with the emergence of the needles 21 from the backing material the needle bar 11 can be shifted laterally to the left at any time prior to the needles 21 again entering the backing material the tufting machine 10 however is programmed by the cam 17 to accomplish the initial lateral shifting left or right as the case may be for that half cycle of the process during an initial part of each down stroke thus upon exiting as shown in fig1 the needles 21 continue their travel in their linear vertical paths to top dead center as shown in fig1 whence the needles 21 again begin their descent from the fig1 position to the fig1 position during this travel cam follower 15b passes into valley 27b as cam follower 15a ride on lobe 25b the effect being that the needle bar 11 is shifted left by one fourth the distance between axes of adjacent needles 21 and the needles 21 descend to their penetrating position as shown in fig1 while being so shifted after entry the progressive rotation of cam 17 removes the lobe from follower 15a and removes valley 27b from follower 15b thereby causing a right shift so as to return the needle 21 to their unshifted or normal or centerline position as depicted in fig1 the needles 21 continue their downward travel.