How to Choose the Suitable Carbide Twist Drills?
Learning how to choose the best carbide twist drill is not as easy. Especially as you choose from the simple HSS twist drill to the vast array of solid carbide drills, indexable insert drill, and multi-function carbide drills, the choices can be overwhelming.
Here are some factors to consider when choosing a carbide twist drill
1. Application.
If you are only drilling a few holes in mild steel and the time requirements are insignificant, the HSS twist drill would likely work just fine. However, with tougher tool steels, such as H-13, S-7, A-6, D-2, or 420SS, the carbide drills will be better.
2. Size of drilling hole.
For the size of drilling holes under .5 inch. The solid carbide twist drills will be required. Solid carbide is available in an almost unlimited size range.
3. Budget.
The drill bits can be costly and must be justifiable to make sense. There is also a tendency to use more than is necessary when the tool crib is full of helpful, shiny new cutting tools. From Heygo Tools, you will get many different types of drill bits with a cost-effective price for your various budgets.
4. Surface Treatment
Surface finish requirements play an essential role in the selection process of the twist drill. Generally, the solid carbide drills leave an excellent finish, but for larger holes, the indexable inserts drills can also do an excellent job.
5. Coatings for carbide twist drills.
According to the application situation, the coatings suitable for cemented carbide twist drills can be roughly divided into the following five types:
Uncoating (Bright):
Uncoated twist drill bits are the cheapest and are usually used for soft materials such as aluminum alloys and mild steel.
Tin Coating:
Titanium(TIN) is the most common coating material and is not suitable for processing materials with high hardness or processing temperature.
TiCN coating:
TiCN is developed from TiN and has a higher heat resistance and wear resistance. Its color is usually purple or blue.
TiAlN coating:
The TiAlN coating is more resistant to high temperatures than all the above coatings so that it can be used in high-temperature environments, such as high-temperature alloys. It is also suitable for the processing of steel and stainless steel. Still, due to the elemental aluminum, chemical reactions occur when processing aluminum, so it cannot be used for aluminum-containing materials.
5. Geometric Features
The geometric characteristics of the drill bit can be divided into the following three parts:
The length of the twist drill bit.
The length and diameter are relatively small, and the rigidity is excellent. The drill bit has a suitable chip evacuation length, and the chip evacuation length is as short as possible, which can increase the rigidity during the processing and thereby prolong the service life of the tool. If the flute is not long enough, the drill bit may be damaged.
Drill point angle
A point angle of 118 degrees is probably the most common angle in processing and is usually used for soft metals such as mild steel and aluminum. Often, this design does not have an automatic centering function, which means that the centering hole must be machined first. The 135-degree angle usually has a self-centering function, because there is no need to process the centering hole, so it is no longer necessary to drill the centering hole separately, thereby saving a lot of time.
Helix angle
For most materials, a helix angle of 30 is the right choice. However, for environments that require better chip removal and improved cutting edge strength, a smaller helix angle is better. For materials that are difficult to process, such as stainless steel, a larger helix angle can be selected to transmit torque.
