Objective: Sew a clean French seam on the Janome MC6650 and configure the machine's production-oriented settings so your home-business items have fully enclosed, durable raw edges.
A French seam encloses the raw fabric edges inside the seam itself, so there are no fraying threads visible inside the finished item. This matters for a home business because it signals quality on products customers inspect closely, like scarves, pillowcases, and children's clothing, and it eliminates the need for a serger. The idea is to sew the seam twice: first with the fabric WRONG sides together, trim the allowance narrow, then fold so RIGHT sides are together and sew again, trapping the first seam inside. On the MC6650, three features make this precise and repeatable: the needle up/down button so the needle stops in the fabric when you pivot or pause, the speed-control slider so you can run slow on the narrow second pass, and the adjustable needle position plus the markings on the needle plate so you can hold an exact 1/4 inch then 3/8 inch allowance. Think in terms of a total seam allowance budget: a standard 5/8 inch seam splits into roughly 1/4 inch (first pass, trimmed to 1/8) and 3/8 inch (second pass).
Example: Making a pillowcase side seam: Place two panels WRONG sides together. Select straight stitch, center needle, set the speed slider to about 60 percent. Sew at 1/4 inch using the needle-plate guide line, keeping needle-down engaged so it holds position if you stop. Trim that allowance down to about 1/8 inch and press the seam flat, then press it closed. Now flip the fabric so RIGHT sides are together, with the sewn edge on the fold; press again. Sew a second line at 3/8 inch from that folded edge, slowing the slider for a crisp finish. Open it out: the raw edges are now completely sealed inside a tidy tube of fabric.
Try it: Take two scrap rectangles about 8 by 8 inches. Sew a French seam along one edge: first pass wrong sides together at 1/4 inch with needle-down active, trim to 1/8 inch, press, fold right sides together, then second pass at 3/8 inch with the speed slider lowered. Open the sample and check that no raw threads are visible from either side. Keep this sample as a reference swatch.