Influence of the drill bit tip geometry on the rotary drilling process performed with a hand-held hydraulic drill

In the mining and construction industries, hand drills are used to carry out many processes related to excavation and auxiliary works. Hand drilling is commonly applied for making small diameter holes, especially in hard-to-reach places. In the case of manual drilling, an important parameter is drilling resistance, especially torque. Drilling tools are subject to wear, which has a negative impact on the process of drilling, including resistance and efficiency. A blunt tool lowers the drilling speed and puts more strain on the operator. The article presents the results of laboratory tests of selected parameters of the drilling process carried out with a hydraulic rotary drill. The tests were performed with the use of new drill bits as well as drills characterized by a various degree of wear. The tests were carried out for popular, frequently applied rotary drilling tools, on a unique laboratory stand that enabled setting the feed force and measuring the torque, rotational speed, drilling path, drilling speed as well as the in and out pressure of the drill. A number of characteristics were determined as a function of time and depth of the drilled hole. It was found that tool blunting affects the drilling process in various ways, whereas the intensity of this influence is determined by the type of blunting. The test results can provide a basis for developing a criterion for replacing a drill bit with a new one.