Best way to enlarge a DXF drawing for cutting tool paths?

Hi All:
Regarding cutting wooden parts on a HobbyCNC 3 axis mill:

What is the best way to enlarge a part on a DXF file to compensate for
the tool width? I have parts for an airplane I wish to cut. In ModelCAD
(or any other drawing program) if I select the part and use the "scale"
option, and I scale the selected part by 1/2 the bit size (i.e.: I scale
the part up 0.015625 -- 1/2 of the 1/32 inch cutting tool--), I get an
uneven result. The length and width scaled do not even come close to the
0.015625 outline I am trying to achieve. All I want to do is get a
0.015625 outline of the part I am wanting to cut, and put that outline
on a different layer so as to use that layer for the tool path.

Any suggestions? What do you all do to compensate for the tool size?

Thanks for helping a newbie!

Mark