Theoretical investigation of kickback in diamond chainsaw and circular cut-off saw

Abstract

Over 23,000 chainsaw-related injuries are reported annually. Most of these accidents occur due to kickback that is described as an abrupt motion of the guide bar or cutting blade towards the operator. Despite the fact that early studies of this extremely dangerous phenomenon date back to the previous century, most of the available literature is limited to wood cutting chainsaws that are chip-forming, while kickback initiation mechanisms are not well understood for abrasive saws that are typically utilized for cutting hard materials, such as metal, tile and concrete. In this thesis, two distinct kickback initiation mechanisms are studied by the development of four theoretical models that incorporate increasing levels of complexity. These models are then solved numerically to simulate kickback events and to reveal their sensitivity to both the design parameters of the saw and the cutting configuration. Inspired by the modeling, lab tests have been carried out with a specially designed kickback test rig. A comparison between the experimental data and the simulation results is then conducted. It is shown that when cutting hard materials via an abrasive saw, energy transfer in a kickback event is linearly dependent on the normal force that is applied by the user. This sensitivity to the user applied loading and to the cutting configuration is also revealed by a dimensionless analysis that shows a significant effect of the saw design parameters and human factors. For future studies, improvements on the current test rig are required to better account for the human-saw interaction. The out-of-plane motion of the saw also poses a potential risk and requires further investigation to provide guidance for safer practice.