The armpits are the bit which foxes most people. I have seen more reconstructions of mail shirts which lack armpits than those which have them. If you watch the historically all-over-the-place film Braveheart carefully, you will see the king of England lift up his arm during one of the battles, to reveal that he has no mail under his armpit. It seems that even the armourer of so high and mighty a man balked at having a go at doing the armpits. At one live-action role-play event, I remember joking that people's under-arm sweat must be very corrosive indeed. In truth, you need not fear doing the armpits.
I have not seen two shirts which handle the armpits in the same way. This means that we have some licence in the way we do it.
Here we see the armpit as it is handled on shirt A2. We are looking up at the front of the shirt at a funny angle, and not all of the shirt is shown. The arm hole is shaded grey, and is arch-shaped rather than round or a slit. The base of the arch is created by a hiatus line of twelve links. At this line, the direction of the grain, represented by green lines, changes. The manner of linking between the two directions of grain seems to me to be pretty ad-hoc, following no formal pattern.
The red dots are hole contractions. Seven are in a line which goes from the front of the hiatus line, towards the sleeve end. This line has the effect of narrowing the sleeve towards it opening, and because it is not aligned with the centre of the hiatus line, but with its front, it also has the effect of bringing the sleeve further to the front of the body. Also, unnoticed by both de Gorey and Burgess, there is an
isolated hole contraction between the other end of the hiatus and
the sleeve end. This extra contraction is less easy to spot,
since it is reversed (difficult to explain what I mean by
"reversed" it acts to reduce the width of the sleeve in the same
way, but it takes place where the lie of the rings is the other
way around from the line of seven, so that the rings around the
hole are seen with edges showing where the profiles are presented
in the line of seven). This means that there are a total of eight
contractions in each sleeve (Burgess spotted seven and de Gorey
I agree: this is not the world's best diagram ever, but this is not an easy thing to illustrate. Here we see the grain pattern on my shirt, where there is no hiatus. This is simple, and it works fine. Start making the mail for the sleeve by extending the top of the shoulder from the neck hole. Keep trying the shirt on until the length of the sleeve is as long as you want it on its top side, then broaden this strip to cover the shoulder's front and back, and just keep going. It will all work out fine. Trust me. Eventually, the two directions of grain meet at a single point. Link as seems appropriate at that point. If in doubt, put in fewer links rather than more at this point, because you don't want a knot of mail under the arm.
Now, just to show you one of the many alternatives, here's a grain pattern for the armpits from a Moghul suit. The grain comes up the side of the torso, and then carries on under the arm towards the sleeve end, but this piece of mail diminishes to a point, forming a long triangle under the arm, with two long lines of hiatus. Complicating this arrangement, is the fact that the rings near the chest are very big and chunky, while those at the sleeve ends are smaller, and the change is fairly gradual. The links joining the two sides of the hiatus tend to be smaller than those either side of that join. This probably helps to keep things neat.
Now I hope that you will never feel the fear of doing armpits, and that you will make a fine pair of them, which will be the envy of all your mail-wearing friends. You may wonder what all the fuss was about, but don't let on: instead maintain to the last that it is very difficult to do armpits, which in fact it isn't.