Frogleg wrote:

...Nifty idea, but...if the OP wants this to dig smaller holes than a
bulb planter, how's he gonna get the dirt out?...



Sounds like a job for a soil sampler. It's a length of pipe, maybe 1"
diameter, with a section cut out of one side a couple of inches above
the bottom. T handle on top. One presses it into the ground and it takes
a core sample of the soil, which is then removed from the open section.
A small core remains below the open section, but it is easily pushed up
by the next sample.

You can buy one for $50, but I suspect that 1" EMT (thinwall electrical
conduit) would be ideal if you want to make your own. Maybe even 3/4".
Iron water pipe is sturdier, but more expensive, harder to work with,
and heavier to use. Copper tubing is more expensive and not as strong.
However, if you have something like that lying about, it would work. If
you have to buy something, try Home Depot or probably many hardware
stores. If you know an electrician he probably has leftover bits of
conduit. The $50 version is probably heavier duty, but for $50 you can
probably build 50 of them (not including labor).