Precision Paper Piecing

Spools of threadPaper piecing is easy and fun, but some blocks (particularly intricate, geometric designs) require a certain level of accuracy in the sewing and assembly to look their very best. Try one or more of the simple techniques below to help you achieve the most beautiful block possible.


  • If needed, temporarily hold the first fabric piece to the foundation with a straight pin or a tiny dab of glue stick.
  • When paper piecing, take care to sew accurately not directly ON the printed seam line, but just ever so slightly to the RIGHT of it. This helps accommodate the slight bulk of the fabric’s thickness. When you flip the newly sewn fabric piece open and press it, the fabric seam will sit accurately over the printed line.

  • Press before you sew – what I think of as “press basting.” Place into position the next piece of fabric to be sewn and check the alignment by holding the work up to a strong light. Then press the newly positioned fabric piece with an iron — cotton setting, NO STEAM! — before sewing. The pressure and heat of the iron makes the cotton fibers “stick” just enough to help keep the pieces from slipping when turning the foundation over and during sewing. For me, this one simple step has virtually eliminated those nasty slipped pieces that must be ripped out and re-sewn.
  • After sewing each piece, use your fingernail or a little wooden “iron” to sharply crease the fabric open before pressing with the electric iron. To keep a large piece open and in place while sewing the next seam, try pinning it tautly to the foundation, out of the way of the next seam. My favorite pins are the super-fine Swiss Iris pins – their thinness causes much less of a pinned “bubble” or distortion than other dressmaker pins.
  • After sewing the last piece onto a unit, press the entire unit well on the fabric side. Then return to the machine and set the stitch length to a long stitch (4-5 per inch). Sew a line of basting in the seam allowance around the entire unit, about 1/8” to the RIGHT of the printed edge. Now trim the outer seam allowance to 1/4” using a rotary cutter and ruler. This step will greatly improve the neatness of your finished units and makes it much easier to sew them to other units.


“How do you join paper pieced units without slipping when they’re still backed with paper?” you ask. “I’ve placed the two pieces together and carefully aligned the seam’s end points with a pin stabbed through each end, and pinned along the entire edge. But I still have problems getting the seam sewn accurately!”

First, finish sewing the individual unit properly as described in the above section.  Some people find this step to be unnecessary, but I think the little bit of extra effort is worthwhile, especially for those precise geometric, multi-sectioned designs.

Then try the tips below — you may prefer one method in one situation (such as joining two small half-square triangle units) and maybe a combination of methods for another situation (such as joining two oddly shaped units with lots of seams to sew over).

  • Use thin straight pins to pierce through the critical match points along the seam when sewing two units together. To the extent possible, give priority to matching points important to the block’s design, even if it causes the seam’s endpoints to be slightly off.
  • As when paper piecing, stitch all seams joining units just slightly to the RIGHT of the printed line, to accommodate the bulk of the fabric when pressed open.
  • For tricky seams with multiple match points, hand or machine-baste first. Check your work. When you’re satisfied, resew the seam with your usual stitch length. It’s much easier to rip out a bit of basting if needed than 20 stitches to the inch!
  • If your seams shift a bit when sewing, try using your walking foot.
  • If you’re still having troubles with a particular seam, begin sewing in the middle of the seam and sew to the end. Remove the piece from the machine, turn it over and sew the rest of the seam from the middle outwards, overlapping the stitching a bit. This works well for sewing over multiple seam intersections, or securing a critical match point before sewing the rest of the seam.
  • Use plastic-coated paper clips instead of (or in addition to) pins to hold the seam edges in place, removing them as you slowly sew the seam. If you prefer pinning, try switching to those wonderful ultra-thin Swiss Iris pins for the smoothest possible pinned edges.
  • In addition to securing the edges of the two units to be sewn, pin them together about 3/4 – 1″ below and parallel with the seam line, out of the way of the presser foot (so you don’t have to remove them until after the seam is sewn). This helps stabilize things especially when your foundation pieced units are rather large.
  • Use tape to hold the pieces in position — over the top of the seam edge and even around the sides of the pieces so that the whole thing is secure. Try washi tape, masking tape or even that pink hairsetting tape with the pinked edges — great for times you want a bit of extra hold and easy removal with no sticky residue to gum up your needle.
  • Apply a bit of water-soluble glue stick or basting glue (e.g. Roxanne’s) in the seam allowances if you’re really having troubles holding things in place, and plan on washing the finished project. The glue vanishes in the wash.

I invite you to leave your favorite paper piecing tips in the comments below.