In 1983, Sumitomo Electric Hardmetal Corporation was the first company to succeed in developing drilling tools from carbide with an arc-shaped cutting edge that was an innovative design never before used for drills, Such innovation has led to the development of many industrial producs, including drilling oil holes in crank shafts, In the past, this was done using “Gun Drills” with a low drill speed and feed rate, which did not fulfill the nedds of mass production.
Recently, a new drilling tool has been developed called the “Long Multi Drilling, which has a speed (Vc) of up to 60-80 m/min and a feed rate (f) of 0.02-0.25 mm/rev. There are 2 points to be considered with this new drill; firstly, the workpiece requires preparation by using an endmill to make the bar become rounded and with a smooth finish and this is followed up by spot drilling with a 0.03-0.05 mm drill bit so that the “Long Multi Drill” can drill to a distance of 2-3 times the drill’s diameter. Secondly, we need to consider the drilling condition of this Multi Drill through using low speeds and a high feef rate at the beginning until the drill has reached 1 mm. before the holes’ bottom. Then, change the drill condition as recommend earlier with no need to stop for removing the chips, as the drill has been designed for easy chip removal. The final step is to remove the drill bit back from the hole using a low speed and high feed to prevent damage to the hole surface with the drill’s edge.
This is the drilling strategy for the “Long Multi Drill” that has provided satisfactory results with 2 time longer tool life and huge production cost reductions from real use by top automotive parts manufacturers in Thailand. Moreover, Sumitomo Electric Hardmetal Manufacturing (Thailand) can produce this “Long Multi Drill” at the same high quality and technology as Sumitomo Electric Hardmetal Corporation in Japan.