This is my first sewing tutorial for sewing set-in sleeves flat - please forgive the photo intensive entry and anything that is not too clear. Here, I am testing some refinements to my cap sleeve pattern. I am doing the sewing with my domestic Singer 501 (a fabulous machine, btw). The technique is essentially the same on a 4-5 spool serger or industrial straight stitch machine. Some of this is my personal opinion, some fairly standard fabric handling techniques. Please note, my sleeve pattern has no ease.
Place the sleeve against the feed dogs, the body on top. Notice that I am using no pins, no basting, and no ease stitching. There is a single notch at the center of the sleeve cap. My sleeve is symmetrical front to back so there are no extra notches to indicate the back or front of the sleeve. Adult clothing would have extra notches, so make sure to match up fronts or backs or you will have a funny looking sleeve.
Do you see the placement of my hands? My left hand is holding the body and my right hand is controlling the sleeve. This is one of the major differences of industrial vs. home sewing. Home sewists like to pin the two layers together and have everything move together in lock step. With this method I can control the two layers as they move under the foot by ever so subtly pulling or pushing. It takes time, practice, and confidence in your pattern to develop this skill but it is absolutely essential.
This picture just shows that the shoulder seam and the sleeve notch meet up. Another industrial technique is that the operators will tap the foot pedal. Home sewers press down on the foot pedal like they are at the races. But during certain operations, the operator can gain more control by tapping the foot pedal. This can help while going around a curve.
This picture tries to illustrate why the sleeve should be next to the feed dogs. If there is any ease (and it should be minimal) the feed dogs will do the work of easing for you. My sleeve has no ease so this picture isn't accurate. If there were ease, it would look something like this on the inside.
This is a view of the top of the sleeve cap. There seems to be a few puckers, but that is a combination of poor lighting and the fabric - a poly-cotton broadcloth. The sleeve cap is actually nice and smooth.
Stitch the side seam from the waist to the sleeve hem making sure the armscye/sleeve cap seam allowances are turned toward the sleeve. The seam allowances, when turned in the right direction, will fill the sleeve cap and help give it a nice rounded shape from the outside. Some operators will allow the seams to lay in opposite directions (for bulk, they may go in opposite directions, but otherwise they shouldn't).
The finished sleeve.