John, there was a hole for the shaft that was about 4-5” deep. The insert actually had a smaller shank than the ones you make. I had a fairly large bulb on the handle into which the insert was fitted. The catch was a moment of inattentiveness. I had a bowl that was being turned and when I was looking away from the work I let my gouge contact the wood. The tool was probably 2-3” off the rest. Valuable learning lesson on paying attention.
Like you, I have folks that visit often and I would be afraid to let them use any tool in a wood handle unless it had a ferrule. To be clear, there are no lathe tools in my shop without ferrules. In fact, probably 3/4 of my tools are in D-way handles.