I build HO resin models of freight cars which usually require drilling quite a few small holes for grab irons and detail parts.  For years I've used pin vises.  Lately, I've been using a power drill built from a Tamiya kit that Fred at Caboose Hobbies in Denver told me about a month or so ago.  

 

The Tamiya kit 74041 builds into a small, light motorized drill --- looks like a cross between a miniature power drill and a pistol ---  for about $25.  The drill is powered by 2 AA batteries.  Daren, a very helpful gentleman at Colpar Hobbies in Aurora, CO, sold me the drill kit and recommended a few changes.

 

I didn't have any trouble building the kit once I figured out how to interpret the pictorial instructions.  Construction took me about an hour.

 

The stock kit has two collets that will hold many of the size drills used in model railroading. The smallest drill my kit would hold is #66 using the smaller of the two collets provided.  I wanted to drill #80 holes.  Fred and Daren both told me a Dremel 483 collet would drop in place to hold tiny drills.  Daren also recommended replacing the main spindle bearing in the kit with a $3 drop-in ball bearing from a R/C car parts supplier (Traxxas part #4611 6x11x4mm).  I took his advice, but I'm not convinced the bearing replacement was necessary given the light loads and relatively slow speeds of the drill.

 

It seemed to me that just dropping the Dremel collet into the spindle nose resulted in too much wobble, so I made an adapter to fit within the Tamiya spindle and better center the Dremel collet.  (Turns out Fred and others have done the same, so this isn't an original idea of mine.)

 

Anyway, I've drilled a bunch of #80 holes with this thing and it works great.  I'm still a pin vise fan, but with this drill I tend to break fewer of the little drills.

 

I've attached a series of photos showing the Tamiya drill and the collet adapter.