International Conference on Mechanical, Automobile and Robotics Engineering (ICMAR'2012) December 14-15, 2012 Singapore

Surface Topography Characterization of Surfaces Fabricated by Linear vs. Angular and Hand Scraping.

Tejas Bhosale, Rahul Waikar.

specimen to qualify with respect to the required surface finish. Abstract— A light weight and portable automatic linear scraping Automation of scraping process has been achieved by using tool powered by an oscillating motor was developed to substitute the robotic arms and computer controlled grinding wheels [7]. traditional hand scraping process. Its performance in terms of surface However such methods can scrape jobs of fixed size and finish and material removal rate was compared with the commercially available angular scraping and hand scraping shape. In order to facilitate scraping irrespective of the job technique. Mild steel blocks finished by face milling were subjected nature, a portable tool holder configuration is developed that to the three types of scraping. 2D surface profiles and the material mechanizes linear scraping, thereby reducing dependence on removal rates of resulting surfaces were measured. The results point operator skill and reducing operator effort. In this work the out to linear scraping as the best among the three scraping processes linear scraping configuration is compared with the widely as the resulting surface parameters (Ra, Rq, Rpk, Rk and Rvk) are available angular scraping configuration, highlighting its superior to the other two processes. Hence the resulting surface can give better tribological performance as it can be less susceptible to distinct advantages. The paper mainly focuses on the wear. The linear scraping tool was also found ergonomic better than comparison of surfaces generated by linear scraping with hand hand scraping and angular scraping by reducing operator effort and scraping and angular scraping in terms of the surface increasing the scraping efficiency. topography obtained by an individual high point, and material removal rate. In addition, the paper specifies the Keywords—metal scraping, surface roughness, abbott curves, ergonomic advantages of the linear scraping configuration ergonomics. over the angular scraping and the hand scraping. The paper finally explores the performance range of the scraping process I. INTRODUCTION and its limitations and advantages as a finishing process. AND Scraping is an art which is mastered by years of Hpractice with the objective of removing precise amount II. EXPERIMENTAL SETUP AND PROCEDURE of material so as to alter the geometry of the areas for matching surfaces [1]-[3]. It requires great skill so as to A. Linear scraping and Angular scraping tool maintain optimum pressure throughout the stroke. The effects of human skill variations become predominant in areas where surfaces need to mate with precision. In such cases the tribological properties of the surfaces are governed by the quality of the surface finish [4]. The blue matching procedure for scraping involves use of markers that transfer the geometrical profiles from the master to the specimen surface that needs to be scraped so as to reveal the number of high points or peak points per inch (PPI) and the percentage of points (POP) [5], [6]. Firstly the areas highlighted through Fig. 1 Top view of scraping machines representing the AS and LS configurations (schematic). blue matching must be scraped only up to the required extent.

Secondly the adequately scraped high point must help the The schematic top view of the Angular Scraping (AS) and Linear Scraping (LS) is shown in Fig. 1. The Angular Tejas Bhosale is with the Department of Industrial and Production Engineering, Vishwakarma Institute of Technology, Pune, MH 411037 Scraping is a widely used configuration in which the direction INDIA. of oscillations is perpendicular to the feed of the scraper. Rahul Waikar was with the University of Alabama, Tuscaloosa, AL 35404 Material is removed in the form of ridges with this type of USA. He is now with the Department of Industrial and Production Engineering, Vishwakarma Institute of Technology, Pune, MH 411037 INDIA configuration. On the other hand, as shown in Fig. 1 (b), the (phone:+91-2024202272; fax:+91-2024280926; e-mail: tool holder in LS configuration is designed to give the [email protected]). direction of the oscillations same as the direction of the feed

and hence the name Linear Scraping.

165 International Conference on Mechanical, Automobile and Robotics Engineering (ICMAR'2012) December 14-15, 2012 Singapore

The LS assembly uses the oscillatory output of a 2.5 A and was machined was noted. This set of processes was designated 120 V motor shaft to give 8000 oscillation per minute (OPM) as Scraping Round 1 (SR1). The blocks were scraped to obtain at no load condition. The mild steel tool holder weighs 80g a smooth and a uniform surface. The scraping process did not and on coupling to the motor oscillates at 7500 OPM (loaded completely remove the underlying milling feed marks. The condition). Since the arc swept by the cutting tool is only 2.8 weight of the blocks after SR1 was noted and designated as degrees its motion can be approximated to linear oscillatory W1; time for each sample was noted and designated as T1 and motion. the surface topography parameters created by the SR1 process was designated as SF1. The SF1 values are show in Table II. B. LS Tool Holder Design and Assumptions The blocks were then again subjected to scraping in the The scraping used in LS configuration is the same same order as stated above. This time scraping was done to tool used in hand scrapers. It is made from M2 tool steel and entirely remove the milling feed marks on the surface. This set is 25 mm by 28 mm in size with a thickness of 2.15 mm. of processes was designated as Scraping Round 2 (SR2). The Cutting force calculations are done assuming the tool to be a weight of the blocks after SR2 was noted and designated as single point cutting tool. This is because the cutting edge of W2. Time for each sample was noted and designated as T2. the tool bit is an arc with the middle portion protruding The surface finish created by the SR2 process was measured forward due to which the metal first comes in contact with the and designated as SF2. The SF1 values are show in Table III. tool at this point. The chances of the tool or tool holder failure The material removal rates for SR1 and SR2 are calculated are highest at this point and hence the assumption. Apart from and shown in Table IV and Table V respectively. this orthogonal cutting is assumed since the cutting edge is perpendicular to the direction of scraping. The cutting force is calculated using the Merchant Force circle diagram and the III. EXPERIMENT RESULTS strength calculations for the links of the tool holder are done TABLE I using the Flexural formula. The maximum stress developed in SURFACE FINISH0 Position Ra Rq Rt the tool holder was less than the yield strength of steel due to Job Name Rsk which mild steel was chosen as the fabrication material. Number (μm) (μm) (μm) Resilience & Stiffness are not considered since the cutting 1 1.545 1.951 10.892 -0.11 force and the bending moment values are on the lower side. A 2 1.825 2.235 12.57 0.048 3 1.731 2.151 12.176 -0.291 C. Experiment Procedure The aim of the experiment was to quantify the performance 1 1.544 1.944 11.86 -0.203 B 2 1.403 1.755 9.996 0.213 of the machine equipped with linear scraping (LS) 3 1.78 2.121 11.004 -0.033 configuration and compare it with those of the hand scraping

(HS) and the angular scraping configuration (AS). The 1 1.796 2.184 12.774 -0.085 scraping involved in the experimental procedure was C 2 2.009 2.414 12.296 -0.191 performed by a skilled worker who was trained to use both the 3 1.673 2.063 11.182 -0.353 configurations and at hand scraping. The quality of the surface generated by the processes was measured by using a “Dektak TABLE II 150” surface profilometer (contact type) of “Veeco” make. SURFACE FINISH1 The traces were taken at three positions for each samples and Type of Job Position Ra Rq Rt Machinin Rsk the sampling length for each position was 5 mm. Name Number (μm) (μm) (μm) Three mild steel blocks of size 50 mm × 40 mm × 18 mm g were chosen as the material for scraping and were named as 1 0.205 0.233 1.007 0 × A LS 2 0.225 0.256 1.213 0.24 A, B and C. One surface (50 mm 40 mm) of each block was 3 0.296 0.344 1.225 -0.1 face milled at a cutting speed of 120 SFM and 0.25 mm as the depth of cut to obtain a semi finished surface on which the 1 3.795 4.632 27.872 -0.19 further experimentation of scraping was done. The weight of B AS 2 4.506 6.054 36.298 0.14 the blocks was noted and designated as W 0 and the quality of 3 3.695 4.412 21.708 -0.05 the surfaces created by the milling process was measured using a surface profilometer and designated as SF0. The 1 1.17 1.454 6.35 -1 parameters are abbreviated as follows throughout the paper: C HS 2 1.867 2.397 11.882 -0.79 Ra: Arithmetical Mean Deviation or Average Roughness, Rq: 3 1.339 1.627 7.394 -0.27 Root Mean Square Roughness, Rt: Maximum peak to valley height, Rsk: Skewness. The detail of these parameters can be found in other references [8]. The Ra, Rq, and Rt values are expressed in (μm) throughout the paper. The SF0 values are show in Table I. The blocks were then subjected to the following types of scraping: A: Linear Scraping (LS), B: Angular Scraping (AS) and C: Hand Scraping (HS). The time for which each block

166 International Conference on Mechanical, Automobile and Robotics Engineering (ICMAR'2012) December 14-15, 2012 Singapore

TABLE III is seen in Table II that the Ra value is the least for the Linear SURFACE FINISH2 Scraping (LS) process. A mediocre decrease in Ra is observed Job Type of Position Ra Rq Rt for Hand Scraping (HS) when compared to that obtained by Rsk Name Machining Number (μm) (μm) (μm) milling. On the other hand, Angular Scraping (AS) has 1 1.644 2.336 16.117 -0.27 resulted in an increased Ra value. The Rq or the root mean A LS 2 1.034 1.293 5.655 -0.46 square parameter is more sensitive to variations than the Ra 3 0.803 1.09 5.618 -1.14 parameter since the amplitude is squared in this case. Lower values of 0.23-0.35 μm are observed for LS where as AS 1 2.626 3.068 14.751 -0.02 B AS 2 2.857 3.549 14.082 -0.31 shows higher values of 4.4 to 6.05 μm. The maximum peak to 3 1.969 2.543 13.367 -0.01 valley height for AS is 26 to 36 times than that of LS. HS results in Rt values that are 6 to 11 times that of LS. 1 2.439 3.466 20.676 -1.99 The probable reasons for obtaining a better surface finish C HS 2 0.829 1.066 6.383 -1.17 with LS are as follows. The oscillation rate or the strokes per 3 2.468 3.27 18.376 -1.26 minute (SPM) for the LS configuration is 7500 whereas hand scraping is usually performed at 110 SPM for optimized TABLE IV performance. The stroke length of LS configuration is MATERIAL REMOVAL RATE1 ΔW ΔV T MRR 0.32mm whereas the stroke length of hand scraping is Job M/C W (g) W (g) 1 1 1 1 0 1 (g) (mm3) (s) (mm3/s) generally equal to 30mm. A smaller stroke length prevents A LS 301.09 301.02 0.07 8.917 49 0.182 vibrations and chattering which generally disturb surface B AS 300.34 300.26 0.08 10.19 47 0.217 topography in metal cutting. A smaller stroke length also C HS 299.45 299.44 0.01 1.273 37 0.034 ensures uniform application of pressure throughout the stroke which results in uniform removal of material. Since the LS TABLE V assembly is made up of rigid material (mild steel), a constant MATERIAL REMOVAL RATE2 cutting angle of the tool is maintained with the surface MRR 2 Jo ΔW2 ΔV2 T2 3 M/C W1 (g) W2 (g) 3 (mm /s throughout the stroke. This is generally difficult to achieve in b (g) (mm ) (s) ) hand scraping. A LS 301.02 300.76 0.26 33.121 145 0.229 Fig. 2, Fig. 3, Fig. 4 and Fig. 5 are graphs which show the B AS 300.26 299.95 0.31 39.49 151 0.261 profile traced by the stylus of the surface profilometer on the C HS 299.44 299.36 0.08 10.191 195 0.052 scraped surfaces. In all the graphs that are presented, the X-

TABLE VI axis is in micrometers and the vertical axis is in nanometers. BEARING RATIO CHART The length of the horizontal axis is equal to the sampling length which is 5000 micrometers. Fig. 2 shows the output of Bearing Ratio in percent at Rpk/ Rvk/ Job M/C Pos. the surface profilometer for one of the sampling positions of respective percent depths Rk Rk avg. avg. the LS configuration for SR1. It is seen, that the graph is 20% 40% 60% 80% symmetric about the reference line or the zero line. Same 1 23.84 42.88 75 95.38 SR holds true for all the graphs of the SR2 process for the LS A 1 2 43.46 64.2 94.23 98.84 0.12 0.27 LS configuration. 3 30.57 75.38 97.11 99.23

1 10.57 25.38 62.88 94.04 SR C 1 2 12.88 35.38 66.34 89.42 0.29 0.20 HS 3 7.5 40 77.11 95.77

1 1.15 25.19 89.23 97.5 SR A 2 2 21.15 67.69 83.65 95.55 0.25 0.60 LS 3 9.8 44.8 80.38 95.96

1 47.5 80.19 96.5 98.46 SR C 2 2 22.3 69.23 93.07 98.26 0.32 0.43 HS 3 23.05 73.07 95.55 98.84 Fig. 2 LS Process graph. IV. RESULTS DISCUSSIONS However the HS graph is predominantly below the A. Comparing Parameters of the surface created by SR1 reference zero line for both the SR1 and SR2 processes. We The samples were milled so as to bring all the jobs on the may conclude that hand scraping mostly tends to favor valley same reference level so that the scraping process executed on generation without high peaks as seen in Fig. 3 whereas LS them could be evaluated and compared. The Ra values in creates a balanced surface. This may be one of the main Table I show that milling provided a comparable finish to all reasons for obtaining a lower Ra value when the material is the three samples. After executing Scraping Round 1 (SR1) it subjected to LS. However it must be noted that the nature of

167 International Conference on Mechanical, Automobile and Robotics Engineering (ICMAR'2012) December 14-15, 2012 Singapore valleys with respect to the core roughness or the plane region overall surface quality has declined for all the three processes. must also be considered which is discussed later. The Ra value is roughly 5 times for LS in SR2 than in SR1 for all the three positions. This decline may be due to higher application of pressure and increased chattering at higher depths of cut in a bid to remove the milling feed marks and establish a new layer. However it is seen in Table III that Ra value for LS is still better than that obtained through HS or through AS. In SR2 as the number of passes is high the feed marks of the parent process (milling) are entirely removed and a new surface topography consisting of feed marks made by the scraping tool only is generated. It is observed that this causes the Rq value and the other parameters to increase in Fig. 3 HS Process graph. comparison to SR . 1 As seen in Fig. 4 for SR , the surface consists of many It is evident from the Table II that the finish provided by 2 plateaus at a significantly higher departure from the mean line AS is the worst. Although the AS configuration has an when compared to the surface topography in SR . These oscillatory output just like the LS configuration, the tool used 1 plateaus could be formed by the scraping tool during the LS therein is toothed that results in a poor finish. Besides this process. They may be a result of over scraping during which the cutting edge of the tool blade is along the arc generated by the tool stayed at one position for a longer duration. A surface the oscillatory movement which results in removal of material topography consisting of plateaus and valleys was thus in the form of a line. In such a case it becomes difficult for the resulted. This plateau region can cause the Rq value to user to get a reference while scraping. For LS, the tool used is increase significantly. Such plateaus which are predominant in a scraping tool bit whose cutting edge is perpendicular to the the SR graphs are infrequent in SR graphs as seen in the feed direction due to which it removes material to form a 2 1 Fig. 5. rectangular flat scraped surface. This enhances the control over the scraping process. Other disadvantage of the AS tool is that it is flexible in nature. When the operator tries to remove extra material by exerting pressure, the tool bends compromising the pressure and changing the cutting angle. Even in HS the cutting angle varies during the entire stroke since it is hand controlled. This variation in cutting angle is inversely proportional to the operator skill. For LS, since the entire assembly is rigid, a constant cutting angle is maintained throughout the stroke irrespective of the operator skill and in spite of change in the applied pressure by the operator. This may be one of the Fig. 4 SR2 - LS Process graph reasons that enhance the surface finish. In SR1, the surface is composed of peaks and valleys generated by milling and scraping both. The metal removal process could have taken place in two ways. Firstly if any peaks of greater height (generated by milling) came in contact with the scraping tool, they were shaved off part by part in each pass leaving peaks of lower height untouched. Secondly the scraping tool could have cut off the entire profile in one pass and establishes a new profile on its own depending on its interaction with the surface. However if we divide the volume of material removed as calculated in Table IV with the area Fig. 5 SR1 - LS Process graph scraped, we obtain the total depth of material removed. This C. Material Removal Rate total depth when divided with the number of effective passes yield the depth of cut for each pass. This value of depth of cut Table IV and Table V show the material removal rates for is comparable to the peak heights or valley depths. On may SR1 and SR2 respectively wherein “M/C” denotes the type of conclude that the material removal occurs in the form of machining. The material removal rate in SR1 for LS is about 5 severing of peaks as specified in the first method. times than that of HS. This is mainly because LS has higher number of SPM which results in faster removal of material. B. Comparing Parameters of the surface created by SR2 Besides this scraping for LS takes place in both the directions

The Table III shows the parameters obtained after SR2. The - forward and backward unlike hand scraping where the

168 International Conference on Mechanical, Automobile and Robotics Engineering (ICMAR'2012) December 14-15, 2012 Singapore backward stroke is unproductive. The disadvantage associated protrude above the core roughness region Similarly the with LS is its smaller stroke length. HS Stroke length is about average Rvk/Rk value is higher for LS graphs than for HS 90 times that of the LS Stroke length. However this is graphs for both the rounds of scraping - SR1 and SR2. One compensated by the higher oscillations per minute in LS. may conclude that LS generates more valleys that project In SR2 the material removal rate has increased for each through the roughness core profile than HS. Since scraping is performed majority of times on mating process. This is because the objective of SR2 was to eliminate the feed marks and establish a new surface due to which a surfaces which involve interaction or transfer of forces, a higher depth of cut was taken. The material removal rates surface with lesser Rpk/Rk value is preferred [11]. Same holds were calculated so as to compare the material removal true for dynamic loading. This is because over a period of capacity of the three processes under the similar conditions. time the peaks in a surface wear off due to the interaction Thus the ratios of the material removal rates become more between the mating surfaces. It is thus preferred to have lesser significant than their absolute values. number of wear susceptible regions in a surface. Also lesser the number of peaks more is the contact area available for D. Comparing Bearing Ratios of LS and HS force transfer and more uniform is its nature. A smaller value Bearing Ratios and Abbott Curves can help in further of Rpk/Rk indicates that the peaks occupy lesser area analysis of graphs representing the surface profile [9]. Since compared to the core roughness area. AS does not qualify in attaining the primary objective of The Rvk/Rk values observed in Table VI are higher for the providing satisfactory surface finish, its surface graphs were LS process than that produced by the HS process. This is a not considered for bearing ratio calculations. Table VI gives favorable situation since valleys occupy the debris of peaks us the Bearing Ratio values for both the rounds of scraping for eroded by wear and prevent them from coming in contact with the LS configuration and the HS. The values are calculated for the interacting surfaces [11]. They also act as the reservoirs the depths of 20%, 40%, 60% and 80% of the entire range for holding lubrication oil which assists in reducing friction each graph. Abbott curves were plotted as shown in Fig. 6 and between surfaces in relative motion. The percentage of area the ratios of Rpk as to Rk and Rvk as to Rk were calculated occupied by valleys out of the total area in a surface profile is for each position of sampling [10]. Rk is the depth of the core compared and shown graphically for the LS and the HS in the roughness profile, Rpk is the average height of peaks Fig. 7. The figure supports the trend shown by Rvk/Rk values. protruding above the core roughness profile and Rvk is the It is also observed that the area occupied by valleys increase average depth of valleys projecting through roughness core for both the LS and the HS processes from SR1 to SR2 profile. The average values of the ratios are stated in Table VI. because of the decrease in the core roughness region (Rk value) calculated from the Abbott Curve. This decrease is because of the higher depth of cut taken in SR2 that resulted in a more fluctuating profile contributing to increased values of surface finish parameters like Ra and Rq.

Fig. 7 Comparison of Valleys produced by LS and HS

Processes that tend to produce surfaces with lesser peaks protruding above the core roughness are preferred. Besides this, larger smooth regions that reduce friction so as to provide more running clearance are required. Valleys for effective lubrication are also desirable. A surface having all the above Fig. 6 Sample Abbott curve for the corresponding LS profile showing Rpk, Rk and Rvk values. mentioned qualities is produced by LS and is thus superior than the one produced by HS. It is seen in Table VI that the average Rpk/Rk value for LS is lower than that of HS in SR1. This trend continues in SR2 also. It is safe to say that LS produces lesser peaks that

169 International Conference on Mechanical, Automobile and Robotics Engineering (ICMAR'2012) December 14-15, 2012 Singapore

V. ERGONOMICS shown that the effectiveness of scraping depends on the parent process also. However even at higher depths of cut, LS A. Direction of Scraping performed exceedingly well and provided surfaces that were Hand scraping is a time consuming and a tedious operation. consistent and suitable for load bearing applications. The hand It was hence decided to incorporate ergonomic factors in the controlled feed mechanism makes the LS configuration machine to make it easy and convenient for handling for the portable and universal for use just like hand scraping and user. As stated before the LS configuration removes material reduces operator discomfort. It is a successful step towards the in the same direction as that of the oscillations unlike AS. This automation of scraping process and further research will be is shown in Fig. 1. This allows better visibility of the part done in future to reduce the involvement of human effort and being scraped. Besides LS removes material in the form of a skill in scraping. rectangular plane unlike AS which removes material in the form of ridges. Thus LS gives better reference with respect to ACKNOWLEDGMENT the depth of cut and the area scraped than that provided by We would like to thank Larsen & Toubro (L&T), Talegaon AS. MIDC, India for guiding the Scraping Machine Development B. Angle of Scraping project and the Polymer and Advanced Material Laboratory (PAM), National Chemical Laboratory (N.C.L), Pune, India for their support.

REFERENCES [1] R. R. Wade, The Art of Hand Scraping, Lawrence Livermore Laboratory, 29 April 1981, pp. 1–34. [2] P. Wenghöfer, Scraping of Plane Surfaces - Course: Technique for Manual Working of Materials. Methodological Guide for Instructors, 1st ed., Berlin: IBE. Fig. 8 Positions of LS for Scraping (schematic). [3] T. Atkins, The Science and Engineering of Cutting. The Mechanics and Processes of Separating, Scratching and Puncturing Biomaterials, Metals and Non Metals, Butterworth Heinemann, 2009, ch. 4. In practice the hand scraper is held at an angle of 30 to 40 [4] H. Yukeng, C. Darong and Z. Linqing, “Effect of surface topography of degrees with the surface. The operator tends to hold the scraped guideways on their tribological behavior ” machine tool also at an angle which results in change of Tribology International, vol. 18 Issue 2, April 1985, pp. 125–129. [5] K. C. Fan, J. Torng, W. Jywe, R. C. Chou and J. K. Ye “3D cutting angle as shown in Fig. 8. In position (a), the machine Measurement and Evaluation of Surface Texture Produced by Scraping is held horizontal to the surface due to which the cutting angle Process” Elsevier Measurement, vol. 45 Issue 3, April 2012, pp. 384– of 40 degrees is maintained. In the position (b), it is inclined 392. [6] T. H. Hsieh, W. Y. Jywe, H. L. Huang and S. L. Chen “Development of by 30 degrees as per the operator’s habit. As a result the a laser-based measurement system for evaluation of the scraping effective cutting angle changes to 70 degrees. In the position workpiece quality” Elsevier Optics and Lasers in Engineering, vol. 49 (c), the tool holder link attached to the machine shaft is given Issue 8, August 2011, pp. 1045-1053. [7] Y. Takeuchia, M. Sakamotob, T. Sata, “Automation of Scraping Works an angle of 30 degrees to compensate for the inclined holding. by a Robot Equipped with a CCD Line Sensor and a Contact Detector” As a result although the machine handle is inclined by 30 CIRP Annals-Manufacturing Technology, vol. 37 Issue 1, 1988, pp. 489- degrees the cutting angle still remains 40 degrees. This helps 492. [8] L. D. Chiffre, P. Lonardo, H. Trumpold, D. A. Lucca, G. Goch, C. the operator to hold and position the machine just like his Brown, et al, “Quantitative Characterisation of Surface Structure,” usual method of holding the hand scraper thereby increasing CIRP Annals-Manufacturing Technology, vol. 49 Issue 2, 2000, pp. 635- the scraping efficiency. 642, 644-652 [9] M. Rîpă, L. Tomescu, M. Hapenciuc and I. Crudu, “Tribological Chareacterisation of Surface Topography using Abbott Firestone Curve” VI. CONCLUSION in National Tribology Conference, Galati, 2003, pp. 208–212. The performance of the linear scraping configuration was [10] Z. Lipa, D. Tomaníčková, “Choosing The Most Appropriate Mathematical Model To Approximate The Abbott Curve” Materials compared with the widely available angular scraping Science Technology, vol. 10 Issue 4, 2010, pp. 37-43. technique and the conventional hand scraping method under [11] N. Allard, Consequences of Machining on Roughness and Functions of same conditions. Two scraping regimes are discussed - the Cylinder Liner Surfaces, University of Halmstad, June 2007, pp. 1-31. first regime has lower number of passes that resulted in severing of peaks and the second regime had higher number of passes that resulted in creation of a new surface topography. The advantages of LS in achieving a surface having a better finish and a better utility for load bearing surfaces were established. However since the vertical feed is hand controlled for all the three types of scraping, it is observed that the surface finish quality declines when the depth of cut is high or if the material is over scraped. It is thus

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