How helpful would it be for sewing machine manuals to include the full information about how to prepare the sewn item and how to use the buttonhole foot properly to get decent buttonholes.
It is rarely the equipment at fault and making decent buttonholes is more about understanding what happens and doing the preparation.
Even with a machine that is precision engineered and programmed to stitch beautiful buttonholes, in order to produce decent quality buttonholes, it is still essential to
- stabilise the area;
- control the layers, thickness of the fabric;
- use an appropriate thickness/thinness of thread (sew all thread is often too thick for buttonholes on lightweight fabrics); and,
- (really important) ensure that the buttonhole foot remains absolutely level so that the fabric is correctly in contact with the traction of the feed dogs all the time so that the fabric feeds evenly and properly. It must be level front to back and from side to side. If the foot tips even slightly, the pressure that clamps the fabric to the feed dogs changes and the feed dogs cannot get the correct grip on the fabric to move it consistently and evenly. When you get uneven stitching and stitch pileups that cause the foot to stop moving altogether, that's usually because the foot was not kept level throughout.
This next bit is really, really important and the key to all machine made buttonholes.
Often we test the layers on a flat sample and the machine does the test stitch out perfectly however when working on a garment even the teeniest bump of a bit of seam allowance throws things off because the foot isn't completely level, especially at the top of button bands and on collar stands.
Remember when you do the test samples ensure that you must replicate the seam allowances and stitching (ie. all the lumps and bumps) that will be on the actual item to check how to keep the foot level for that section.
Avoid the trap of test stitching buttonholes onto flat fabric scraps - replicate the seam allowances, bumps and edges.
It is worth repeating - to get a good buttonhole on a collar stand and at the top of a placket you must do the test samples on the same sort of seam allowances, lumps, bumps and edges.
Ways to keep the foot level - the simplest is to use folded pads of fabric butted up to the edges of the section of the fabric where you are stitching the buttonhole.
Another is to plan ahead and reduce the bulk from seam allowances by trimming or on buttonhole bands, adjust the pattern to use cut-on/fold facings rather than separate pieces that involve seam allowances.
Most problems with the quality and consistency of buttonholes can be associated with the the feed of the fabric because the long buttonhole foot is not completely level at all times. Even a slight bump from stitching or a piece of seam allowance can tilt the foot and reduce the traction of the feed dogs. This can be the case with even the most high end machine that costs thousands.It's not necessarily the make or model of sewing machine or whether it's computerised or mechanical that makes a great buttonhole, however the advantage with computerised is that the programme doesn't change so everything else about making the buttonhole is controlled by the user.