This is quite an old thread but I’ve only just happened upon it. There doesn’t seem to have been a conclusion so I though I’d relate my own trials.
I bought a torque driver that claims a range from 5 to 60cNm (0.05 - 0.6Nm) and even came with a calibration certificate for the points at 60, 36 and 12 cNm.
My usual cartridge is an Ortofon SPU Royal N which comes with its own screwdriver and peg wrench. Using either of these against the torque driver I couldn’t even get to 5cNm, more like somewhere between 2 and 3. Assuming Ortofon know their cartridge’s robustness I forbore to apply a grip stronger than fingers and just used what I could achieve comfortably.
I’m using a Schröder Reference arm and a brass cartridge mounting plate, the plate attaches to the wooden “head shell” of the arm with a single screw and here the tightness really matters. Too tight and though the music has a swing to it the dynamics are subdued and there’s no excitement, to get this cartridge to play rock music convincingly requires this screw and also the counterweight grub screw, which dears on a plastic sleve, to be barely tight enough to hold their positions. A bit of Dio era Black Sabbath happened to be at hand when setting this and was quite telling. The angle of an allan key and listening was the only way to gauge these in the end, the torque driver was well below its useful range.
Where the torque driver does come in handy is the screw that locks the arm height adjustment. The actual adjustment is by a hidden screw inside the pillar with a left hand thread but the setting is locked by another grud screw and 21cNm was about there and at least I’ve removed any inconsistency from this when adjusting arm height but it’s effect is quite marginal compared to the two key screws who’s torque I still can’t measure.
The Dynavector 17D3 I used while my SPU was rebuilt seemed to want a tighter setting on the mounting plate to arm screw but this was pre torque driver and just my impression. Probably every combination will be different.