Understanding Exit Burr in the Drilling Process

One of the chief difficulties in producing close tolerance holes in aircraft aluminum alloys is the problem of exit burrs. This synopsis provides an explanation of the reasons for this phenomenon, as it is observed. This writing is not the result of an empirical study. Instead, it is based upon close observation and experience. Additionally, there is no attempt to explain the complexities of metallurgy and its effects on the drilling process. The assumption is that aircraft aluminum has a malleable quality that is necessary in terms of its function. However, this same property leads to challenges under certain circumstances during drilling.

Exit burr occurs as a result of several factors; the following factors are the most significant:

1. 1)
   Material properties
2. 2)
   Cutter point geometry
3. 3)
   Coolant/lubricant supply
4. 4)
   Chip removal efficiency
5. 5)
   Mechanical stability of the set-up

Note: These same factors can be assumed to be significant considerations in overall hole qualities not exclusive to control of exit burrs.