if expense isn t the issue carbide is the best , , if you use a steel bar snug it up , +.1 on the overall length to reduce chances of chatter , even if you have to sharpen the insert tip do it , i know that idea will make a lot of guys cringe , but use it as a last resort , i really don t think you will have any problem if you use a carbide bar , keep the feed and speed to the sfm recommended by the manufacurer , i recently worked on a lage piece with a bore size of 1.5" +-.0002 , it ran like crap i had to grind the boring bar ( solid bar no insert ) a couple of times till i found that sweet spot , it cut beautifully , i know i ran it at 160 rpm but i think 1 in/min and lots of cutting oil , no coolant |