I had purchased a quarter inch foot with a guide/blade, but I was not ever happy sewing with that foot. Somewhere on the web I read that you should try and bump your needle to the right and see if you had enough clearance between the needle and the hole in the foot (of course, I did have my 7mm sole plate on) to achieve a scant quarter inch seam. On this foot I didn't. But I did notice something that may explain some of my dissatisfaction with this foot...the foot didn't cover the feed dogs completely. The right hand most row of teeth were completely exposed. My machine has a tendency to pull to the left and this probably made it worse.
This foot was purchased on Amazon for under $4.00 and covers the feed dogs nicely. There wasn't quite enough clearance to bump the needle over safely, so I asked Sweetie if he could make the hole just a bit bigger.
Here it is on the drill press. It was a success.