replying to Christopher Tidy, Manish chandra wrote:
Hi ! this is Manish , like see i also had the same problem too which you are
having , so i tried in many ways one you can do is use* acid* but that may be
very dangerous , so instead *you can use the fire up technique* in which you
can heat up the blunt blade to a very hingh temperature and then rub it
against a hard plain surface which will make it sharpen (*/_THIS IS ONLY FOR
ADULTS KIDS DO NOT TRY THIS_/* !!!)
Regards
Manish.

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for full context, visit https://www.polytechforum.com/metalw...ade-77476-.htm

I've found, in most cases, that the apparent dullnes is caused by a
build up of adhesive along the cutting edge. This can usually be
removed with a petrolium base solvent. Another approach would be to
touch up the cutting edge by deepening the notches in the metal
cutting strip with a fine sharp cornered needle file or a dremel
cutting wheel.