Doc grid setup

I am doing the design a 9ft table and I'm having trouble with the doc grid.

I am trying to do a drawing with an accuracy of 1/16" want all my objects to snap to this 1/16" limit.  I have put the scale to 1:16 so that my drawing will fit on one page and I have put 16 grid lines per inch, yet the highest accuracy I can obtain is 1/8". 

Thanks,

Gaetan