Chuck,
Just saying "TCMT insert" does not tell the whole story -- we need a size. The Enco, MSC, or other major industrial supply catalog will have a table of insert values that will list some of the clamp screw sizes for various inserts. I find it easier to look up a holder for the insert as they will have a "replacement clamp screw" reference that should tell you what you need to know. The thing to remember is that most of the "new" (call it post-1990) inserts are based on metric screws which means that the countersink angle is 90° rather than 82° and that getting this right is critical to proper operation. (You really do not want to know how I "learned" this.) Be sure to buy the strongest grade of screw you can as these puppies take a lot of load.