1. The hole straight poor
　　A. Spindle guide sleeve, arbor support sleeve, and so the center line of the workpiece support sleeve concentricity tolerance
　　B. Cutting edge geometry improper selection
　　C. Guide sleeve and tool the gap is too big
2. The pore size tolerance
　　A. Spindle guide sleeve, arbor support sleeve, and so the center line of the workpiece support sleeve concentricity tolerance
　　B. Cutting edge geometry improper selection
　　C. Gaps between the guide sleeve loose or the tool is too large
3. Poor surface quality
　　A. Improper size or geometry of the guide block
　　B. Cutting edge geometry improper selection
　　C. Cutting edges wear too much
　　D. guide sleeve loose or excessive wear
　　E. Arbor poor rigidity, excessive vibration
　　F. Cutting speed is too low
　　G. Cutting fluid filtration bad
　　H. Cutting fluid improper selection, guide block to produce adhesive wear
4. Low tool life
　　A. spindle guide sleeve. Arbor support sleeve, drill sets and other support center line concentricity tolerance
　　B. Blade poor wear resistance
　　C. Cutting edge geometry improper selection
　　D. Arbor poor rigidity, excessive vibration
　　E. Guide sleeve and tool the gap is too big, the knife fight at first drill
　　F. Inappropriate choice of cutting fluid
　　G. Cutting speed is too high, the blade wear fast　
　　H. Poor chip, chipping debris blocking
5. bad chip formation
　　A. CHIPBREAKER geometric shapes inappropriate
　　B. Blade geometry improper selection
　　C. Cutting speed is too low
　　D. The feed amount is too small or uneven
　　F. Uneven workpiece material