I did not use Acme rob,
but I think you can buy a tap,
I use 1/2 X 13 all thread,
Just placed by block in the drill press and after making "pilot" Hole
I hand turned the tap all the way through.
I found the best price on Bar Stock from
http://www1.mscdirect.com/CGI/INSRHI?PMSECT=1930
Shipping was high though... ( almost the same as my small piece of 1" X 1" X 12" )
well hope it helps.