How to Choose Point Drills vs. Center Drill Bits

How to Choose Point Drills vs. Center Drill Bits
How to Choose Point Drills vs. Center Drill Bits

Before drilling a hole, or when drilling a centering hole on a lathe. Spot drills and center drills may have similar features, but they are used for two different purposes.

What is a Center Drill Bit?

The geometry of a center drill is slightly different from that of a spot drill bit; they are shorter, have a tapered end, and are smaller in diameter. The main purpose is to create an accurate center point on the workpiece and create clearance for the tip of the lathe center. Center drill bits can also be used as countersinks to make countersunk screws flush with the surface.

The drill bit of a spot drill is relatively long and thicker than that of a center drill. And there is a center drill head tip to facilitate accurate positioning and drilling.

Center drills are mainly used to drill a hole in the center of a workpiece. This hole will serve as a guide or support for the center of rotation or center, and in some cases, it is the starting point for drilling larger diameter holes.

There are two common types of center drills, type A (DIN 333-A) with a 60-degree chamfer and type B (DIN 333-B) with two chamfers, the first 60 degrees and the second 120 degrees. Center drills are usually available in Metric or BS (British Standard) sizes.

How to Choose Point Drills vs. Center Drill Bits

Why Use a Center Drill?

Center drills (which can be made from high-speed steel or carbide) are used to make preliminary or pilot holes in many different material types, such as drilling cast iron, aluminum, copper, steel and stainless steel. Center drills have a short, stubby design, which eliminates the risk of deflection, making them the perfect tool for pre-drilling applications. When drilling a center hole on a lathe, accuracy is key, as the hole will ultimately remain aligned and stable during the process.

There are several advantages to using a center drill: Supporting the workpiece: Center drill holes can be used to support the workpiece on the lathe.

Creating a starting point: Center drills can be used to create a starting point for a larger hole. This helps prevent larger holes from shifting and eliminates deflection.

Countersinking: Center drills can be used as countersinking tools to make fasteners flush with the surface.

How to Choose Point Drills vs. Center Drill Bits

What is a Spot Drill?

A spot drill is used to create a small depression before drilling a hole with a twist drill bit. It acts as a locating point and guides the larger diameter drill to minimize the risk of deflection.

Spot drills and center drills are slightly different. Drill bit structure.

Center drill: The drill bit of a center drill is relatively short, usually only a few millimeters long, and the diameter is relatively small. The main purpose is to make an accurate center point on the workpiece.

Spot drill: The drill bit of a spot drill is relatively long, thicker than the drill bit of a center drill, and has the tip of the center drill head, which is convenient for accurate positioning and hole opening.

Drilling Accuracy

Center drill: Center drills are usually used for high-precision processing. Its drilling diameter is small, suitable for making an accurate center point or small hole on the workpiece. This helps to locate and open holes more accurately in subsequent processing.

Spot drill: Spot drills are used to drill larger holes than center drills. Although it also has a certain degree of accuracy, its accuracy is slightly lower than that of center drills. Unlike center drills, spot drills can be used for a variety of applications, such as spot drilling, chamfering, countersinking, V-grooving and engraving. They are made of high-speed steel or carbide and have different drill head angles, the most common of which are 90° or 120°.

Drill Bits

Why Use a Spot Drill?

As mentioned above, spot drilling has a variety of uses, the main use is to spot drill before drilling a hole, this process increases the accuracy of the secondary drilling. If the drill bit used is not self-centering, it is necessary to drill in situ. Because this minimizes the risk of the drill bit drifting.

Spot drilling can increase tool life and improve surface finish. It is worth noting that self-centering drill bits do not require situ drilling.

There are several advantages to using spot drills:

Accuracy: Spot drilling is very precise, which helps to ensure that the final hole is in the correct position.

Prevent drift: Spot drilling helps prevent the drill bit from drifting during secondary drilling.

Reduce heat: Spot drills generate less heat than ordinary drill bits, which helps prevent work hardening before drilling.

drill bit

How to Choose Between Spot Drills and Center Drills?

When on a conventional or CNC lathe, the center drill is the first choice for pre-drilling.

Spot drills are a great tool, and its function is no longer limited to drilling pilot holes for subsequent drilling. In addition, they can also be used as chamfers, and there are various fixed angles to choose from. The angles are available in 60°, 90°, and 120°, and can be used for a variety of processes, including: spotting, engraving, chamfering, and deburring edges.

The best way to choose between spot drills and center drills is to consider the following factors:

Purpose: What are you using the drill for? If you just want to make a small, precise hole, then a spot drill is a good choice. If you need to support a workpiece on a lathe or to create a starting point for a larger hole, then a center drill is a better choice.

Material: What material are you drilling? Spot drills and center drills can be made from high-speed steel and carbide. Both can drill a variety of materials.

Size: What size hole do you need to make? Spot drills and center drills come in a variety of sizes. Choose a drill that is the same size or slightly larger than the hole you need to drill.

Machine: Are you working on a lathe or a milling machine? If it is a lathe, then both options are suitable. However, on a milling machine, a spot drill is recommended.

end mill drill bit
In summary, both spot drills and center drills are useful tools for drilling holes in metal. However, they have different purposes and advantages. Spot drills are more precise and help prevent the drill from wandering when drilling a second time.

Center drills are used to drill a hole in a workpiece, in the case of windows, to support the workpiece and create a starting point for a larger diameter hole. The best way to choose between spot and center drill bits is to consider the drill bit’s intended use, the hole size you need and the machine tool you are working on.

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