Here's a tutorial on how to sew a two-piece sleeve vent on a lined tailored jacket like this:
With this method, the vent is first constructed, the lining is attached, and then the buttons are sewn on - I don't usually bother with buttonholes, but if you decide to insert them do it before you insert your lining, and there is no need to cut them as they are nonfunctional and purely decorative.
I hope you'll find this tutorial helpful - a lot of people bumble their way through this with bits of handsewing here and there, but it really is very simple to machine sew everything when you know how! And most important is that your pattern is configured correctly and that you understand how the pieces go together. Preparation is the key!
Have a look at your topsleeve and your undersleeve - they should look something like the pattern pieces below. Check you have the following notches - if they're not there add them in as indicated below:
hem notches - on side seams at level of hem fold line. While you are here, fold up along the hemline, and make sure your hem mirrors your outer shell.
undersleeve notch - draw a line from your hindseam stitching line to the lower edge of the undersleeve, parallel to the vent edge, to position this notch.
2 topsleeve notches for the vent mitre - fold back your topsleeve hem fold line and vent fold line, and notch where their edges meet. You can trim the bulk away leaving a seam allowance, but I haven't on this example because I was err... lazy
Now make some fusing patterns just like the shaded areas on the diagrams:
2cm above your sleeve hem
2cm in from each sleeve seamline
3mm in from each cut edge of sleeve patterns
Cut out your fusing patterns, then cut and apply your fusing to your sleeve panels.
Can you spot my mistake?
I have a bad habit of cutting my fusing direct from the shell pattern without going through the process of making a fusing pattern, and you'll notice the fusing on my undersleeve vent is narrower because I was taking dodgy shortcuts. Now this isn't critical so I will run with it, but now you know yours might look a little bit different. (note to self - do things properly!)
Now you can start sewing, but guess what - if you've followed the preparation above, there are only three lines to sew in your sleeve vent! Easy-peasy - here goes:
First sew the hindseam from bottom to top - begin 1cm from the vent edge to allow for a turnback, stitch along the upper edge of the vent ending with your needle down, lift your foot and turn your work to stitch the remaining sleeve seam:
Fold the top sleeve right sides together so your mitre notches meet, then sew from the notches to the fold line, exactly perpendicular to the fold line:
Clip away the excess and turn to admire check your mitre:
Now sew your undersleeve corner - just fold your hem up along the hem fold line, bag out at 1cm and turn corner through:
The hindseam will be pressed open, so clip the undersleeve only into that turning point. Don't worry - this area is all reinforced by fusing, and clipping on the bias means it is even less likely to fray. And once your buttons are sewn on there will be no stress on this point anyway.
Overall you should have something that looks just like this:
the hindseam is pressed open
the undersleeve vent edge is pressed back 1cm (3/8")
the top sleeve vent fold line aligns with the undersleeve notch (highlighted here)
the topsleeve and undersleeve hemlines align - not like this example below!
Sorry, but if you end up with this, you will have some unpicking to do! If you are a couple of millimetres out, it is possible to unpick just the undersleeve bag out, and restitch it so it is level with the topsleeve. More than this, and you need to check your allover accuracy.
Once you have this area looking good, sew your forearm seam, press open and your sleeve shell is done!
Now for the lining.
I use a 4cm hem allowance for my sleeve hems, and this means you can cut your lining to the hem fold, giving you a 2cm allowance for ease in lining length. Cut your lining to this length, omitting the vent allowance as in the diagrams below - blue = lining pattern. (I will save the armhole end of the sleeve for now - that's another tutorial!)
Sew the forearm seam and hindseams of your lining, leaving a gap in one forearm seam for bagging out.
Now sew the lower edge of your lining to the hem allowance of your sleeve shell. When stitching the shell and lining together, note that the forearm seams of shell and lining will meet exactly. But near the vent your lining hindseam will match the undersleeve notch that you really wish you'd made made sure you had earlier on (see photo above). The topsleeve hem is often cut on a slight bias, so to the inexperienced eye it may feel like the two layers don't fit - but if you cut your lining pattern as above and match your notches correctly it will fit perfectly - I'll give you permission to use pins here if you want :) I usually have about a 1cm gap in my stitching around the vent, but that is OK, it presses upwards, and will be enclosed when you attach the buttons.
Don't press your hem yet though - you need to tack the hem up at the forearm seam first! Fold the forearm seam along the hem fold line, and from the inside grab the seam allowances lying face to face on one side of the forearm seam and sew them together. Use your handy-dandy hem notch as a folding guide, line up the cut edges of the seam allowances, and backtack about 2cm above the hem fold. Now you can turn your sleeve through and safely press.
Sew your buttons on through all thicknesses. Your lowermost button needs to be attached through the hem layers to ensure the corner of the vent sits flat. In my example above they are a bit too high and the corner of the vent curls out - not pretty on a 3/4 sleeve! I will be repositioning them at my earliest possible convenience :)
Hope this helps for happier sewing!
