LEPEVNEY 6.9mm Drilling Dia Straight Shank Metric Twist Drill Bit HSS Cobalt Pack of 3

• Shank Diameter: 6.9mm；Total Length: 108mm / 4.3"
• Product Name: Straight Shank Twist Drill Bit; Package Content: 3pcs x Twist Drill Bit
• Material: HSS, Cobalt; Flute Length: 58mm / 2.3"
• Smooth groove finish, high hardness, wear resistance.
• Twist drills can be clamped on Manual, Electric Drills, Drill Presses, and Lathes; Suitable for Wood, Malleable Iron, Aluminum, Plastic etc.

Designed to be installed in the spring chuck of your spindle, these drill bits provide a secure and reliable clamping solution. The clamping length of the twist drill on the spring chuck ensures a firm grip, with a clamping length that is 4-5 times the diameter of the drill shank. To ensure precise and accurate drilling results, it's important to check the concentricity of the spindle and the collet, as well as the clamping force of the collet. Poor concentricity can lead to broken drills and inaccurate hole diameters, while inadequate clamping force can cause the actual speed to deviate from the set speed, resulting in slip between the chuck and the twist drill. Additionally, don't forget to check the spindle presser foot. It should have a stable contact surface, both horizontally and vertically aligned with the spindle. This ensures that your drilling process remains steady, preventing broken drills and offset holes.