RECOMMENDED LATHE PRACT~CE-{c(H'd(L) r==J I INS. TAPER ~ PER FT. _ ! or I ... MM TAPER. PER METRE. ~ F!G.1 The recommended cutting speeds for reaming are: Cast iron 20 ft. per min. Mild steel 35 " " Medium carbon steel Phosphor-bronze Aluminium and duralurnin FIG. 3 (6 m) (ro·6 m) (9 m) (10'6 m) (ro·6 m) 3 0 " " 35 " " 35 " " Methods of Taper Turning ami Boring. Three general methods are applicable. (x) As shown in fig. I, by means of swivelling the compound rest to the angle required for either boring or turning. This method is by hand traverse of the tool, and is limited to the length of movement of the top slide, but it has the advantage that taper surfaces of any angle can be machined.
~ r-- --l --_I n I ~ ----==~ ~:JEtt (2) The method shown in fig. 2 is by off-setting the tailstock centr~. The drawback is that the centre points are not on the axis of the work, so that the centres are subjected to uneven wear and strain. Thus the method is limited to slow tapers on long work. To find the amount of off-set X, if the taper is T inches per foot on FIG. 2 -~ 17