Double Margin drills have an additional margin ground behind the leading margin, providing twice
the number of contact points. The second margin performs various functions to improve hole quality.
- The trailing margin burnishes the cavity, making a true hole and smoother finish, helping to provide a more concentric drilled hole
- A reamer finish can be achieved with double margin drills, eliminating a second operation.
- When a double margin drill is used with a drill bushing, the four margins locate in the bushing, providing increased bushing support in excess of 200%.
- When intermittent cutting is required, the double margin drill performs in two ways: Enhanced margin support in the first cavity cut, and support on breakthrough, which stops the drill from wandering when in contact with the work space.
- Drill back taper is more tightly controlled than a regular drill, enhancing a rounder hole location.
- 135-degree split point provides immediate self-centering on contact with the work piece, and reduces thrust, due to its notch-type web thinning at the chisel edge length. The split point is excellent for drilling harder materials (titanium, stainless steel, and high temperature alloys.)
- The bronze-gold drill color is an easy way to identify these tools as being cobalt aircraft drills, and is easy to group when resharpening.
- Will all these features incorporated in this double margin drill, it is excellent for hand drilling.