit body to drill several different sizes of holes. This modular drilling system reduces inventory costs for bits with diameters from 12mm to 20mm.

In addition, it eliminates the cost of having a backup bit when a welded bit or solid carbide bit is reground. The factory should also take into account total tool life when reviewing cost per hole. Typically, a single carbide bit can be reground 7 to 10 times in a factory, while a welded bit can be reground 3 to 4 times. Crown drill bits, on the other hand, have a steel cutter body that can replace at least 20 to 30 crowns while machining the steel.

There is also the question of productivity. Welded or solid carbide bits must be reground; Therefore, factories tend to reduce speed to avoid sticky chips. However, the replaceable bit does not need to be reground, so the factory can process with sufficient feed and speed without worrying about cemented carbide chip.