A welded carbide drill bit, which is known for its high joint strength between the drill tip and the cutter body, can produce a hole with a relatively good surface roughness, a small aperture tolerance, and a high positional accuracy.
When tightening the locking screw, the crown drill can reach the same feed rate as the welding bit
Many factories mistakenly believe that drilling must be done at low feed rates and low speeds. This has been true in the past, but the situation with today's carbide drills is different. In fact, users who choose the right drill can dramatically increase productivity and reduce overall cost per hole.
For the end user there are four basic forms of drill bits with carbide cutting edges: solid carbide, indexable inserts, welded carbide tips and interchangeable carbide tips. Each has its advantages in a particular application.
The first solid carbide drill bit was used in modern machining centers. It is made of fine-grained hard alloy and has a TiAlN coating for improved tool life. These self-centering drills provide excellent chip control and chip removal in most workpiece materials due to their specially designed cutting edges. . The self-centering geometry and good precision of the solid carbide drill ensure high quality holes without any further processing.
Indexable insert drills cover a wide range of diameters when drilling depths from 2XD to 5XD. They can be used in both rotary and lathe applications. For most workpiece materials, these drills use a self-centering geometry to reduce cutting forces and good chip control.
The holes drilled by the welding bit have a relatively high surface finish, high dimensional accuracy and good positional accuracy without further finishing. Thanks to the cooling through holes, the welding drill bit can be used in machining centers, CNC lathes or other machines with sufficient stability and speed.
The last type of drill bit combines a steel body with a replaceable solid carbide tip called a crown. This type of drill bit achieves higher productivity at a lower processing cost while providing the same precision as a welded drill bit. This new generation of drill bits with a carbide crown provides precise dimensional increments and a self-centering geometry that guarantees high dimensional accuracy.
Careful consideration of tolerances and machine stability
The factory should select the drill bit based on the specific tolerances of the machining. Usually the tolerance of the small diameter holes is tighter. The drill manufacturer then classifies the drill bit by specifying the nominal bore diameter and the upper tolerance.
In all drill forms, the overall carbide drill has the tightest tolerance. This makes them the best choice for drilling holes with tight tolerances. The factory can drill from a solid carbide drill with a diameter of 10 mm to a tolerance of 0 to +0.03 mm.
On the other hand, a drill bit or a Seco drill with a replaceable carbide crown has a tolerance of 0 to +0.07 mm. These drill bits are often a good choice for drilling production.
The indexable insert bit is an industrial heavy duty drill bit. Although their upfront cost is usually lower than other drill bits, the drill also has the largest tolerances from 0 to +0.3 mm depending on the diameter/hole depth ratio tolerance. This means that the end user can use the indexable insert bit when the tolerance of the hole is large, otherwise they must prepare the hole for finishing with a file.
Together with the tolerances of the holes, the plant needs to consider the stability of the machine during the selection process. Because stability is the guarantee of tool life and drilling accuracy. The factory should verify the status of the machine's spindles, fixtures and accessories.
They should also consider the inherent stability of the drill bit. For example, a solid carbide drill provides optimum rigidity, which allows it to achieve high precision.
On the other hand, the indexable insert bit is easily deflected. These drills are equipped with two blades - one inside the center blade and the blade extending outward from the inside blade to the edge - initially with only one blade participating in the cutting. This creates an unstable situation that causes the bit body to deflect. Moreover, the bit length of the bit is larger. Therefore, when using the indexable insert drills of 4XD and above, the factory should consider reducing the feed rate during the first millimeter of machining and then increasing to the normal feed.
The welding bit and the replaceable crown bit are designed to be two symmetrical cutting edges that form a self-centering geometry. This highly stable cutting design allows the drill bit to enter the workpiece at full speed feed. The only exception is when the drill bit and the machined surface are not perpendicular, it is recommended to reduce the feed by 30% to 50% when cutting in and out. The steel drill body allows slight deflection to occur, allowing it to be successfully applied to lathes. Rigid solid carbide drills can be easily broken, especially when the workpiece is not centered.
Don't ignore the chips
Many factories have problems with chip removal. In fact, the difference in chip evacuation is the most common problem in drilling, especially when machining low carbon steel. And no matter what kind of drill is used.
Factories often use external cooling to solve this problem, but this only works for hole depths less than 1XD and reduces cutting parameters. Otherwise, they must use a suitable coolant with a flow and pressure that matches the pore size. For machines that do not have spindle center cooling, the plant should use a coolant external transfer unit.
Keep in mind that the deeper the hole, the more difficult it is to remove chips and the need for greater cooling pressure. Always check the manufacturer's recommended minimum coolant flow level. At lower flow rates, it may be necessary to reduce the feed rate.
Check life cycle costs
Productivity or cost per hole is the biggest trend affecting today's drilling. This means that bit manufacturers must find ways to combine certain processes and develop drill bits that can accommodate high feed rates and high speed machining.
The latest drills with interchangeable solid carbide tips provide superior economy. Instead of replacing the entire bit body, the end user only purchases a carbide tip that is equivalent to re-grinding a welded bit or a solid carbide bit. These crowns are easy and precise to replace, and the factory can use multiple crowns on one drill body to drill several different sizes of air.
This modular drilling system reduces the inventory cost of drill bits from 12mm to 20mm in diameter. In addition, it eliminates the cost of backing up the drill bit when re-grinding a welded drill bit or a solid carbide bit.
The factory should also take into account the total tool life when reviewing the cost per hole. Usually, for a factory, a solid carbide drill can be reground 7 to 10 times, while a welded drill can only be reground 3 to 4 times. On the other hand, the steel body of the crown type drill can exchange at least 20 to 30 crowns when machining steel.
There is also a productivity issue here. Welded drill bits or solid carbide drills must be reground; therefore, the factory tends to reduce speed to avoid sticking. However, the drill bit of the replaceable cutter head does not have to be reground, so the factory can use the feed rate and speed during processing without worrying about the stickiness of the cemented carbide material.
This new crown-type drill has a more consistent tool life than a welded or solid carbide drill. In many cases, the reground bit does not reach the performance of the new bit. This is because it is difficult to reshape the cutting edge shape and the edge grinding to be exactly the same as the new one. Improper edge grinding can make the drill bit more susceptible to sticking, requiring more torque or power to process, or generating more heat, thus reducing tool life.
When tightening the locking screw, the crown drill can reach the same feed rate as the welding bit
Many factories mistakenly believe that drilling must be done at low feed rates and low speeds. This has been true in the past, but the situation with today's carbide drills is different. In fact, users who choose the right drill can dramatically increase productivity and reduce overall cost per hole.
For the end user there are four basic forms of drill bits with carbide cutting edges: solid carbide, indexable inserts, welded carbide tips and interchangeable carbide tips. Each has its advantages in a particular application.
The first solid carbide drill bit was used in modern machining centers. It is made of fine-grained hard alloy and has a TiAlN coating for improved tool life. These self-centering drills provide excellent chip control and chip removal in most workpiece materials due to their specially designed cutting edges. . The self-centering geometry and good precision of the solid carbide drill ensure high quality holes without any further processing.
Indexable insert drills cover a wide range of diameters when drilling depths from 2XD to 5XD. They can be used in both rotary and lathe applications. For most workpiece materials, these drills use a self-centering geometry to reduce cutting forces and good chip control.
The holes drilled by the welding bit have a relatively high surface finish, high dimensional accuracy and good positional accuracy without further finishing. Thanks to the cooling through holes, the welding drill bit can be used in machining centers, CNC lathes or other machines with sufficient stability and speed.
The last type of drill bit combines a steel body with a replaceable solid carbide tip called a crown. This type of drill bit achieves higher productivity at a lower processing cost while providing the same precision as a welded drill bit. This new generation of drill bits with a carbide crown provides precise dimensional increments and a self-centering geometry that guarantees high dimensional accuracy.
Careful consideration of tolerances and machine stability
The factory should select the drill bit based on the specific tolerances of the machining. Usually the tolerance of the small diameter holes is tighter. The drill manufacturer then classifies the drill bit by specifying the nominal bore diameter and the upper tolerance.
In all drill forms, the overall carbide drill has the tightest tolerance. This makes them the best choice for drilling holes with tight tolerances. The factory can drill from a solid carbide drill with a diameter of 10 mm to a tolerance of 0 to +0.03 mm.
On the other hand, a drill bit or a Seco drill with a replaceable carbide crown has a tolerance of 0 to +0.07 mm. These drill bits are often a good choice for drilling production.
The indexable insert bit is an industrial heavy duty drill bit. Although their upfront cost is usually lower than other drill bits, the drill also has the largest tolerances from 0 to +0.3 mm depending on the diameter/hole depth ratio tolerance. This means that the end user can use the indexable insert bit when the tolerance of the hole is large, otherwise they must prepare the hole for finishing with a file.
Together with the tolerances of the holes, the plant needs to consider the stability of the machine during the selection process. Because stability is the guarantee of tool life and drilling accuracy. The factory should verify the status of the machine's spindles, fixtures and accessories.
They should also consider the inherent stability of the drill bit. For example, a solid carbide drill provides optimum rigidity, which allows it to achieve high precision.
On the other hand, the indexable insert bit is easily deflected. These drills are equipped with two blades - one inside the center blade and the blade extending outward from the inside blade to the edge - initially with only one blade participating in the cutting. This creates an unstable situation that causes the bit body to deflect. Moreover, the bit length of the bit is larger. Therefore, when using the indexable insert drills of 4XD and above, the factory should consider reducing the feed rate during the first millimeter of machining and then increasing to the normal feed.
The welding bit and the replaceable crown bit are designed to be two symmetrical cutting edges that form a self-centering geometry. This highly stable cutting design allows the drill bit to enter the workpiece at full speed feed. The only exception is when the drill bit and the machined surface are not perpendicular, it is recommended to reduce the feed by 30% to 50% when cutting in and out. The steel drill body allows slight deflection to occur, allowing it to be successfully applied to lathes. Rigid solid carbide drills can be easily broken, especially when the workpiece is not centered.
Don't ignore the chips
Many factories have problems with chip removal. In fact, the difference in chip evacuation is the most common problem in drilling, especially when machining low carbon steel. And no matter what kind of drill is used.
Factories often use external cooling to solve this problem, but this only works for hole depths less than 1XD and reduces cutting parameters. Otherwise, they must use a suitable coolant with a flow and pressure that matches the pore size. For machines that do not have spindle center cooling, the plant should use a coolant external transfer unit.
Keep in mind that the deeper the hole, the more difficult it is to remove chips and the need for greater cooling pressure. Always check the manufacturer's recommended minimum coolant flow level. At lower flow rates, it may be necessary to reduce the feed rate.
Check life cycle costs
Productivity or cost per hole is the biggest trend affecting today's drilling. This means that bit manufacturers must find ways to combine certain processes and develop drill bits that can accommodate high feed rates and high speed machining.
The latest drills with interchangeable solid carbide tips provide superior economy. Instead of replacing the entire bit body, the end user only purchases a carbide tip that is equivalent to re-grinding a welded bit or a solid carbide bit. These crowns are easy and precise to replace, and the factory can use multiple crowns on one drill body to drill several different sizes of air.
This modular drilling system reduces the inventory cost of drill bits from 12mm to 20mm in diameter. In addition, it eliminates the cost of backing up the drill bit when re-grinding a welded drill bit or a solid carbide bit.
The factory should also take into account the total tool life when reviewing the cost per hole. Usually, for a factory, a solid carbide drill can be reground 7 to 10 times, while a welded drill can only be reground 3 to 4 times. On the other hand, the steel body of the crown type drill can exchange at least 20 to 30 crowns when machining steel.
There is also a productivity issue here. Welded drill bits or solid carbide drills must be reground; therefore, the factory tends to reduce speed to avoid sticking. However, the drill bit of the replaceable cutter head does not have to be reground, so the factory can use the feed rate and speed during processing without worrying about the stickiness of the cemented carbide material.
This new crown-type drill has a more consistent tool life than a welded or solid carbide drill. In many cases, the reground bit does not reach the performance of the new bit. This is because it is difficult to reshape the cutting edge shape and the edge grinding to be exactly the same as the new one. Improper edge grinding can make the drill bit more susceptible to sticking, requiring more torque or power to process, or generating more heat, thus reducing tool life.
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