Tell you how to choose drill bits according to different purposes
Jun 24,2025
Drill bit is a widely used hardware component in construction machinery, used for drilling through holes or blind holes on solid materials, as well as expanding holes. However, different types of drills need to be selected for different operating environments. Common drills mainly include Fried Dough Twists drills, spot facers, center drills, deep hole drills and hollow drills. Although reaming and countersunking drills cannot drill holes in solid materials, they are commonly classified as drill bits.
The Fried Dough Twists drill is a hole processing tool, with a diameter of 0.25~80mm. It mainly consists of a working part and a handle. The working part has two spiral grooves in the shape of Fried Dough Twists, hence the name. The top angle of the cutting part of the standard Fried Dough Twists drill is 118 °, the oblique angle of the transverse edge is 40 °~60 °, and the rear angle is 8 °~20 °. The Fried Dough Twists drill has two types of shank: straight shank and taper shank. During processing, the straight shank is clamped in the drill chuck, and the taper shank is inserted in the taper hole of the machine tool spindle or tail; Generally, Fried Dough Twists drills are made of high-speed steel.
Deep hole drill usually refers to a tool used to machine holes with a depth to diameter ratio greater than 6. Commonly used ones include gun drills, BTA deep hole drills, jet drills, DF deep hole drills, etc.
The reamer has 3~4 cutter teeth, and its rigidity is better than that of Fried Dough Twists drill. It is used to expand existing holes and improve machining accuracy and smoothness.
A countersunk drill has multiple teeth and is used to shape the hole end into the desired shape using a forming method. It is used to process countersunk holes for various countersunk screws or to flatten the outer end face of the hole.
The center drill is used to drill the center hole of shaft workpiece. It is actually composed of Fried Dough Twists drill and spot facer with small spiral angle, so it is also called the composite center drill.
The middle of the drill rod of a hollow drill is empty, mainly used for drilling rock cores.
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