Measurement of Machined Surface Temperature in Drilling by Using Fiber-Coupled Pyrometer

Abstract

In drilling, excessive temperature rise is known to cause various types of thermal damage to the drill and workpiece. This paper presents a novel approach to measure the temperature variation on the machined surface at the bottom of the hole during drilling. A newly developed infrared radiation pyrometer equipped with two optical fibers is used to measure the temperature. One of the optical fibers is inserted through the oil hole of internal coolant carbide drill. It runs through the inside of the machine tool spindle and connects to the other optical fiber at the end of the spindle. Infrared rays radiating from the bottom of the hole during drilling are accepted and transmitted to the pyrometer by the two optical fibers. The workpiece thickness, spindle speed and feed rate are varied as experimental conditions. The temperature increases gradually as drilling progress and increases rapidly near the undersurface of the workpiece, possibly due to the reduced capacity of the workpiece to conduct heat away from the drill point. The temperature rise near the bottom of the workpiece effects on the rapid drill wear.