Originally Posted by
SCzEngrgGroup
Depends what you plan to do with it.... For an ATC, BT30 (or ANY real machine taper - BT/ISO/etc.) is preferable to R8. But, of course, your only choice for an off-the-shelf ATC is the Tormach one, which REQUIRES R8/TTS. For manual use, it doesn't make one bit of difference which you have, which one small exception - The Tormach PDB does not reliably retain TTS toolholders under maximum-effort cuts (MRR >= ~3.0). I dont know of Tormach has a version of their PDB that supports BT30, but if you plan to push the machine to its limits, and/or work with hard materials, AND use the Tormach PDB, I would get confirmation that the pullout problem does not exist with that combination. If you're not using a PDB, then, again, there is no reason to prefer one over the other. R8/TTS toolholders are generally cheaper, and more readily available, than BT30.
So, to answer your question as to which is better, R8 or BT30: It depends...
You absolutely can swap out the entire spindle cartridge to change from R8 to BT30. That has been an available option for many years, and it is a very simple swap.
Regards,
Ray L.