The single ﬂute gundrill, with its ability to machine very straight deep holes and hold excellent ﬁnishes, was originally developed for gun barrel manufacturing. Today, this tool is a general-purpose drill designed for deep hole drilling in virtually any material.
The gundrill requires high-pressure coolant through the tool, keeping the cutting edges lubricated and allowing for adequate chip evacuation down the ﬂute channel. Star SU’s Single ﬂute gundrill product line diameter range is .078” [1.98mm] through 1.500” [38.10mm] as a solid carbide head.
Larger diameter tools are available using a brazed inserted blade design. All gundrills can be made to any speciﬁc length. Lengths over 72” [1828 mm] will have an additional weld joint in the body of the tool.
The gundrill is designed to drill holes from the solid, obtain bottom hole conﬁgurations, and assist in burr free intersections. The gundrill can achieve precision holes in one pass thus eliminating the need for secondary passes, and is a tool for consistent hole-to-hole reproduction.
This tool is unique in its limitations, for machining deep holes are limited to the ﬂute length not the depth of the cut. The design of the single-lip, straight deep “V” ﬂutes and high coolant pressure allows for fast, consistent penetration without the need for pecking.
Due to the point not being on center, the tool requires either a bushing or a pilot hole. Once into the cut, the tool is self-piloting. The additional advantages of a single ﬂute gundrill:
- Straightness tolerance of .001” [0.03mm] per inch
- Finish hole diameters as good as +/- .0005” [0.013mm]
Star offers three different styles of coolant hole conﬁgurations:
- Kidney Shaped Hole (KDS) – This style is recommended for cutting diameters under .375" [9,53mm]. Extruded shapes assist in achieving larger gallons per minute out of the front of the tool, thus allowing for better chip evacuation. This coolant hole conﬁguration also can assist when lubricity is minimal.
- Single hole (GDS) - This style is used when the environment is in best conditions. This means that application has adequate pressures.
- Dual Hole Conﬁguration (TCH) – This coolant hole design is recommended for cutting diameters .376" [9,54mm] and greater. This design allows for higher ﬂows assisting in better chip evacuation.