Where would you find the terms 80 grit 100 grit and 120 grit?

terms used mostly on sand paper, emery cloth, or other fine abrasive material

You should always know the type of wood you are finishing before starting any sanding. The type of wood you are sanding has a direct relationship to the grit used for final sanding. There are two basic types of wood - softwoods and hardwoods.

Typical softwoods are Pine and Fir. Softwoods can be finish sanded with 150 or 180 grit prior to the application of primer. Please see Grit Guide for more information:

Grit Guide

Very Fine (220) For light sanding between stain and sealer. Fine (150-180) For final sanding or cleaning of wood surfaces. Medium (100-120) For moderate removal of surface imperfections. Course (60-80) For heavy removal of wood and coatings. * http://www.nortonconsumer.com/Data/Element/Node/Application/Application_edit.asp?ele_ch_id=A0000000000000001555"What are the grit sizes equivalent to?" United Kingdom:-

UF Ultra Fine:- approximately equivalent 420 Grit sandpaper.

F Fine:- approximately equivalent 320 Grit sandpaper.

M Medium:- approximately equivalent 220 Grit sandpaper.

C Coarse:- approximately equivalent 180 Grit sandpaper.

XC Extra Coarse:- approximately equivalent 120 Grit sandpaper.

XXC Extra, Extra Coarse:- approximately equivalent 80 Grit sandpaper USA:-

UF Ultra Fine:- approximately equivalent 140 Grit sandpaper.

F Fine:- approximately equivalent 120 Grit sandpaper.

M Medium:- approximately equivalent 100 Grit sandpaper.

C Coarse:- approximately equivalent 60 Grit sandpaper.

XC Extra Coarse:- approximately equivalent 46 Grit sandpaper.

XXC Extra, Extra Coarse:- approximately equivalent 24 Grit sandpaper * http://www.permagrit.com/faq.php