"Fred Holder" wrote: (clip) I generally drilled two intersecting holes in
the end of the shaft one on the center line of the shaft and one at 45
degrees.(clip)
^^^^^^^^^^^^^^^^^
You can also drill holes at both ends of the shaft, doubling the number of
choices on diameter and angle.

People have discussed the difference between hot and col rolled mostly in
terms of manufacture. In terms of use: cold rolled is smooth and
shiny--hot rolled is dark and scaly. This could make a tiny difference in
how the tool slides aross the tool rest. Hot rolled is cheaper. Cold
rolled is a little stronger because the rolling work-hardens it. All these
differences are trivial for your application. Buy whichever one you find
first.