I've accumulated a lot of left over bits of 4-ply sock wool. I weighed it the other day - over a kilo
-, so I've been looking at using it to make a 'tasteful' (ie garish) garment. I found a simple round necked jumper, suitable for 4-ply (allegedly) and knitted from the top down (why not experiment) It is knitted on 2.5 and 3.5mm circular needles. According to my admittedly ancient needle gauge these sizes do not exist. I have got a 2.5 set, and a 3.25 and 3.75 set. In 'old money' 4-ply was usually knitted on 12s (2.75mm) and 10s (3.25mm).
The tension for this jumper is given as 21 sts and 24 rows to 4"/10cm using 3.5mm needles. I have tried out both 3.25 and 3.75 needles and get nowhere near that - 26 sts and 34 rows on 3.25mm and 24 sts and 32 rows on 3.75mm.
I have an old pattern (price 1s/5p so pre-1971!) for a 4-ply cardigan knitted on 12s and 10s and the 3.25mm tension square is spot on for that.
Do I try a 4mm needle or decide the pattern maker is lying and back engineer the cardigan?