Originally Posted by
Kenny Duval
Anytime you start stacking tool holding the tolernaces can go up. Say your R8 3/4 collet isn't perfect. Now add a TTS tool holder and now you have the already imperfect R8 collet plus whatever error is in the shaft and taper of the ER collet. Now add an inch of tool stick out. It doesn't take long before the TIR gets out of hand. .001 or .002 on a 1/2 cutter. No big deal. The cutter will wear a bit quicker and you make adjustments to deal with the oversize cutting. However put in and 1/16 cutter and you'll break them with regularity.
Even on my name brand TTS collets I took the time to measure and mark them so I could index them in the R8 collet to get the least amount of run out. Nothing is perfect.