Learned a trick from an old book for removing threaded cogs from freewheels without tools.....break the chain and lay the upper run across any cog other than the smallest, and loop the lower run over the smallest cog from underneath, then try to pedal backwards...repeat as required to remove other threaded cogs. Tried this on an old Suntour freewheel and it worked fine, but you do need to be carefull as the cogs sometimes break loose suddenly. The book said this could also be done without breaking the chain, but have not tried that yet....