axis tick lines do not display, keep tick labels


I am trying to plot X axis with major ticks set at the beginning of the month and minor ticks set on day 15th of the month. I'd like to have tick lines and no tick labels for the major axis, and tick labels but no tick lines for minor axis.

Could somebody let me know what I am doing wrong?

Thank You

Code Snippet:
       # X axis major
       day1 = MonthLocator(range(1,13),bymonthday=1,interval=1) # every month day 1
        # X axis Minor
        months = MonthLocator(range(1,13),bymonthday=15, interval=1) # every month on day 15
        monthsFmt = DateFormatter('%b')

        # X No tick lines
        for t in ax.xaxis.get_minor_ticks():