Yesterday I was teaching the “Learn Your Machine” class at Bonny’s and a customer asked me “What are those markings on the metal plate?” She was talking about the markings on the stitch plate and I thought at the time, “What an excellent question!” If you are new to sewing or if you have not sewn for an extended period of time, the lines on the stitch plate may not make much sense. Most machine manufacturers sell their products globally, so creating the markings in the metric system is the most cost efficient. If a stitch plate with markings in inches is available for your machine, you may want to invest in this, usually, optional accessory. The lines on the stitch plate are there for you to use as a guide for your fabric, allowing you to maintain a straight line of stitching.
If you are using a plate that has lines with the designations of 1, 2, 3, etc. this is probably a stitch plate measured using the metric system. By following these lines, you are stitching at a specific distance from the needle when it is in center position.
The above are approximate measurements since the metric system does not line up precisely with inches. Using a stitch plate that is marked in inches allows you to sew more accurate seams since there is no conversion from one system to another. Once you get used to the lines you follow the most for the specific seam size you sew, these markings will be another tool that makes sewing a little easier.