PolarPlot[Sin[3 t], {t, 0, Pi}, PolarAxes -> Automatic, PolarAxesOrigin -> Automatic, PolarTicks -> {"Degrees", None}] AddYou can add the option PlotRangeClipping -> FalsePlotRangeClipping -> False:
PolarPlot[Sin[3 t], {t, 0, Pi}, PolarAxes -> Automatic, PolarAxesOrigin -> Automatic, PolarTicks -> {"Degrees", None}, PlotRangeClipping -> False] 
