When I see “how tos” that show people recycling t shirts into yarn by cutting with scissors, I cringe. It’s simply not possible to make any progress on bulk cutting with hand-powered scissors, no matter how wonderful your dressmaker shears may be for cutting out dress patterns.
I have a pair of Gingher dressmaker shears, and I keep them sharp enough to shave hair off my arm, and I love them. I use them for trimming, and releasing long chains of fabric, and sometimes for taking collars off polo shirts if I need to be extra careful around the buttons. I do not use them for turning the body of a t shirt into 50 yards of yarn.
(Some time ago, a girlfriend who knew that I make hand knit rugs from recycled t shirts came up to me and said, “How do you cut up t shirts? You can’t be using scissors!!” Indeed. She had tried, and her hand gave up after two t shirts. I told her about rotary cutters and she instantly grasped their benefit.)
For lightweight knit fabrics and worn out t shirts, I’ll often use the hand-held Martelli Ergo cutter. I have the right hand model. I’ve thought about getting one for each hand, but I bought the Jiasew instead. The angled grip takes the strain off your wrist and allows your body to use upper arm and shoulder muscles to guide the cut, rather than your wrist and forearm muscles. The grip also allows you to keep the blade more closely perpendicular to the cutting surface, which reduces wear on the blade edge.
Given that manual rotary cutter blades cost about $5 each, you’ll do well to invest in a blade sharpener. I use the Dritz model. I can get about 4 sharpenings per blade, which reduces the effective cost to $1/blade and pays for the sharpener in about 4 blades’ worth of cutting.
Just this year, I finally went to the Jiasew electric fabric cutter. This is a low-end model; cutters designed to cut denim at a full-time level have much bigger motors and scary blades. Sometimes, it gets a little caught up in some slinky fabrics. Using an electric cutter has allowed me to process denim blue jeans economically, something I couldn’t do with a manual rotary cutter.