Pinch nut on tensioner pulley
 

I have rounded off, and generally messed up, the nut on the axle bolt in the middle of the tensioner pulley, on my 2007 Maxima. I know the nut takes a 14mm wrench, but how do I describe the bolt size and thread pattern to the hardware/parts store, so I can have a replacement nut when I can finally coax the original nut off. I'm hoping a cold chisel, small hammer, and possibly a micro torch will help me get out of the mess I created with vice grips. Thanks for any advice.

Why not use vice grips? If I'm reading it right, take the nut to a Home Depot/Lowes and find the same nut in the hardware aisle.

use a rounded bolt remover on an impact wrench, craftsman and mastercraft make those, I got a set for cheap.
will grab and remove bolt.

and don't try to remove stuck bolts with a vice grip...

Yeah, I learned from this experience not to use vice grips on stubborn nuts. There is barely 1 1/2" clearance between the tensioner pulley and the frame, so an impact is out of the question. I have a plan to use a short blast with a micro torch, and then tap the edge of the flange on the nut with a small hammer and a center punch. I'm just hoping someone can tell me the size, and the thread pattern of the nut, that I have messed up, so I can have another one ready to replace it with when I do get it to loosen and come off. I was trying to help my son replace the serpentine belts on his car the last time he was in town, when I screwed up this nut. He'll be coming back thru town next week, overnight, and I'd like to have the correct size nut on hand to try and fix the problem I created the first time.

honestly, no clue....

Just order a brand new pulley assy part# 11944-8J10B (double check with your dealer against car VIN). Stop messing with rounded off nut and your son will thank you. And use appropriate size wrench next time, when dealing with hard-to access fasteners, never use vice grips. Preferably gear wrench on this particular nut due to limited space. From what I remember, it is easier to access from wheel well, from the bottom.