Why do you need a “carrot”: interesting features of step drills

Conical step drills replace an entire set for metal processing, including crowns. They are needed to produce precise holes on materials up to 6 mm thick. One of the main advantages is the quality of the edge. The holes are neat, without burrs, even with a metal thickness of 1 mm. Using such drills, plastic and wooden sheets and drywall are also processed.

Features of Step Drill

In everyday life, a conical drill with steps is called a “carrot” or “stepping”. The tool has a specific structure in the form of translational channels. Each subsequent channel has a larger diameter. The transition is 35–45 degrees.

The stepped structure increases the efficiency of drilling thin metal by 50%. The cutting ability of the drill is enhanced and the smoothness of processing is significantly increased.

Photo of step drill:

The tip of the cone consists of a tip for pre-drilling, a first bevel that removes burrs, and a special cutting edge that widens the hole.

To increase cutting capabilities, steel is often coated with an abrasive coating - titanium or diamond chips.

Application

Step drills are most widely used in car repair, plumbing installation, electrical wiring, construction and finishing work.

What are they needed for?

• Drilling thin sheet materials.Conventional drills are not suitable for obtaining perfectly round holes in thin sheets: they easily deform the material and leave torn edges. In this case, you can use a set of core drills... or just one step drill. “Carrot” is better because it makes holes in one operation.
• Correction of defects: triangular holes, burrs, alignment problems and others.
• Grinding the finished hole. Using a tool, remove chips. That is, the drill replaces the needle file and angle grinder.
• All types of work. Step drills are universal. They are suitable for any type of work and replace a whole set of drills and some other tools (for example, centering elements).

It should be taken into account that step drills have special operating rules. Only a strictly vertical stroke is allowed. It is equally important to comply with the speed limit. For steel it varies from 200 to 1000 revolutions. The larger the diameter, the lower the speed should be.

Experienced craftsmen also advise using a cooling emulsion when drilling. And if you need to drill through a thin sheet, place a piece of unnecessary plywood 10–12 mm thick under the piece of iron. When drilling aluminum and other tough metals, the hole area is lubricated with machine oil.

Advantages and disadvantages

Step drills could be called ideal if not for a couple of negative aspects.

Let's start with something pleasant. Step drill:

• gives perfectly clean holes with a small material thickness;
• performs several operations at once: drills, chamfers, cuts, grinds;
• has several drill diameters in one;
• the sharp tip easily penetrates the material, regardless of its density and structure;
• can be used in drilling tools with automated and manual drive;
• As a rule, it is characterized by increased strength and does not dull for a long time.

Step drills have few disadvantages, but all are quite significant:

• High price. A high-quality nozzle costs 2000 rubles. and higher. The cost is determined by the quality of the steel, the presence of spraying, the brand, as well as the operating range. The more diameters, the higher the price. The cheapest Chinese nozzles cost from 400 rubles.
• The device is ineffective in situations where you need to drill holes in materials thicker than 6–10 mm.
• Requires careful handling. Great force, misalignment, or a fall from a height can lead to deformation. Then all higher diameters will become unavailable.

Kinds

Step drills differ in type of material, shape, size (working range). For the manufacture of tools, high-speed steel HSS is used. It can be further processed or sprayed.

The strength of the product can be judged by its color:

• gray – steel without reinforcement;
• black – hardened steel;
• yellow – addition of cobalt;
• bright gold – titanium nitride coating (ensures maximum service life).

According to the shape of the stepped type nozzles there are:

• ordinary;
• without guide point;
• of two conical parts with different angles of inclination to the surface;
• with 1–3 grooves;
• with straight grooves and spiral grooves.

The spiral shape of the grooves increases the efficiency of the tool. Moreover, the more there are, the higher the speed can be used.

The sizes of the nozzles are very different. They differ in the number and height of steps, and the size of the starting diameter. The minimum first size is 4 mm. One drill can consist of 5–15 steps and start with different diameters.The standard step height is 5 mm (from 3 to 6 mm).

The step range of 6–38 mm covers almost all domestic drilling needs.

Questions and answers

What to look for when buying a step drill?

The working diameter and type of material are critical. The steel must meet the requirements of GOST. Experts advise taking nozzles from proven brands - Izar, Bosch, UniBit, Irwin/Hanson. They also point out that 7 stages of 20 mm drills better and longer than 7 stages of 32 mm. You should not chase large diameters unless absolutely necessary. Smaller diameters are always used and therefore wear out faster. It may turn out that it will not be possible to reach large diameters.

Can step drills be sharpened?

Only a few, mostly in the low price category, and with slight deformation. Straight edge bits are easier to sharpen, while spiral bits require special equipment. As for expensive drills, they cannot be sharpened. A striking example is drills coated with titanium nitride (rich golden color). It is important to note that they retain excellent cutting ability for a long time. Therefore, in principle, they do not need sharpening.

So, the main purpose of a step drill is to drill large-diameter holes in thin metal (in electrical panels, cars, etc.). However, the nozzle can be used for both hard and soft materials: wood, drywall, plywood, plastic. It eliminates the need to carry around a set of drills of different diameters. Many craftsmen are stopped from buying only one thing - the high cost of the product.