A recent comment reminded me that the rest of the world may not be familiar with a tool that I just take for granted. It is my Darr Piping Ruler. Making piping is a must have skill in heirloom sewing and smocking, but truth is, I like piping on everything. It is that little spark of extra effort that accents an interesting shape or lights up a timid textile. Here are my piping tools: a Darr piping ruler (NAYY), rotary mat, cutter, and ruler, a 5 groove pintuck foot, and some crochet cotton. Sewing maven, Betty D., recommends #3 cable crochet cotton. I have had a giant ball of something similar so long I am not sure what it is. Looks like Betty's cord, though.
The piping ruler is only 8 inches long but that is one of the things that makes it work. It has deep grooves underneath at well marked 3/8, 5/8, etc. seamline measurements.
Heirloom patterns generally have 3/8 inch seams. For that size seam I like to cut 1 1/4 inch true bias strips using my rotary cutter and Olfa ruler. This gives me more seam allowance than I need but you will soon see why. I line up the 45º line on the selvedge of the piping fabric. Make sure the ruler is to your left and the bulk of the fabric to your right for safer cutting. Lefties would be opposite. There are many other ways to make bias but for most children's garments that just require a neckline and cuff edge piped, the short edges of a half yard of fabric cut this way do fine.
Fold the bias around the cord, matching the cut edges. Using your 5 groove pintuck foot, stitch the piping with a 2.0 stitch. I use the groove second from the left and a 3 needle position at this point. I increase the stitch length to 2.5 and then 3.0 in the next two passes attaching the piping to the garment. This increase in stitch length accommodates the increase in fabric thickness and layers, preventing puckering and a shortened seam. You will need to adjust the needle position each time you stitch to get closer to the piping cord.
OK-piping is completed. Lineup your piping ruler fitting the cord into the 3/8 inch groove, or whatever applies. A wider SA will require a wider bias strip. Cut off the excess SA with the Rotary Cutter. Push the ruler up the cord, keeping it in the channel. Rotary cut again. Continue to push the ruler up the piping cord and cutting once in place. You will be left with absolutely perfect 3/8 inch seam allowances. Once this edge is lined up with a garment edge and stitched you will have the perfect 3/8 inch seam. Stitch your piping to the garment going a hair closer to the cord and with a 2.5 length. Add the facing or other patttern piece, matching edges. Now, FLIP THE GARMENT OVER. You will see the stitching line perfectly. Stitch a hair closer again to the piping with a 3.0 length.
You should now have a very nicely installed piping. Many times piping needs a little further tweeking. Don't feel bad if it does. Just keep tweeking. Further treatment of the SAs depends on their location and function so I will save those options for another day.
My little bishop is near ready for its piping so I will try to have pics for that shortly.