If you are confused with stitch lengths, then here’s a video I made to help you better understand how it works and when to use it. I am going to talk about straight stitch lengths only. There are various stitch lengths to choose from but each comes with a purpose. When deciding on stitch lengths there are several factors to consider.
Is it a topstitching prone to wear and tear? Say, for example, when sewing an outer pocket on a wallet. An outer pocket is prone to straining and the stitches might come off easily. This is the reason why you need shorter stitches, around 1.8 mm to 2.0 mm, to tightly hold the fabric together.
How about topstitching without wear and tear purposes? Here you can use a longer straight stitch length around 3.5 mm. This seems to be more of a decorative finish and to hold things together. You cannot use shorter straight stitch lengths when sewing multiple layers of fabric together because it can cause your machine to hang up and may not be able to feed through all those layers of fabric easily. Also, consider denim stitches, using longer length allows the stitches to pop, be more defined, and be easily noticed. Besides, you are stitching through thick denim fabric and with a seam allowance that’s why you need to use longer stitch lengths.
Lastly, topstitches on straps of tote bags. Straps of tote bags are made to hold all the weight of the bag. What you need is the kind of stitch that will tightly hold together all the layers. A stitch length, around 2.0mm, not too short because again you cannot sew multiple layers of fabric with shorter stitch lengths. Also, not too long stitches because every time you tug the straps those stitches will pop out over time.
These tips will help you decide when to shorten or lengthen your stitches for a better quality project. Happy stitching!