Have you ever been asked to sew a "scant" quarter inch seam allowance? Technically, is a just a little bit less than a quarter inch seam allowance. A lot of times I will find instructions calling for a scant seam allowance when making half square triangles and quarter square triangles, sometime even flying geese. What they are trying to do is to provide a little bit of wiggle room in your block so that you can go back later and square it up through trimming.
This is what a true quarter inch seam looks like on my machine, using a quarter inch foot.
You can find out what your true quarter inch on your machine is by using a ruler. Place the ruler under the presser foot, with the foot down. Position the ruler so that the needle is directly at the 0 point on the ruler. Look and see where a 1/4 inch falls. For some feet it is directly at the edge of the foot. Other times it might be just on the outside edge. Or like my machine, it is right on the edge by a little bit on the inside edge.
Here is what I would classify as a scant quarter inch seam. It is more than a few threads but less than a 1/16 of an inch towards the needle.
I have heard a "scant" described multiple ways. I have heard that it is a 1/16th of an inch, and I have also heard it is just a few threads. I feel like it should be some where in the middle. But of course, like everything I put on this blog, this is mostly my opinion and you are welcome to make your own decision!
Something else I learned is that they use the term "scant" in cooking too! It is usually used to describe a just a little bit less measurement. I.e. One tablespoon short of a full cup.
(Also, please excuse the linty machine. I am mid-project and my machine is working hard!)
Have fun quilting!