What Is A Twist Drill?

Twist drills (also commonly referred to as twist bits) are the most widely used of all drill bit types. Twist drills will cut anything from wood and plastic to steel and concrete. They are most frequently used for metal cutting, and they are generally made from M2 high-speed steel. At diameters up to about 1/2", twist drills are not only the cheapest of all bits a woodworker could use but also offer the widest selection of sizes. Although they are designed for cutting metal, they also work quite well in wood. 

A twist drill is a metal rod of a specific diameter that has two, three, or four spiral flutes running most of its length. Two-flute drills are for primary drilling, whereas three- and four-flute drills are only for enlarging cast or punched holes in a production situation. The section between the two flutes is called the web, and a point is formed by relief grinding the web to an angle of 59° from the drill's axis, which is 118° inclusive. This forms a sloped cutting edge at the edge of the flute, which is called the lip. A twist drill is very inefficient at the point because the web leaves scant exit space for debris (called swarf) and because the point has a low surface speed compared to the periphery. For this reason, a good scheme for drilling larger holes is to first drill 1/4” or less and then follow with the drill of the desired diameter.

Materials: General purpose twist drills for use in portable drills are available in different grades of high-speed steel as well as cobalt steel and solid carbide. Twist drill bits for automated machinery are available in carbon steel, high-speed steel, carbide tipped, and solid carbide.

Coatings: General purpose drill bits are available with black oxide, bronze oxide, a combination of black and bronze oxide, and TiN coatings. Twist drills for automated machinery on our site are primarily for use in wood or plastics and are not coated.

There are different twist drills designed for different applications. But even the right twist drill for the intended application can break if used incorrectly. This can have different reasons which we have summarized below.

Twist drills are designed for various applications. Depending on whether you want to drill in structural steel or high-strength steel, you must select the appropriate drill. If you do not do this, the drill may break.

We list eight reasons why drills can break:

1. Using the wrong drill for the material to be drilled

2. Workpiece and drill were not clamped firmly enough

3. Poor chip removal

4. Cutting speed and feed rate set incorrectly

5. Poor quality of the drill

6. Small/large diameter of the twist drill

7. No cooling

8. Using the drill in a handheld drill instead of a pillar drill

If you pay attention to the issues, your drills should be undamaged and remain with you for a long time.

Solid Carbide Twist Drills Bits are cutting tools for creating circular holes in the workpiece. We supply high-quality carbide rods for making carbide twist drills. If you are looking for a superior carbide rod, contact ZZBETTER to get free samples.