1 What is twist drill
Twist drill is a tool used to drill round holes of workpiece by rotating cutting of its relative fixed axis. Because of its capacity chip groove into spiral shape and shape like hemp and named. Spiral grooves have 2, 3 or more grooves, but 2 grooves are the most common. Twist drill can be clamped on manual, electric hand-held drilling tools or drilling machines, milling machines, lathes and machining centers. Drill material is usually high - speed tool steel or carbide.
Twist drill specifications
Φ Φ 1.0, 2.5, 1.5, 2.0, Φ Φ Φ Φ 3.0, 3.2, 3.3, 3.5 and 3.8, Φ Φ Φ Φ 4.0, 4.2, 4.5 and 4.8, Φ Φ Φ Φ 5.5, 5.0, 5.2, Φ Φ Φ 5.8, Φ Φ 6.0, 6.2, 6.5, 6.8 and 7.0, Φ Φ Φ Φ 7.2, Φ 7.5, Φ Φ 7.8, 8.5, 8.0, 8.2, Φ Φ Φ Φ 8.8, 9.0, 9.2, 9.5 and 10.0, Φ Φ Φ Φ 10.2, 10.5, 11.0 and 12.0, Φ Φ Φ Φ 13.5, 12.5, 13.0, Φ Φ Φ 14.
Twist bit material
Twist drill material has 45# high carbon steel, used for soft wood, hard wood, soft metal, GCr15 bearing steel, used for cork and general iron, 4241# high speed steel, used for soft metal, iron and ordinary steel, 4341# high speed steel for soft metal, steel, iron, stainless steel, 9341# high speed steel for steel, iron, stainless steel, 6542# (M2) high speed steel is widely used in stainless steel, M35(cobalt high speed steel) is widely used in stainless steel. The most common difference is 45# steel, general with respect to 4241# high-speed steel, good point M2 is about the same.
4 Twist drill structure and Angle
Twist drill is a common drilling tool, which is composed of handle, neck and working part. Twist the basic Angle that twist drills includes vertex Angle, horizontal edge bevel Angle, before horn and hind horn 4 parts.
1, apex Angle
The Angle between two cutting edges of twist drill is called vertex Angle. The Angle is usually 118°. Drill soft material advisable smaller, drill hard material advisable larger.
2. Bevel Angle of the blade
The Angle between the horizontal edge and the main cutting edge is called the vertex Angle and is usually 55°. The bevel Angle of the edge varies with the Angle after grinding. When the back Angle is large, the bevel Angle of the edge decreases, the edge becomes longer, and the circumferential force increases when drilling. If the rear Angle is small, the reverse is true.
3, anterior horn
It is generally -30° to 30°, the largest at the outer edge, and becomes a negative rake Angle near the center of the bit. Twist drill helix Angle is bigger, front Angle is bigger also.
4, after Angle
The twist drill's back Angle also varies, with the smallest at the outer edge and the largest near the center of the bit. Generally, the value ranges from 8° to 12°.
5 twist drill and impact drill difference
Twist drill: a tool used to drill a round hole in a workpiece by rotating its relative fixed axis. Because of its capacity chip groove into spiral shape and shape like hemp and named. Spiral grooves have 2, 3 or more grooves, but 2 grooves are the most common. Twist drill can be clamped on manual, electric hand-held drilling tools or drilling machines, milling machines, lathes and machining centers. Drill material is usually high - speed tool steel or carbide.
Impact drill: Works by rotation and impact. A single shock is very slight, but a frequency of more than 40,000 shocks per minute can produce a continuous force. Can be used with natural stone or concrete. There is an adjustment knob at the bit collet when the impact drill works, which can be adjusted in two ways: ordinary hand electric drill and impact drill. But the impact drill is to use the inner shaft of the gear beat each other to achieve the impact effect, but the impact force is far less than the electric hammer. It is not suitable for drilling reinforced concrete.
Choice of twist bit
When the technician chooses the most appropriate bit type for a particular hole processing task, the aspect ratio of the bit needs to be calculated. The aspect ratio is the ratio of the depth of the hole being machined to the diameter of the bit. For example, if the bit diameter is 12.7mm and the hole depth to be machined is 38.1mm, the aspect ratio is 3:1. When the aspect ratio is about 4:1 or less, most standard twist bits will discharge the cuttings removed by the bit's cutting edge fairly smoothly from their grooves. When the aspect ratio exceeds this range, a specially designed deep hole bit is required to achieve effective machining. Once the aspect ratio of the hole being processed is greater than 4:1, it is difficult for standard twist drills to push chips out of the cutting zone and out of the hole.