When I took a quilting class the lady had us use a 1/4" squared graph paper and use it to be sure our machine sewed a 1/4" seam. I just put the paper under the foot making sure the first line of the 1/4" was at the middle of the feed dogs and then used the hand crank to pierce the paper with the needle. You would be surprised how much that helped. If you are off much perhaps you could move your needle position. Another good trick is to be sure to measure the 1/4" and then use painters tape to keep you in line. Hope this helps.