DLC-Coating

What Built-Up Edge Looks Like in Practice Built-up edge in aluminum gun drilling happens when the material welds to the cutting edge instead of flowing away as a chip. The welded material changes the effective geometry of the drill and causes poor surface finish. When I pull a drill out after seeing BUE, the cutting edge has a matte silver buildup that looks like cold-welded aluminum. The bore surface shows scratch marks and torn metal rather than the clean burnished finish I expect from gun drilling. ...

Problem Description Built-up edge in aluminum gun drilling shows up as a ragged, torn surface finish on the bore wall. I’ve pulled a 10 mm gun drill from a 7075-T6 block and found aluminum welded solid to the cutting edge, changing the effective geometry of the tool. The bore looked like it had been chewed out rather than cut, with surface finish readings jumping from 1.6 Ra to over 6.3 Ra. ...