1545102$291771921756868428387 n

3ó

Choprer 1

Cutting edge

cos 8 = 1 -    (1.24)

d,

wherc d, is the diameter of thc cutter and a, is thc woriring engagement (the instantaneous engagement of the tooi with the woricpiecc), mcasured in the piane containing the directions of priraary and feed pnotion and per* pendicular to the direction of feed motion. In slab milling the working engagement was lenown as depth of cul

Now    —

Machinę Tools o od MoOtr.ing Operonccs

07

(1.25)

and subsutudon of (125) in (123) givcs

(126)

Finally, if ajd, is smali.

(127)

When esdmaung thc machining dme t_m in a milling operadon, it should be remembered that the distance traveled by the cutter will be largcr than the length of the woricpiece. This extended distance is illus* trated ir. Fig. 129 in which it can be scen that the cutter travel distance is given by ^ -r \/a ,(d, — a,) where l_w is thc length of the woricpiece. Thus the machining dme is givea by

(128)

_ -f y!aXd, - a_f)

The metal removal ratę Z» will be equal to thc product of the feed speed and thc cross-sccdonal area of the metal removed, mcasured in the direcdon of feed modon. Thus, sińce the back engagement c. is eąual to the workpiece width.

£r

7

Figurę 129 Rc!adve motion oecween a slab-milling cutter and the woricpiece during machining dme.