A spotting hole drill bit can be named a hole starting drill bit. Both are similar tools. It has a tight tolerance point geometry with a very short flute length. To start holes and precisely find them, spotting drill bits are utilized. When drilling begins, they make a small hole that helps stop drill bits from walking or moving.
The role of the spot drill is also changing, and it is no longer just used for drilling pilot holes. Additionally, it is possible to drill and mill cutters in one piece in addition to milling edges. The angles, which can be 60, 90, or 120 degrees.
Although spot drilling is not recommended in hardened steels.
Where to Use Spotting Hole Drill Bits?
A very precise hole can be challenging to drill. Drill point shape, surface imperfections, and material behavior all contribute to incorrect holes. If utilized properly, a spot drill will help to assure a more precise final result by removing the possibility of drill walking.
It can be employed for a variety of operations. Those are;
- Drilling of spotting holes
- Bored surfaces,
- Engraved surfaces,
- Chamfered surfaces,
- Deburred edges, etc.
Making a tiny pivot with a spotting drill will help you find the drill’s center when you start a plunge. Some machinists use these tools to chamfer the top of drilled holes, which is a different function for them. When inserted, screw heads sit flush with the component thanks to the chamfer.
What Is the Color and Material of the Spotting Hole Drill Bit?
There have a few types of spotting drill bits based on the material. Those are;
- Carbide Spotting drill bit
- High-speed steel spotting drill bit
- Cobalt spotting drill bit
- Carbide Spotting Drill Bit
Solid carbide spotting drills offer good wear resistance when drilling into the toughest materials because they are harder than cobalt steel and high-speed steel spotting drills. A wide range of carbide spotting hole drill bits are in the market based on the bit size and the angle of the.
Coated and uncoated drill bits are in the market. Uncoated carbide spotting drill bits brightly appears. “TiAlN” and “TiN” coatings are available.
- High-Speed Steel Spotting Drill Bit
High-speed steel spotting drills are the most popular option. Drills made of high-speed steel are often less brittle than those made of cobalt or carbide.
Coated and uncoated drill bits are in the market. Uncoated carbide spotting drill bits brightly appears. “TiN” coating type is available.
- Cobalt Spotting Drill Bit
Cobalt steel spotting drills are excellent for drilling into tough materials and offer greater wear resistance at higher speeds than high-speed steel spotting drills. Uncoated cobalt spotting drill bits brightly appears.
What Is the Cutting Angle of the Spotting Hole Drill Bit?
The typical tip angles for secondary drill bits are 118°, 120°, or 135°, with bigger tip angles used for drills with higher strength needs. Some people center a hole for a secondary drill with a 135° tip angle using a 145° spot drill.
It is crucial to use a 145° spot drill when machining certain of the harder workpiece materials, such as stainless steel or Inconel alloys, because the second drill is more vulnerable to damage.
However, the majority of individuals simply utilize the spot drill they have access to in their workshop, like a 90° spot drill, for any machining.
The majority of tool makers concur that; a spot drill’s tip angle should be either greater than or equal to that of a secondary drill.
In order to prevent excessive cutting pressure on the drill’s cutting edge, which can result in early tool failure and poor hole quality, the secondary drill should make contact with the spotting hole using its drill tip rather than its cutting edge.
By directing the drill’s tip toward the center, a larger angle drill will help the drill locate the proper spot. A carbide drill could chip if the outer diameter came into contact with the work piece first. As a result, the workpiece would be harmed, and the tool would be flawed.
If the drill’s two flutes differed slightly from one another, one might make contact with the other before the other. This can result in an incorrect hole and potentially defeat the goal of spot drilling altogether.
Spotting Hole Drill Bit Size Chart
| Diameter of spot drill bit/(Inch) | Length deviation due to the flat/(Inch) |
| 3/8 | 0.026 |
| 1/2 | 0.035 |
| 3/4 | 0.045 |
| 1 | 0.060 |
The size of the spot hole drill bit is widely varied. It depends on the material type also. Here are a few examples to prove it.
| Material | Tip Angle | Drill Bit Size/(Inch) | Flute length/(Inch) | Overall Length/(Inch) |
| Carbide | 90o | 0.0050 | 0.0250 | 1-1/2 |
| 82o | 0.0050 | 1 | 2-1/2 | |
| 82o | 0.0050 | 1 | 3 | |
| 82o | 0.0050 | 1-1/4 | 3 | |
| High-Speed Steel & Cobalt | 82o | 0.0050 | 1-3/8 | 3-3/4 |
| 820 | 0.0050 | 1-3/8 | 6 | |
| 82o | 0.0050 | 1-3/8 | 8 | |
| Cobalt | 900 | 0.0050 | 0.984 | 4-1/64 |
| 90o | 0.0050 | 1-3/8 | 1-3/4 | |
| 90o | 0.0050 | 1-3/8 | 6 | |
| 90o | 0.0050 | 1-3/8 | 8 |
Above is the variation in other characteristics related to a common drill bit size. There are a wide range of spotting hole drill bits on the market.
What is the Difference Between Spotting Hole Drill Bit and Center Drill Bit?
Both of the center drill bit and spotting hole drill bit are used for pilot hole drilling.
But the spotting drill bit has a 120-degree angle, and the center drill bit has a tapered 60-degree angle with 120 tip conical angle. When a center drill is used to drill a pilot hole, there are two different sizes of holes in the material.
The regular drill bit has a 118-degree angle. When it uses on the pilot hole, which was drilled using a center drill bit there is a chance to deflect or slipper the drill bit a little bit due to less contact with the surface. Hence the accuracy can be reduced in a certain extent.
But the spot drill bit has a 120-degree cutting angle, and it can fit a 118-degree angle drill bit perfectly. So spot drill bit is very good for pilot hole drilling with high accuracy for the secondary drilling.
