tailieunhanh - Drilling and Associated Technologies Part 1

Tham khảo tài liệu 'drilling and associated technologies part 1', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 3 Drilling and Associated Technologies In all things success depends upon previous preparation and without such preparation there is sure to be failure CONFUCIUS c550-c487BC Analects 88 Chapter 3 Drilling Technology Introduction to the Twist Drill s Development Drilling operations are perhaps the most popular machining process being undertaken today with their origins being traced back to cutting tool developments in North America in the 19th century. In 1864 toward the latter part of the American Civil War Steven Morse . later to design the significant Morse taper - for accurate location of the sleeved drills into their mating machine tool spindles founded the Morse Twist Drill and Machine Company in the North . Morse then proceeded to develop probably the most important cutting tool advance to date namely the ubiquitous twist drill. In Fig. 42 several of today s twist drills are illustrated along with just a small range of solid contemporary designs. Morse s originally-designed twist drill has changed very little over the last 150 years - since its conception. In comparison to the somewhat cruder-designed contemporary drills of that time Morse stated The common drill scrapes metal to be drilled while mine cuts the metal and discharges the chips and borings without clogging . Morse s statement was at best to some extent optimistic whereas the cold reality tells a different story as a drill s performance is influenced by a considerable number of factors most of which are listed in Fig. 43. Twist Drill Fundamentals The basic construction of a conventional twist drill is depicted in Fig. 44a. From this illustration two distinct cutting regions can be established firstly the main cutting edge or lips secondly at the intersection of the clearance and main cutting edge - termed the chisel edge. In fact for a twist drill the cutting process can be equated to that of a left-hand oblique turning tool where the rake and clearance face geometries are .