I have found my TIn Lizzie 18LS to NOT be fussy about thread. I have only found one brand of thread that it didn't like and it often broke. I regularly use Isacord 40 wt. polyestor, Coats and Clark 40 wt. cotton, Star 40 wt. cotton, Signature Pixelles 40 wt cotton, Coats and Clarks polyestor, and Connecting Threads 50 wt. cotton. These threads all work fine in my Tin Lizzie 18LS.