Gun drill is considered to be used when the hole depth with diameter range of 2.0~50mm up to or exceeds ten times the diameter, as the gun drill provides high hole precision, accurate hole position, excellent hole surface finishes, good straightness and concentricity. It can be easily applied to process various kinds of deep holes, and also an ideal solution for the special deep holes, such as cross-holes, blind holes and flat-bottomed blind holes etc. Since the total length of gun drill can reach to 5000mm, multiple supports of tool required to ensure the stability of machining with distance no more than 40-50 times the diameter of the gun drill.
link:http://www.mariejcarbide.com/carbide-rod/tungsten-carbide-gun-drill/