60 or 40 degree bit?

To cut the Rowmark's ADA applique sign material, they recommend a".005 FLX (flexible) Carbide tipped bit w/ flat/tapered shaft." I found these on Ebay but the manufacturer says most people use a "40 degree" bit. Which degree do you use? Thanks ebaydotcom/itm/271366609906

Wayne

there is a good bit of info here though it deals with engraving machines rather than cnc machines. http://www.antaresinc.net/EngSTD.html

Thanks Mike!