Chucks

The way you hold a gun drill determines the runout at the cutting tip. Runout affects hole diameter, straightness, surface finish, and tool life. I have used all three holding methods extensively and know the trade-offs. I choose the holding method based on the tolerance requirements and the number of diameter changes in the job. Here is my detailed comparison. Collet Holders Collets provide the most concentric holding of any method. A collet grips the drill shank evenly around its full circumference. Runout at the collet is typically 0.005-0.01mm if the collet is clean and the shank is ground accurately. ...

Workholding is more important in deep hole drilling than in most other machining operations. The cutting forces are high, the cycle times are long, and a part that shifts even 0.1mm during drilling can produce a scrap bore. I’ve used many workholding methods for deep hole drilling. Each has its place depending on the part geometry and production volume. Chucks Chucks are the standard method for holding round parts. A three-jaw or four-jaw chuck grips the OD of the part at the headstock end. The chuck provides the rotational drive if the workpiece rotates. ...