6 features of a sheet drill and its uses
Like step drills, sheet drills are used for cutting sheet metal. In this article you will find out which characteristics sheet drills have and which differences exist compared to step drills.
Sheet drills and step drills have a lot in common. They are both designed for use in sheet metal and are manufactured using the CBN process*. They also have many similar characteristics, especially at the tip of the drill. Although they are so similar, both precision tools have their reason for existence.
*CBN (cubic crystalline boron nitride) is much harder than conventional abrasive materials. Due to the higher hardness, the material structure is cut through smoothly during the grinding process and the cutting edges are therefore more accurate and sharp.
Point angles
The point angle is located at the head of the sheet drill. The angle between the two cutting edges is measured at the tip. A point angle is required so that the drill can center itself in the material.
The point angle of our sheet drills is 118°. The small point angle supports centering in the material. In the application, this means that no pre-drilling is necessary and you can drill the hole directly.
In our article "8 features of a twist drill and its functions" we discuss the point angle in more detail.
Point cut
For easy tapping, the sheet drill requires a corresponding pointing in addition to the small point angle.
The various point cuts are standardized in DIN 1412 shapes. Our sheet drills have a point split (form C). The point cut is also produced with the CBN grinding process.
Sheet drills with Form C center excellently in thin sheet metal and are suitable for drilling in solid and high-alloy steel.
Find more information about this topic in our article "Point cuts and point thinnings of twist drills for metal cutting".
Sheet drills have two cutting edges and chip flutes. The cutting edges with a straight groove cut the material.
Profile of flute (groove profile)
Due to its function as a channel system, the profile of flute promotes chip absorption and removal. It is important that the chips are removed quickly, as otherwise high heat will develop and the drill will burn out.
Sheet drills can have spiral and straight flutes.
Due to the CBN-deep-ground spiral grooves, the blades, in contrast to the conventionally milled flutes, are burr-free and sharp. The CBN ground flutes guarantee quiet running and high cutting performance.
Maximum diameter
The maximum drill diameter of the sheet drill can be straight, conical or have a stopper. Compared to a straight end, the cone eases the withdrawal from the drilled sheets.
A stopper prevents complete drilling through the drill hole. With the angle at the stopper, the drill hole can be countersunk.
Cone angle
The cone angle is measured between the drill core and the cutting edge. It is 20°-30° for sheet drills.
The continuous angle creates a conical hole wall in the borehole.
Shank
We differentiate between 3-way clamping surface shanks and bit shanks in our sheet drills. There are round shanks where the drill is more likely to spin in the chuck. The 3-way clamping surface shank prevents slippage in the drill chuck and makes the drill possible for use in hand drills.
The Bit shank (1/4" hexagonal shank) is ideal for use in cordless screwdrivers.
Applications
Sheet drills are suitable for cutting all standard industrial materials such as nonferrous metal, special steel, thermoplastics and duroplastics as well as sheet metals up to 4,0 mm thickness. You can center, tap and drill the sheet in one operation.
Sheet drills are mainly used in the following industries:
- electrical,
- sanitary engineering and heating technics,
- automotive
- mechanical engineering
- switching systems, and
- aviation.
Our sheet drills are available in diameters 3.0 to 22.5 mm.
One advantage of the sheet drill (and the step drill) is that it does not deform the workpiece during application. Compared to the twist drill with which the desired diameter is cut immediately, the sheet drill begins with a small diameter and cuts slowly to the desired diameter. As a result, a considerably lower force acts on the workpiece which is relieved and not bent.
For cutting metals use coolants and lubricants. This allows you to extend the service life of the sheet drill.
Also note when drilling that you
- do not press too hard (the sheet drill is pulled automatically into the plate) and
- adjust speed.
We carry sheet drills with tool steels HSS (also with TiN coating) and HSSE-Co 5. Depending on the tool steel and coating, harder or softer materials can be cut.
You can download speed table as PDF. Click on the picture.
Differences between sheet drills and step drills
| Sheet drill | Step drill | |
|---|---|---|
| Hole wall | conical | straight |
| Diameter | inaccurate, remeasurement is necessary | can be kept, thanks to the steps, accurately |
| In-between sizes | can be drilled | there are none between the individual steps |
| Deburring | only possible with stopper | next larger step can be used for deburring |
| Price | are cheaper than step drills | are more expensive than sheet drills |
If you want to know more about step drills, read our article "5 features of a step drill and its applications".
Conclusion and summary
Sheet drills are ideal for sheet metal processing up to a thickness of 4.0 mm. They are used in the electrical industry, sanitary and heating engineering, automotive industry (body construction), mechanical engineering, switch cabinet construction and aviation industry.
The higher hardness during the grinding process allows the production of sheet drills with the CBN process more accurate and chisel cutting edges. The material structure is cut through smoothly by the much harder abrasive material.
The point angle and the pointing ensure light centering and easier drilling into the workpiece. Sheet drills with their two cutting edges pull themselves into the sheet metal independently. The burr-free and sharp cutting edges cut the workpiece and remove the chip via the flute.
The cone angle is 20°-30° and leaves for n-between sizes a slightly conical hole wall.
When you use a sheet drill? You use it in sheets up to 4.0 mm thick, if:
- the exact measure of the diameter is not important to you (apart from the maximum diameter),
- you need a individual diameter,
- a conical hole wall for in-between sizes is accepted and
- you do not have to deburr the drilled hole (and if you do, you can still use the sheet drill with stopper and spot facer or a countersink in a further work step.
Sheet drills are available in different variants in the tool steels HSS (also with TiN coating) and HSSE-Co 5. You can find our complete product range of sheet drills at Products > Sheet drills.
If you have trouble finding the right sheet drill, please do not hesitate to contact us.