How to cut derailleur cable housing
I see you don't want to buy the proper tool - do consider that while some are silly expensive, there are also reasonably priced alternatives.  Brands like Birzman and X-Tools are a third the cost of a Park or Pedro's tool.

Another option is to use a rotary cutoff disk in a tool like a dremel, or even a full-sized cutoff wheel in a grinder.   If you have one already, then this is a no-cost.  To buy one would cost more than the right cable cutter tool as already suggested.