Your double-sided DTB series inserts are very thick, providing outstanding strength and superior tool life in operation. With this increased thickness comes the requirement that the feed per tooth (FPT) not exceed the clearance the insert allows.
In general, it is recommended to initially not exceed an FPT of .025". Under certain circumstances (lighter DOC and/or WOC) the feed can be higher, but the potential for rubbing (or heeling) of the back-side cutting edge exists. When trying heavier feeds, evaluate the back-side cutting edge after running the tool for only a few minutes, looking for evidence of rubbing or damage.
Your DTB series inserts utilize chip-thinning for optimum performance. Chip-thinning is the process in which the actual chip thickness created by a cut is less than the FPT at which the tool is programmed. See the chart below to see the chip-thinning factor for various depths of cut. For a correct chip thickness, multiply the FPT (from the recommended cutting speeds chart PDF) by the chip thinning factor below. This will give you an accurate feed and optimize your performance.
This diagram shows the varying chip thickness when feeding .010" feed per tooth (FPT) at different depths of cut (DOC) with a 12mm diameter insert: At .250" DOC, the chip thickness is a true .010" At .100" DOC, the chip thickness is .008" At .060" DOC, the chip thickness is .006" At .020" DOC, the chip thickness is only .004".