I agree with the others. are you talking about a cassette or a freewheel? we need pics
I don't see anything in your original post to indicate a chainwhip or other tool is being used to hold the cogs. I never heard of putting a cassette tool in a vice like a freewheel tool.
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk