An experimental investigation of the effects of point angle on the high-speed steel drills performance in drilling

Abstract

The differences in the cutting speed are a serious problem along the cutting edge of the drill, in drilling operations. This problem can partly be solved reducing the length of the cutting edge via changing the drill point angle. In addition, in this study, the effect of point angle, feed rate, and cutting speed on drilling is investigated. For identifying the optimum cutting parameters, AISI 1050 steel alloy was selected as the experimental specimen, these specimen were pre-drilled 5 mm in diameter due to eliminating the effect of the chisel edge. In the experiments, the holes were drilled only at a depth of 10 mm in order not to give any harm to the dynamometer while measuring thrust force. For this aim, in drilling process, drills with point angle of 100°, 118°, 136°, 154°, and 172° were selected. In conclusion, the thrust force, the tool wear, and the surface roughness linearly decreased with increasing point angles due to less removal chip area, in per revolve of the tool. However, the thrust force, the tool wear, and the surface roughness were adversely affected at higher feed rates and lower cutting speeds. The hole dimensional accuracy decreased at lower feed rates and cutting speeds but at higher point angles and concurrently at higher feed rates but lower point angles and cutting speeds. However, the hole dimensional accuracy showed more decisiveness at 118° than other point angles, while the highest dimensional accuracy values recorded at 136° point angle, at higher cutting speeds.

Feasibility of tool configuration and the effect of tool material, and tool geometry in multi-hole simultaneous drilling of Al2024

“…140º of carbide drill compares to the 118º point angle of HSS might have contributed to giving low surface roughness of holes. This is because the increased point angle caused the reduction in chip sizes, especially the undeformed chip thickness which resulted in low surface roughness [50]. However, to compare both the carbide drill with the same point angle of 140º but with different drill sizes, it was examined that the carbide drill with the lower size showed the low roughness.…”

“…In addition, Nouari et al [29] also preferred the use of carbide tools on HSS for dry drilling of Al2024. Other reasons might include the lower point angle of HSS drills which had an unfavourable effect on the drill wearing because the high point angle can result in a smaller cutting edge which caused the reduction in chip sizes and the thrust force [50]. Furthermore, the generation of high BUE using the 10 mm carbide drills was due to the formation of large chips whereas easy chip breaking and evacuation were found during a 6 mm carbide drill due to short size as aforementioned in the chips analysis.…”

Effect of high-speed steel screw drill geometry on cutting performance when machining austenitic stainless steel

“…When the point angle value of the CZ005 drill bit increased in the experiment, the feed force decreased. Some studies confirmed this conclusion 10 , 11 , however, the opposite dependence was presented in the studies 6 , 12 , 13 . When comparing the conditions of the individual experiments, it was found that the feed force decreased when the value of the point angle increased in the process of drilling into pre-drilled holes 10 , 11 , where the cross-cutting edge of the tool is not in contact with the workpiece.…”

“…The influence of the point angle setting on the achieved surface roughness of the drilled hole varies in individual studies. In the case of the studies 8 , 11 , they observed an increase in surface roughness when the value of the point angle increased, but contrary in studies 10 , 15 the authors presented a decrease in surface roughness when the point angle increased. In the study 16 , authors found that the surface roughness decreased about 20–30% when implementing ultrasonic drilling technology.…”

“…The dependence of the size of the point angle on the feed force varies in each study. It was found that when the point angle increased, the feed force slightly decreased 10 , 11 . The same trend was observed in the current study.…”