## 1 Introduction  
The direct contact of the measuring contacts with the machined surface is one of the negative phenomena in measurement. One of the ways to solve this negative phenomenon is to use non-contact methods of measuring the parameters of machined surfaces. This article describes the suitability and new use of a laser triangulation sensor for measuring the deviation of the cylindrical surface diameter in the context of evaluating tool wear when turning C45 steel and optimizing cutting conditions. In this article, we present a new method for intermediate and final control of the measurement of quality parameters of the machined surface without removing the workpiece from the working area of the machine. In this way, it is possible to eliminate several errors in the inspection of products after machining. Currently, there are several companies in our region that produce various C45 steel shafts for agricultural and garden machinery. Several authors have used laser scanners in their research. These technologies can be used in different industries and in different applications [1]. [PERSON] et al. states that laser technology is one of the most advanced technologies and laser scanners are immediately used in industry [2]. [PERSON] et al. proposes a pneumatic for laser measurement system [3]. [PERSON] et al. state that sensors as information sources determine the quality level of information measurement and control systems [4]. According to [PERSON] et al. advanced systems for measuring parameters are important in terms of their various properties [5]. In selected studies, the authors have used LTS in machining, focusing mainly on the surface roughness parameter and surface defects. [PERSON] et al. describe the use of the laser triangulation method as one of the most modern methods for measuring product diameters [6]. [PERSON] et al. found that optical measurement systems are suitable for surface roughness evaluation [7]. In their research, [PERSON] et al. used laser deviation sensors in the evaluated real-time surface quality control based on cutting force, vibration, and acoustic emission signals [8]. The influence of the dynamic aspect of the cutting process on the machined surfaces was analyzed by [PERSON] et al. in their research [9]. [PERSON] et al. presented evaluation of surface roughness based on machining process [10]. [PERSON] et al. dealt with the optimization of parameters to predict defects in the manufacturing process [11]. [PERSON] et al. investigated the use of optical systems to identify defects in the production process [12]. Some authors have focused on solving positional accuracy of tools with LTS. Authors such as [PERSON] and [PERSON] et al. dealt with design of algorithms for determining the position of tools with the application of a triangulation sensor [13; 14]. [PERSON] et al. presented deviation measuring between the defined tool comparison position and the actual tool tip position [15]. [PERSON] et al. proposed a measurement method to determine linear stability for different real spindle speeds and virtual depths of cut using deviation sensors [16]. [PERSON] et al. present that laser sensors are widely used in automotive industry for position measurement [17]. [PERSON] et al. present a 6D multisensor measurement system for drilling robots in their paper [18]. [PERSON] et al. designed an optical system for measuring the position of tools during drilling [19]. Other authors also dealt with the use of LTS for vibration research and its effects on tool damage during machining. [PERSON] et al. proposed a new experimental method for estimating the vibrations of the milling cutter with a laser sensor [20]. [PERSON] et al. described and proposed an innovative algorithm for early detection of tool damage [21]. In the research, [PERSON] et al. analyzed various signal functions that affect the wear of a tool, filtering out unwanted signals [22]. [PERSON] et al. investigated the possibilities of using sensors to evaluate roundness deviations [23].