When used as a verb the difference between shear and sheer often leads to confusion because of similar, but different meanings. However, the adjective "sheer" means “nothing other than,” “unmitigated,” or “of very thin or transparent texture.” A less common use of "sheer" as a noun would mean a sudden change in direction or straight up or down as in a "sheer cliff". The noun "shear" refers to the act or process of cutting or slicing. The terms "shear cut" and "shear scrape" are noun phrases. Not that Lyle will agree, but you are correct.
The simple way to remember which is correct would be if whatever you are talking about has anything to do with slicing or cutting then the correct word to use is "shear" (sheep shearing, wind shear, metal shears, shear scraping, etc). Otherwise, "sheer" is usually the right word (sheer luck, sheer cliff, etc).