An analysis of the effectiveness of reaming as a secondary operation for hole production
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This investigation was concerned with the amount of accuracy and surface finish in the holemaking operation. Surface finish and accuracy were the dependent variables with speed, feed, tool diameter, and elapsed time being the independent variables. The secondary operation of reaming was also investigated to determine the increase in surface finish and accuracy versus the amount of machining time required to perform the reaming operation. In this study 1728 holes were drilled and an additional 1728 holes were pre-drilled then reamed under different drilling and reaming conditions. These operations were performed randomly. After drilling, then again after reaming, the amount of surface finish and the hole size were recorded. Also, the amount of tool wear after drilling and reaming was recorded. Some findings of this study showed that 1) in drilling operations: the main effect of feed was significant; a combination of the lowest feed and speed was not advantageous to other drilling combinations and any other drilling combinations were not advantageous to the combination of the highest speed and feed; with a decrease in hole diameter, an increase in feed resulted in undesirable holes, 2) with regard to surface finish: there was a significant interaction between feed and speed; the main effect of speed was significant with increasing hole diameter and insignificant with decreasing hole diameter, 3) with regard to dimensional accuracy: the main effect of speed was significant; an increase in speed caused a decrease in accuracy, 4) in small hole sizes better hole size and surface finish resulted from drilling rather than pre-drilling then reaming, 5) reaming improved the average surface finish and dimensional accuracy with larger diameters, 6) in increased hole sizes the percentage of improved accuracy and the standard deviation increased; the percentage of improved surface finish and the standard deviation decreased, 7) regardless of tool diameter, tool wear was insignificant; drilling speed has a significant effect on the surface finish and drilling feed has no significant effect on the dimensional accuracy of reamed holes, and 8) reaming feed has a significant effect on reamed holes.