An indexable drill is a type of cutting tool that is able to penetrate through the workpieces in order to produce holes and contour the profiles of the holes at the same time, which maximize the use of a cutting tool during the machining works.
Similar to the standard drill bit, the indexable drill is mainly used for drilling holes on the workpiece by removing the materials as the tool penetrates through the surfaces of the work, with the similar design of the grooves on the tip of the tool that allow the chips to pass through without blockage and the coolant to be fed into.
While the indexable drill is also called the indexable insert drill, which means that in addition to the original tool body, there is still an insert that can be replaced between the insertion and removal of different pieces when it is necessary.
During the precision machining works, the drill bits play significant roles in producing holes on the workpieces depending on the required geometries, and whether the cuts are accurate and precise or not is the most important parameter that determines the make-or-break of the final products.
As the workpieces that are supposed to be cut have to be centered in place during the operation, the centering of the cutting tools is no exception. Therefore, the indexable drills are applied, as they are able to self-center when they are performing the cuts on the workpieces.
With the ability to produce holes and contour the profiles on the workpieces at the same time, and the self-centering characteristic, the versatility of the indexable drills cannot be emphasized more, which explains the reason why they are widely adopted over the standard drill bits.
An indexable drill consists of two main parts, and these two parts are attached to each other, including the tool body and the inserts.
● Tool body
The tool body is the part that holds the inserts when the tool performs the cuts. It is held by the tool holder on above, and can stay stationary during the replacement of the inserts, which avoid the requirement to adjust the position of the tool or the distance between the tool and the workpieces.
The inserts are the cutting tips on this type of tool. They are required to be replaced when they become dull or discarded. In addition, the only replacement of the tools reduces the time that is spent on changing the tools, and thus increases the efficiency of the works.
The invention of the indexable drill can be derived from the standard drill bit, which is formed by the tool body and the cutting tip. However, although the components of these two types of cutting tools are identical, there are still some variations between each of them, and these variations can be compared in the tool formation, the hole diameter, and the performance.
● Tool formation
As the above introduction has mentioned, the indexable drill consists of not only the tool body but also the inserts. The tool body is held by the tool holder, and the inserts are inserted and clamped by the former. The former and the latter of this type of tool can be separated, which means the inserts can be replaced when it is necessary.
Besides, on the indexable drill, there is the inner insert and the outer insert respectively. The inner insert is the part that drills the holes on the workpieces, and the outer one is in charge of enlarging or cutting the outside holes out of the inner holes.
In contrast, the cutting tip, which is the inserts on the indexable drill, of the standard drill bit cannot be separated from the tool body, as these two parts on the standard drill bit are attached to each other. In other words, when it is required to change the standard drill bit with different diameter or form, the entire tool, including the body and the tip, have to be replaced together.
● Hole diameter
When it comes to the hole diameter that the cutting tools can achieve, it is related to the diameter of the cutting parts of the tools. In general, the indexable drills are capable of attaining larger hole diameter than the standard drill bits.
Since the inserts of the former are interchangeable, and one drill contains both inner and outer inserts, which allows for producing larger holes accordingly. In contrast, the range of the larger hole diameters would be limited with the standard drill bits. While inversely, they perform better in drilling holes with smaller diameters.
One of the special features that make the indexable drills surpass the standard drill bits is that they own the split point. Since the former type of tool has the ability of self-centering, they can prevent the tools from deviating before they cut through the workpieces, which thus facilitate faster cutting speed and smoother surface finishes on the final products.
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