Know Your Sewing Machine

if you did the practical start course, you can already thread a machine and sew a straight seam. this course is about what is happening while you do, because the difference between someone who sews and someone who fights their machine is that the first one knows what each part is for. a sewing machine is not a mystery box. it is about eight parts that matter, doing the same dance five hundred times a minute.

you do not need a new machine for this course. the one in the cupboard, the one from the charity shop, the hand-me-down: almost any working machine from the last forty years can do everything taught here. if you are buying, buy boring and mechanical.

The stitch, honestly explained

a machine stitch is two threads locking around each other in the middle of the fabric. the needle carries the top thread down through the cloth. as the needle rises a few millimetres, the thread bulges into a small loop, and a rotating hook under the plate catches that loop and swings it right around the bobbin. the two threads are now interlinked, and the take-up lever snatches the knot tight so it settles inside the fabric layers.

everything about tension follows from that picture. a lockstitch looks right when the knot sits in the middle, invisible from both sides. if the knot is being pulled to the top, the top thread is winning: its tension is too high, or the bobbin's is too low. loops underneath mean the opposite.

Tension without fear

the tension dial adjusts spring pressure on two discs the top thread runs between. that is all it is. middle of the range (usually 4 on a dial of 0–9) suits most fabric with matching thread top and bottom. test on a scrap folded to two layers before every project, look at both sides, and adjust one number at a time.

the rule that saves the most grief: tension faults are nearly always threading faults. before touching the dial, rethread completely, top and bobbin, with the presser foot up. the foot lever opens and closes the tension discs, and a machine threaded with the foot down has its top thread lying uselessly on top of closed discs. this one mistake accounts for more abandoned machines than any mechanical failure.

Needles are consumables

the needle is the cheapest part of the machine and causes the most faults. sizes run 70/10 (fine, for lawn and lining) through 80/12 (the everyday size), 90/14 (denim weight, canvas, two layers of towelling) to 100/16 (heavy canvas, upholstery weight). the bigger number is the shaft diameter in hundredths of a millimetre; too thin a needle for the cloth deflects and snaps, too thick punches visible holes.

point type matters as much as size. universal points handle woven fabric. knits need a ballpoint, because a sharp point cuts the loops of the knit and the fabric ladders like tights. jeans needles are reinforced for dense weaves. change the needle after every project, or sooner if you hear a punching sound on entry: that is bluntness, audible.