Tormek T7 Setup - Grinding wheel either too tight or too loose

[ACoppersmith]

Hi all,

I've had a "mint in the box" Tormek T7 in my shed for many years, and am just now setting it up.  For installing the stone wheel, it came with a supplementary yellow instruction sheet which states to "mount the wheel with a 3/4" wrench... tighten the nut by hitting the wrench a few times with a hammer.  Do not tighten by pulling the wrench as there is then a risk of damaging the center of the drive wheel"

OK... that seems a bit weird using a hammer to avoid damage, but I followed these instructions to a tee.  Running the machine, the nut that holds the stone wheel kept unthreading itself and falling off.  So I tightened it a bit more... the wheel now ran slowly, then after a bit of tool grinding, would stop altogether.  The motor would hum but the wheel wouldn't move.  When I tried moving the stone wheel by hand, there seemed to be quite a bit of torque required to move it, much more than I expected. So I loosened the nut slightly and again, when I turned the machine back on, the wheel would start slowly spinning, but the nut would loosen itself and fall off.

I'm at a loss - can anyone help?  Anxious to get started sharpening my chisels and realize my investment in this machine!