How well do the powerless sanding tools work on sanding the inside of bowls?

in my experience, the inertia sanders don't do well on typical boxes (inside) - the shape is not conducive to making the sandpaper turn

I prefer power sanding on bowls because I can control the speed of the sanding disk independent of the rpm and diameter of the bowl, and also because I can stop the bowl and work on problem areas by themselves. I use a 3/8" variable speed drill with the sanding disk held in a 6" drill bit extension. I turned a handgrip for the extension so I can hold that, not the drill - more comfortable and better control. I personally prefer slow speed sanding - less heat and the sandpaper works more efficiently and lasts longer - so I have been happier with drills that max out at around 1200 - 1300 rpm and usually sand at only a fraction of that. The lower gearing also means these drills have more power for equal amp ratings than higher speed drills for regular drilling and driving applications. If you want to try powerless sanding before investing, you can do it on the cheap by making your own handle without the bearings, drill a hole at an appropiate angle, add a drop of grease, insert your sanding disk, and have at it. Make sure the hole is shallow enough that the stem bottoms in the hole so the disk itself doesn't rub on the handle. I use one occasionally to reach deep inside something, and I don't even bother to turn the handle, I just use a square stick of wood ripped from 4 quarter lumber and cut to whatever length I want. These work so well that I suspect the fancy ones you can buy only have bearings so that they have something to sell, because there probably wouldn't be much market for a stick with a hole in it.

-mike paulson, fort collins, co

The handle is a piece of wood the length of the extension with a hole through it lengthwise. The drill bit extension goes through the hole which is a slightly loose fit and greased so the extension is free to rotate while I grip the handle. I turned a shape that fits my hand comfortably, and with a flare at each end so my hand can't accidently slip off.

-mike paulson, fort collins, co

I have experimented using your idea. It works and may be useful where you cannot reach with the 3/8 power drill.