My dearly departed Dad left us a spool of .080 the size of a battleship gun round, so this should last us our lifetimes! LOL. Our pootie little Ryobi 18V weed-eater bit the dust, so we got a 2nd hand 40V Black & Decker that cautioned "only use .065 line".
Well, our donor also gave us pre-wound spools of that size, but I could not rewind the empty ones with the thicker plastic line, so I awl-ed out the keeper hole and slot to accept it. Tried it and it works absolutely fine! I did Dremel sharpen the cutter blade on the housing after a nice scraper cleaning.
BTW & fyi, those pre-wound spools are kept in place with reinforced packing tape, so it takes longer to remove that mess than to simply wind your own, like I did from dear ol' Dad's "barrel-O-trimmerline"! Hope that helps Y'all.
The reason we all need a clean and sharp cutoff blade on the housing is because otherwise it will "gum" the line, and sling out more of it until inertial forces pull wasteful amount of material out of your magazine. Sorta like eating corn on the cob with no teeth. Apologies in advance for being a nerd & an engineer.
