Date of Award
Fall 2002
Document Type
Dissertation - Restricted
Degree Name
Doctor of Philosophy (PhD)
Department
Mechanical Engineering
Abstract
Common metal removal processes include sawing, turning, milling, and drilling. Of the aforementioned processes, metal sawing has had the least scholarly investigation. Bandsawing and power hacksawing have seen some attention in the technical literature, but there has been very little focus on reciprocating sawing. The annual domestic market for portable reciprocating saws has grown to over 1 million units with accompanying annual metal cutting saw blade sales in excess of 50 million units [53]. Sawing is typically used to reduce the size of a larger piece of cast or formed metal so that it can be shaped by downstream processes such as turning or milling. Bandsaws perform this task well due to their continuous cutting action and forced feed rate. Portable reciprocating saws are generally used in environments where the workpiece not easily transportable. Reciprocating saws have lower cutting rates than handsaws, but their portability makes them convenient and necessary. Cutting rates depend not only on the machine, but also on saw blade geometry and workpiece material properties. The research documented herein was pursued to make a first contribution to the mechanics of reciprocating sawing with a comparison to prior work on bands awing and power hacksawing. Historical research on sawing has focused on the development of empirical constants to equate the relationship between process parameters and blade geometry to cutting rates of metals. Similar to past methodologies, experiments in this thesis are conducted to provide a basis for empirical relationships between cutting rates and saw blade geometry for reciprocating sawing. Additional experiments are designed to determine the effect of process parameters, such as reciprocating speed, stroke length, and applied thrust force, on the cutting rates of metals. ii The scope of this research also includes the derivation of anew analytical sawing model applicable not only to reciprocating sawing, but metal sawing in general. Particular attention is placed on the sawing rates of steel due to their broad commercial usage. The new model predicts cutting rates based on common process parameters and blade geometry. Application of the new sawing model allows users to predict cutting rates without costly experimentation, formerly necessary to develop empirical cutting constants. The analytical model for reciprocating sawing rates is compared to empirical studies over a wide range of process variables. A wear model for the cutting edges of saw blade teeth is also derived. Using a Design of Experiments technique, a test matrix is developed to determine the significance of applied thrust force and reciprocating speed on cutting rates of steel. Results of analytical predictions from the newly developed sawing model and empirical data compare reasonably well.