There is probably a recommended torque rating out there but I try not to over tighten. It can suck the collet or arbor in tighter than it really needs to be, which just makes it difficult to remove. Bang-Bang removal is probably not great for the threads or the bearings. So tight enough so tool wont spin or loosen & just a teensy bit more. The way I stumbled onto this was occasional hand tightening & forgot to wrench obviously not paying attention. But I'm sure if it was heavier cutting I may not have gotten off as easy. My spindle is R8 so might be a bit different to MT. I use a Milwaukee cordless driver & socket on my drawbar, more as a reach convenience, but another plus is you can set the clutch torque & be somewhat consistent.