I have my first boring job to undertake. I need to bore a 0.787" hole 1.75" deep in 1.25" diameter 1045 steel bar. I'm using a CG5 CPHB21205 insert in a Circle/Widia 3/8" carbide bar. I'm trying to figure the SFM to deduce the RPM needed. I'm looking at the Widia/Circle catalog (here) and I don't understand the speed and feed chart found on page 62. What's the "ap [inch]" or "f [inch]" column mean? I've looked all over the catalog but can't find what that is. Is that a hardness rating of the work? If I knew what that was I think the rest would hopefully fall into place. Really appreciate help here. Thanks.