The spiral flutes are available in 2, 3 or more flutes, but 2 flutes are the most common. Twist drills can be clamped in manual, electric handheld drilling tools or drilling machines, milling machines, lathes and even machining centers. The drill material is usually high-speed tool steel or carbide.

The twist drill is a tool for drilling round holes in workpieces by rotating the cut relative to a fixed axis. It is named because its chip-containing groove is spiral and resembles a twist.

Twist drill use for industrial manufacturing on the most widely used type of drill, we generally use the twist drill. Drill length-to-diameter ratioWhen a technician selects the most appropriate type of drill for a particular holemaking task, the length-to-diameter ratio of the drill needs to be calculated.

The L/D ratio is the ratio of the depth of the hole being drilled to the diameter of the drill bit, for example, if the drill bit diameter is 12.7mm and the depth of the hole to be drilled is 38.1mm, then the L/D ratio is 3:1. When the L/D ratio is about 4:1 or less, the chip chute on most standard twist drills will discharge the chips removed by the cutting edge of the drill bit more smoothly.

When the L/D ratio exceeds the above range, specially designed deep hole drills are required to achieve effective processing. Twist drill standard products are adopted national standards, and the equivalent of international standards.

Once the length-to-diameter ratio of the hole being machined is greater than 4:1, it is difficult for a standard twist drill to remove chips from the cutting zone and discharge the hole, and the chips will soon block the chip chute of the drill bit, and then it is necessary to stop drilling, exit the drill bit from the hole, remove the chips in the chip chute, and then re-drill and continue to cut, and the above operation needs to be repeated several times to process the required hole depth, which is commonly known as "pecking". This drilling method is usually called "pecking" method.

Using the "pecking" method to process deep holes will shorten tool life, reduce machining efficiency, and affect the quality of the hole being processed. Each time the drill bit is withdrawn from the hole and reinserted into the hole after removing swarf, it may deviate from the centerline of the hole, thus making the hole diameter larger and out of the specified dimensional tolerances.

In order to solve the problem of deep-hole machining, in recent years, drill manufacturers have developed two new types of deep-hole machining drills - ordinary parabolic drills and wide-flute parabolic drills.

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Twist Drill Disadvantages

Twist drills have a more reasonable geometry than flat drills, but the following disadvantages still exist:

(1) Standard twist drill main cutting edge at various points on the front angle of the value of the internal and external difference is too large. Drill at the outer edge of the main cutting edge of the front angle of about +30 °; and close to the center of the drill, the front angle of about -30 °, near the center of the drill front angle is too small, resulting in large chip deformation, cutting resistance; and close to the outer edge of the front angle is too large, in the machining of hard materials, the strength of the cutting edge is often suspected of insufficient.

(2) cross blade is too long, the front angle of the cross blade is a large negative value, up to -5 4 ° ~ -6 0 °, which will produce a large axial force.

(3) Compared with other types of cutting tools, the main cutting edge of the standard twist drill is very long, which is not conducive to chip separation and chip breaking.

(4)The vice rear angle of the vice cutting edge at the edge band is zero value, which causes the friction between the vice rear face and the hole wall to increase, the cutting temperature to rise, the wear at the corner of the outer edge of the drill is larger, and the roughness of the machined surface deteriorates.

Twist drill use of maintenance

1, twist drill in use will first be inserted into the head of the drill head bar bolt connector activities connecting nut directional groove, counterclockwise tighten the connecting nut, can be inserted into the intended drilling area with hand pressure to clockwise to the spin into the soil, every spinning about 200 ~ 250 mm that is, upward to lift the drilling (if too deep to lift the dialing will be very laborious and not convenient). The soil in the spiral of the drill bit is picked off, and this soil is the soil sample at a distance from the site.

2, one by one back and forth to work to 1 meter when you need to continue to deep drilling, should be clockwise loosening the drill part of the connecting part of the connecting nut to remove the cross handle, the additional second section of the drill pipe part of the bolt head part of the connection inserted into the drill part of the movable connecting screw clockwise tighten the connecting nut, and then will be the cross handle parts and the drill pipe with the same as the above (1) than to continue to work, the three, four, five sections of the same as the above until the end of the work.

3, twist drill pipe is made of bushel-walled seamless steel pipe, so it is not suitable for use in hard soil areas.

4, after each use should be washed, dried, coated with anti-rust grease to prevent rust.

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