All good advice, even if most of is "Ooh you don't want to do it like that"
If you do want to do it like that:
The end of the S7 spindle is machined on the external surface:
Make a close fitting collar that can be fastened to the end of the spindle with a couple of grub screws with brass pads to protect the spindle end
Thread this collar for a suitable length of studding locked at the required depth with a nut
(the collar shown in the photo is actually for my depth stop which only works as a chuck depth stop and is adjusted from this end so the hole is plain. The depth is adjusted by the 40tpi thread in the 2MT blank. The collar stops it from flopping about – see below)
HTH,
Rod