Turning and boring tapers . 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 br
Turning and boring tapers . 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 Figure 13. Compound restmoved 15 degrees out of center Derry CoUard Co From this we can make a little rule to the effectthat the total angle of the piece turned will equal i8odegrees, minus twice the setting of the compound restfrom the square position, or subtract the desiredtotal angle from i8o degrees and ^ of the remainderis the correct setting of the compound rest. We wish to turn a valve seat reamer to 60 degreestotal angle, what is the correct setting of the compoundrest? Then 180—60=120, y^ of 120=60, which is thecorrect number of degrees out of center, for setting thecompound rest? Turning and Boring Tapers. A reamer is desired, having a total angle of 15degrees, what is correct setting of compound rest? Then 180 — 15=165, y^ of i65=:82%, or within 7>4degrees of being parallel with the lathe centers. Alittle thought wdll show this without the rule, as bytaking half the degrees in the total angle desired fromthe right angle position of the com_potind rest you getthe cor
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