I have 3 die filers. The Butterfly is the one I use the most,as it is quick to set up. I STRONGLY URGE you to put a variable speed motor on yours,like I did. 1/2 H.P. is more than enough.
All these die filers run WAYYYYY too fast,which wears out the files very quickly. Also,the fast speed snaps small parts down on your finger tips. We had some women in my wife's jewelry shop,who needed to use the die filer,but after a few finger snaps were afraid of it. SOOOOO much more pleasant and controllable with a variable speed motor running MUCH slower. You can find cheap
speed controllers on Surplus Sales. Or,go to the PENN STATE catalog and they sell a small 1/2 H.P. mini lathe motor with controller for $115.00. It is powerful enough for this job,and pretty cheap.
The files are too expensive to be wearing them out. For the most part,before I got a bunch of die filer files,I have used a COARSE 6" half round Nicholson file. Grind the tang off. I don't want to ever get poked in the eye!! I ground the edges down some,too,so the front end of the file would go into the chuck. This file works very well for most work,and can be turned around to use the round side. Slowing the file down has greatly increased the file's life.