α Alpha —- Lip Relief Angle
β Beta —- Wedge Angle
γ Gamma —- Land Angle
σ Sigma —- Point Angle
ψ Psi —- Chisel Edge Angle
The best chisel edge angle between 52 ° – 58 °
The above angle depends on the processing material.
The dimension precision and surface roughness of drilling, and drilling efficiency are directly related to the quality of cutter sharpening and re-grinding of twist drill.
(a) Grinding Correctly
(b) Point angle asymmetry
(c) Different Length of Cutter Grinding
(d) Point angle and Cutter Grinding are asymmetric
In the process of metal cutting, twist drill cuts the metal layer on the workpiece, at the same time, the workpiece and chips acts on the twist drill, causing the twist drill wear off. Normal wear off is inevitable, but abnormal wear is not acceptable. Such as abnormal wear on corner part of twist drill, Now, PURROS Machinery will enumerate these questions, and how to solve them.
In production, chipping of corner edge twist drill is happened many times. Because of drill material, loose jig, uneven hardness of workpiece material, unsuitable feed speed, unsuitable coolant, relief angle too small, or exhausted bit, etc.
Situation 1: Continue reading
Definition of Ni Zhifu Ordinary Twist Drill Bit: Based on standard twist drill that the cutting part is grinded onto a special shaped drill bit. The standard twist drill consist of two major cutting lips (major cutting edges) and a chisel edge. The most fatal weakness is that the negative front angle of chisel edge and dead center are larger, led to the cutting conditions are unfavorable. Ni Zhifu Ordinary Twist Drill Bit is that grinding two symmetrical crescent grooves based on standard twist drill, forming arc blade, and then sharpening two inner straight edges on the chisel edge and dead center. After that, with the chisel edge and original two straight edges, making the standard twist drill into “Three knife-points and seven knife-edges” that is the Ni Zhifu Ordinary Twist Drill Bit.Continue reading
In actual work, we will encounter some special machining phenomenon, such as machining a larger diameter hole, or bottom of hole should beflat. Today, here we introduce reaming and countersinking, let’s go.