Bicycle Mechanics - what can i use to hack an ACS freewheel tool?

I want to ream out the inside of my ACS freewheel tool so that I can use it to remove an ENO hub, thus saving about $40.

I have this something that looks like this:
http://www.kovachiwheels.com/media/catalog/product/cache/1/image/5e06319eda06f020e43594a9c230972d/a/c/acs_freewheel_spanner.jpg

I need to remove some metal from the inside to make something like this:
http://www.wheelbuilder.com/store/white-industries-eno-freewheel-tool.html


I have drills, grinders, etc.

Or, cheaper to by the right tool and not hack mine?

The tool is $40 shipped. I have neither the expertise, the tools or the time to modify such a thing.

Freewheel tools are extremely tough steel. If you do this at all it will be with a die grinder and abrasive stone toolbits. Anything else will just ruin the steel of the tool you're trying to do the cutting with.

I suppose a Dremel tool and few grinding bits and plenty of time would do it. Keep the metal cool by dipping it in water periodically to avoid damaging the temper. Me? I'd spend the $40.

May be cheaper to give an LBS $5 to remove the freewheel for you.

two out of four is not bad.

Just remove the eccentric unit from the axle and then you can use your tool without modifying it. It is held in place by a small allen bolt. Once you remove the bolt holding the eccentric on you can use channel locks or something to wiggle the unit off of the hub shell. Also, you might want to consider getting a White Industries freewheel for replacement - they really do last much longer than even Shimano freewheels.

A punch/flat screwdriver and a hammer can do miracles also.

I'd modify it on vertical drill, and moving the table to create the eccentric. But it may be not needed as hockeyteeth suggests.