Johanna Fritz

I have made pinwheel units that are paper pieced, where 8 quarter units are all meeting in the middle. I always sew on the sewn line. You never sew past the sewn line (back tack or spin the unit North to South, facing you, so you are sewing back over the stitch line without having to use the "go backwards" switch. If you sew this way, you should be fine.

Also, when you join units at the center, (as in your example) - you join 2 units together to make 1/2 of a square. Start sewing in the center, where pinwheel is, and sew outwards to the edge of the block. Join the other 2 in the same way to make another 1/2 of your final square. Then join the 2 halves together, making sure to sew right on the line, and start from the center. I have a mini light on the side of my machine, shining at the needle. June Tailor makes "Perfect Piecing" (at JoAnn's). It is a very thin, almost interfacing like material, that you can leave in if you like. You don't need to flip it over to see thru it. There is also "wash away" paper that disappears. Both of these work with my mini 4" and 6" pinwheels. Good luck.