we had a conversation about this recently in another thread.
it turns out that even though 1/4" feet are designed especially to achieve a 1/4" seam, the default needle position differs among brands and models of machine. soooooo even if you're using the 1/4" foot made especially for your machine you might not get that 1/4" seam without adjusting the needle position.
for example, i have two different janome models. if i use the 1/4" foot on the first machine with the needle in the default position, i automatically get a scant 1/4" seam. i must adjust the needle position to get a full 1/4".
the second model has two different 1/4" feet. using the first foot with the needle in the default position, i get a perfect 1/4" seam, so have to adjust for scant. using the other foot i have to adjust the needle whether i want a full or scant 1/4". fortunately, the package instructions included the required setting.
considering all the different makes and models of machine, plus all the different styles of 1/4" available, it's no wonder we are still confused! :lol: :lol:
p.s. - a scant 1/4" is really 3/16th". adjust your needle one or two clicks to the right and c'est voila!