Turning and boring tapers . Derry CoUard Co Figure 11. A common method of graduation. If the graduation is as indicated in figure 12, youcan only measure 45 degrees in either direction or 90degrees in all. By increasing this to 60 degrees andputting additional marks at 30 degrees each side ofthese, 180 degrees can be obtained as with the first II Turning and Boring i apers. g-raduation shown. But in any case, if you rememberthat it is the number of degrees out of center oraway from normal position that counts, there will beno trouble. Now, if we move the compound rest out of center15 degrees,
Turning and boring tapers . Derry CoUard Co Figure 11. A common method of graduation. If the graduation is as indicated in figure 12, youcan only measure 45 degrees in either direction or 90degrees in all. By increasing this to 60 degrees andputting additional marks at 30 degrees each side ofthese, 180 degrees can be obtained as with the first II Turning and Boring i apers. g-raduation shown. But in any case, if you rememberthat it is the number of degrees out of center oraway from normal position that counts, there will beno trouble. Now, if we move the compound rest out of center15 degrees, as shown in figure 13, we shall make a cutwhich is 15 degrees away from the square facing-offmovement of carriage, 75 degrees from the center lineand 150 degrees of included angle, as shown. This iswhat fools many a man who is not used to angles or acompound rest, for having moved the rest 15 degrees,he never thinks but that he will get a 15 degree Deny CoUai il Co Figure 12. Another method He will if he measures from across the end, but in noother way. This shows the necessity for having draw-ings plainly marked, so as to show whether the anglegiven is the total or included angle or the angle be-tween the center line and the side. The total or in-cluded angle is the one generally meant, and will beconsidered. 12 Turning and Boring Tapers. There is too little care used in expressing anglesof globe and other valve seats. A 60 degree seat iscommon and means 60 degrees total angle, as it should,but in the next breath we speak of a 45 degree seat,when it should be a 90 degree seat instead. Setting the compound rest to 30 degrees and wehave a total angle of 120 degrees, while if it goes to 45degrees, it gives a total angle of 90 degrees.
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