I've struggled with getting my blocks to come ou precisely for years; don't know whether it's the inaccuracy of my 1/4 inch seams or something else but I've finally just begun to either paper piece the block or make the units a little outsized and trim everything back to the precise measurement I'm after. It's a little more trouble in the short run but saves a ton of frustration when I start assembling all the blocks.

This is what a friend of mine told me long ago and she was a quilting teacher and an avid quilter herself. Tried it and it worked.

I did pretty much the same thing only I used an old magnetic business card. I just cut out the area where it went over the feed dogs. I can't adjust the needle on this machine. I have a vintage Kenmore. Works just fine and it's easy to move if necessary.

I took a very expensive precision piecing class a few years ago. Once you find the seam allowance you want then the secret is to sew very slow. Slow Slow Slow. One stitch at a time. It won't be long until you can sew a perfect 1/4" seam without any guides at all.

Not being able to sew that required 1/4" caused me so many tears and lots of rip it rip it time. I was feeling like I could do nothing right. I finally bought a 1/4" pressure foot and found the sewing experience amazingly better. Even my 10 year old grandson can sew that perfect 1/4" seam!

Not only are the seams uniform now. It has made matching seams and points much easier. I still check seam measurements to make sure all is well. The scant 1/4" is just okay....have not learned a precision way to judge that seam.

I have a Pfaff and discovered that I had to move the needle way over to get the 1/4" seam.
Why would anyone design a machine that way? Oh, what a question. I'll let someone else answer that one!! :-)

coopah, remember that some people who use sewing machines use a 5/8" seam (referring to the garment makers). A lot of clothing patterns call for a 5/8" seam. The easiest way to accommodate both is to start the needle in the middle and let it be up to the machine operator to adjust the needle position. Some of the newer quilting machines have a shortcut button to sew a 1/4" seam with the 1/4" foot. The Janome 8900 has that feature.

I found that the specialty 1/4" quilting foot caused me more problems than it helped. I have an older Bernina and bought the new patchwork foot thinking it would help me. Nope. It caused me to slightly veer off at the ends of seams for some reason and I didn't have good visuals at the ends either. I found that I still needed a long line accurately marked on the machine bed with the needle to the right side so that the feed dogs have better contact with the fabric. You can use all manner of things to mark your line-- blue painter's tape, 3-M removable mounting squares, sticky-back moleskin, a stack of post-its, etc. I found that I really needed something with height so that I had something to butt up against. Stitching inside the quarter inch ruled lines on graph paper or index cards is great for measuring the scant 1/4" distance. It is useful to check your measurements fairly frequently on sample blocks because things can slip or wear down, and as has been said above, thread and fabric can make a difference.

I finally invested in one of those inexpensive seam guide rulers with a hole for inserting the needle and a long edge to place your seam guide material of choice. The last time I was at the Bernina dealer, I bought one of the screw in metal seam guides for an insane amount of money I thought, but it is easier than frequently replacing tape, etc. when I have to sew a 5/8" seam on clothing. It works on my old Singer 15-91, too.

Up until the last few years every box of accessories came with that metal guide, I have 4 machines and 7 of the guides :) don't ask me how. You can also buy them off ebay very inexpensively.