That is a 1/3 HP, 1725 RPM motor that I'm using. A smaller motor would probably be sufficient, 1/6 or even 1/8 HP. Pulleys reduce the speed of the filer to about 850 RPM.

Die Filer
I made this die filer from a kit purchased from Andy Lofquist owner of Metal Lathe Accessories (MLA) Box 88, Pine Grove Mills, PA 16868 Phone: 814-234-3543

I'm not affiliated with him in anyway...just pleased with his kits and with him. His kit prices are very reasonable
It has proved to be an invaluable tool for my type of machine shop work, which is currently the building of model engines. I highly reccommend a die filing machine of some sort for this type of work. A lot of small parts may only have a surface or two that are machined but they must be cleaned up and made to look good, appearance to me is important and the die filer is a quick and easy way to get there. Precision surfaces can also be created, I don't mean that the die filer is only for making pretty.
The primary parts are cast iron with bronze sleeves for the two drill rod shafts. The sliding yoke arrangement runs in a bath of oil providing a very smooth quiet operation.
It is designed to be completely made on a 9" lathe although availability of a milling machine makes it a little easier. A drill press is necessary also.
One of the nice things about this MLA Die Filer is that Andy provides instructions on making your own files. Essentially you purchase off the shelf conventional files and make a 1/4" dia. x 1" long adapter shank that you insert a ground down shank of the file into. A little JB Weld holds it all together. Total length of the resultant file is about 3 1/4" so you can frequently get two die filer files out of each 8" or longer file that you purchase. I've made up a batch of rounds, square, triangular and flat files of different cuts.
Following are photos of my Die Filer.