6 mm Needles Yarn Weight in the UK
by RCo7
(East Sussex, United Kingdom)
A yarn requiring 6mm (Old UK size 4)needles would probably be Aran weight, or even chunky. I think the confusion might be because the USA worsted weight yarn category ranges from similar to UK Double Knit weight to UK Aran weight, so the lighter USA worsted weight yarns equate to Double Knit in the UK, while USA heavy worsted weight is closer to Aran in the UK.
My main point here is to knitters in the UK, that is if they wish to use the basic instructions for a square, casting on 32 stitches on 6mm needles, use an Aran or a Chunky that is only just a Chunky. If a UK knitter wishes to use DK weight yarn according to the same instructions, then knitting with two strands at once should do it.