Local hardware stores will carry small t-handle tap wrenches, usually made by General.
While you're at it, get a Micro-Mark truck tuner and a Kadee coupler gauge if you don't already have them.
It takes an iron man to play with a toy iron horse.
An alternative to the tool Micro Mark sells can be found at Harbor Freight Tools. They sell a 3-pack of tap wrenches that look similar to the one from MM. For $7 you get three sizes, the smaller one being the best for our trains. I have this set and the quality is fair but considering how infrequent I use it the tool will last me a long time.
http://www.harborfreight.com/3-piece-t-handle-tap-wrenches-38560.html
TONY
"If we never take the time, how can we ever have the time." - Merovingian (Matrix Reloaded)
The ones sold by Micro Mark are very good.
Too large a tap handle makes it easy to snap a tap. Something you don't want to do.
I have had the 2-56, 1-72, 0-80 and 00-90 for some years. Really needed with model train work.
To save time, one with the drill bit and one with the tap.
Most trains today come with Metric screws. Lose a screw, easy to do, and you have to tap with next larger SAE tap for SAE screw. Not aolways easy to find tiny Metric screws.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
Here's a non-ratcheting tap wrench for a little less money:
https://www.fastenal.com/products/details/0312222;jsessionid=1E6A3FE674A889A33054823252FA29D6.fcomjvm04?r=~|categoryl1:%22601071%20Cutting%20Tools%209and%20Metalworking%22|~%20~|categoryl2:%22601102%20Threading%20and%20Tapping%22|~%20~|categoryl3:%22601108%20Tap%20Wrenches%22|~
(Sorry, I can't make the link clickable. I tried the [url] stuff. Highlight the link and then right click on it. Select "Go to....).
I would suggest considering a non-ratcheting style for model railroad use. Tapping into white metal requires frequent reversal to clear the chips so having to flip the ratchet switch constantly could be a pain.
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
It's called either a tap wrench or tap holder. For small work you need something like this one sold by Micromark. http://www.micromark.com/ratchet-drive-tap-holder-6-32-max-capacity,6639.html
Joe
Oh Yeah,
I am in the process of fixing my rolling stock and doing a lot of truck repair/replacement and coupler conversion.
I need to buy one of these.....
http://i935.photobucket.com/albums/ad200/gmckenzie444cplmckenzie/taphan3sm_zps6joduozd.jpg
Anybody know what these are called so I search ebay and amazon for one.
cplmckenzie