Gun Drill Holding Methods: Collets, Chucks, and Sleeves
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. ...