The ornamental design for a helixadaptor for a pile, as shown and described.
FIG. 1 is a perspective view of a helix adaptor for a pile, according to our new design shown connected to an end of a pile in stippled lines;
FIG. 2 is a front elevation view of the helix adaptor for a pile of FIG. 1;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a left side elevation view thereof;
FIG. 5 is a right side elevation view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
Throughout the Figures, where shown the dotted lines showing additional structure of the helix adaptor for a pile or the environment are for illustrative purposes only and form no part of the claimed design.