Excerpt from Modern Drilling Practice: A Treatise on the Use of Various Type of Single and Multiple Sindle Drilling Machines, Including Their Application to Standard and Special Operations, the Relation of Speeds and Feeds to Intensive Production, and the Different Types of Tools and Fixtu

During recent years, a number of important changes have been made in methods of drilling holes in the parts of manufactured products. Noteworthy among these are the great increase in the speed at which twist drills are driven, the application of various types of universal or special multiple-spindle drilling machines or auxiliary drill heads, and the successful employment of semi-automatic drilling machines. All of these developments in drilling practice have been introduced with the view of increasing rates of production, and, in preparing the subject matter of this book, the author's object has been the same. The methods discussed are those which have been thoroughly tried out under actual manufacturing conditions, so that their practicability has been conclusively demonstrated. As a result, men who are responsible for the selection of methods of performing machining operations can decide upon the application of any of these suggestions for handling their own work with complete assurance that the resulting benefits are likely to be as great as in the case of other plants where substantial economies have been effected.

Probably it is safe to say that there is no class of cutting tool used in machine shops which receives as little consideration as the twist drill. This is largely due to the fact that drills can be bought ready for use in practically any size. As a result, the mechanic is likely to assume that the twist drill manufacturer has produced tools which are not only ready for use, but which are capable of remaining in good condition with very little attention. As a matter of fact, the proper grinding of a twist drill is of the utmost importance, and unless the drill is ground to the proper shape, its cutting efficiency is certain to be very seriously impaired.

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