For some reason, I've ended up with a sleeve circumference that is 4" larger than the armhole (as it's based on width). This is clearly too big – what's the right way to reduce circumference?
I got a slightly larger sleeve circumfrence too. Then I realised I failed to take out 3/4" for the seams in the underarm at .44 for the side body panel since that's going to be taken out before the sleeve is set in and shouldn't be counted in the armhole's circumfrence. If you happen to be drafting a side body as well maybe take that out and it should get you at least a little closer to the mark.
You will usually find that the circumference of the armhole is equal to half of the chest. This is a good guide, so you know you haven't gone wrong somewhere in the draft.
I got a slightly larger sleeve circumfrence too. Then I realised I failed to take out 3/4" for the seams in the underarm at .44 for the side body panel since that's going to be taken out before the sleeve is set in and shouldn't be counted in the armhole's circumfrence. If you happen to be drafting a side body as well maybe take that out and it should get you at least a little closer to the mark.
There are also two ways of measuring the armhole circumference. The Cutters method and the coat makers.
The cutter measures on the edge and the coat maker measures 3/8" back on the sew line. I use both.
I would measure the armhole on the edge to work out the sleeve width and then back 3/8" from both the armhole and sleeve to work out fullness.
You will usually find that the circumference of the armhole is equal to half of the chest. This is a good guide, so you know you haven't gone wrong somewhere in the draft.
Sleeves have often been considered an enigma by many Savile Row cutters.
A saying that was used time and again was 'keep it simple'.
And you couldn't get any more simple than the sleeve draft.
If your pattern has high shoulders, the system will produce a small sleeve cap, and if the shoulders are sloping, it will be long.
Reduce it at the underarm where the hind arm is (that is, the side of the underarm where the vent is).