Gundrilling was developed about 150 years ago simultaneously by Russian and French gunsmiths. It was developed to provide a solution for manufacturing barrels that could withstand the high presurres of the new propellant nitrocellulose. This problem created a drive to come up with a material (steel) and a manufacturing process that could produce barrels of the quality that was required. Before gundrilling was invented, barrels were made by forging iron strips round a mandrel.
Before 1960s, the drilling head is made by HSS with heat treatment and grinding. Carbide replaced HSS rapidly. The carbide head is tapered on its length to reduce friction. The taper angle depends on the type of material o be drilled.For high precision drilling, the taper should be reduced to a minimum. Note that when the head is resharpened, the diameter of the drill changes, affecting the hole tolerance.
- Carbide blanks with single coolant hole
- Carbide blanks with twin coolant hole
- Carbide blanks with kidney coolant hole
|Blanks Dia. [mm]||L [mm]||Gundrill Dia. [mm]|
|6.5 - 31||330||6.0 - 30|