Thats what I do too.

one way is to put your needle down, put a small ruler against the needle and find the 1/4" mark...put a little dot...mark a couple dots in line...just inside of the 1/4" mark so you have a scant 1/4"...then run a piece of masking tape along your dots...so you have a guide that is straight and a scant 1/4". sometimes when a pattern calls for scant seams people will cut larger...stitch then trim to size instead of having to deal with it...but i have found a guide on the machine works pretty good.

I measure from the needle to a place on my machine and lay down a piece of blue painters tape. It doesn't leave residue and is easy to see. I do have a 1/4" foot and know that scant is just inside the right finger. I can't move the needle because of the single center hole in the foot.

I picked up a 1/4" foot at a quilt show. You can purchase one from The quilter's Portable, 208 South Street, Mallard, Iowa 50562. 712-425-3478. I wouldn't be without mine. In fact, I have two. One that I keep on my sewing machine when I am going away to quilt with a group.

When teaching new students about setting up their sewing machines, I use this technique:

Cut 3 pieces of fabric each 1 1/2" wide by 6" long with 1 piece from a different fabric. Sew the 3 pieces together with the contrasting fabric in the middle. Press seams and measure the width of the center piece. If it is 1", you have your perfect 1/4" seam. If not, you need to adjust your needle position. I have them use a longer stitch than usual so it is easier to rip out and sew again. Keep trying until you get it, then write all your settings down for the next time.

I have (and love) the 1/4" foot with the little black "wall" against which you run the fabric to sew. HOWEVER, the needle position still needs to be set. For my machine, I need to move the needle from the default setting of 3.5 over to 4.2. On my older Janome, I don't need to move anything - go figure!

A scant 1/4" is only the difference of about a single thread's width. This is done because when we press seam allowances, the fabric goes up and over a teeny, tiny bit before lying flat, so we need to allow for it's detour by taking a teeny, tiny bit smaller seam width.

Oh my another problem I have, but then there are so many. I have been trying for at least 8+ yrs to get that scant 1/4" but so far haven't figured it out. I have marked and moved and even cut bigger. Nothing works for me. One of my problems to and I don't know if it is yours also but I can't sew a straight line for anything. I am sure that would help with the accuracy. That I have worked harder on than the seam allowance lol.. Oh well.

Rita

What kind of machine do you have? I would love to do that with my machine but I am not sure if it will make that slight of a movement. I have the Brother CS6000i

1have a janome 3160. How. Do I move the needle?

The simple piece of painters tape works great for running your fabric along, cheap too.

My Pfaff QE's quarter foot has very small notches on the side. I run the edge along the crotch of the notches and it seems to be a good "scant" quarter.