Spot drilling is a kind of chamfering technology. The larger the spot drill, the larger the chamfer would be.
The spot drill is designed for precisely spotting a hole for preventing the drill walking. In fact, the spot drill has the ability of guiding the drill tip to the right place when doing the secondary drilling. When applying this technology, the location of the center of the drill would be ensured.
Therefore, spot drills are produced quite rigid and extremely hard with stub length for the stability purpose. Moreover, their flute length is designed pretty short. Thus, it would be guaranteed that the spot drill can make marks on many kinds of metals as well, and surely preparing for the secondary drilling progress.
The spot drill is used to mark the point for drilling. Shortly to say, it is the first step to precision drilling.
In fact, precising drilling is difficult to do since the decisive factor can be various such as the hardness of the drill, the power of the machine tool, surface irregularities, and drill point geometry, or the kinds of workpieces made of different metals.
All the factors above might lead to the result of inaccurate hole drilling.
In addition, before doing precision drilling, using the spot drill can help to ensure the hole is accurately located.
Since the spot drill has marked the drilling point the first, when the drilling work operates, the chance of drill walking would be highly eliminated. Thus, the quality of the final products would be ensured and make the next progression goes smoothly.
However, if the carbide spotting drill is applied, then the step of spot drilling would not be necessary since the carbide spotting drill itself contains the function of spot drill.
Spot drilling is a kind of application of chamfer technology. To do spot drilling properly, there are some points to notice.
● Choose a Proper Spot Drill
Ideally, the center of the spot drill, or carbide spotting drill, should be the first contact point to the surface of the metals which are ready to be marked.
Moreover, the angle of the spot drill should be either equal to or a little bit larger than the drill you are going to use to do drilling progress later.
It is because that if the angle of spot drill is smaller, the first contact point of the drill in progression would not be the center.
Moreover, if the outer portion of the cutting surface contact the workpiece before the center, it would cause a shock loading which surely crash the drill. Then, the tool and workpiece would both be broken.
● Mark the Spot
Now, after checking the drill is chosen right, you can start the spot drilling.
When mark the spot, the spot drill just needs to dill the surface of the metal in a specific depth. Then, the whole progress would be done in the secondary drilling.
NC spot drill is one kind of the spot drills. They are a kind of high precision drills that designed specifically for creating an accurate hole location for a secondary drilling operation.
This kind of spot drill do not have body clearance. Moreover, they are not allowed to be designed to be larger than the depth of the point angle.
Briefly, this kind of spot drills are designed in the following angles:
● 142˚ NC Spot Drill
This kind of spot drill is used to preparing the accurate start point for the secondary drilling using of 135˚ or 140˚ angles.
● 90˚ and 120˚ NC Spot / Chamfer Drills
This kind of drills can be the spotting tool for 118˚, 120˚, 130˚ or 135˚ high speed steel drills. When tapping drill holes, they can also be used as chamfering tools.
Actually, not really.
For secondary drilling preparation, center drilling is another kind of techniques that would be used.
This kind of drilling technique is suitable for creating a hole suitable for a lathe center. The drill applying this technique has a two part tip that has a small pilot as well as the larger countersinking area of the bit.
In general, center drill is less expensive than the spot drill. However, it contains more disadvantages. For example, the small pilot tip, since they are dedicated, the whole drill will quit cutting. Then, it would in some level cause the reduction of productivity.
Moreover, the hole angle of a center drill is typically 60 degrees. However, we know that the spot drill angle should be either equal to or a little bit larger than the drill you are going to use to do drilling progress later.
Thus, when the situation comes with doing spot drilling with a 60 degrees angle, the following condition would be hard to fulfill. In addition, the purpose of spot drilling would not be occurred.
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