I'm starting on a denim rag quilt made of 6 1/2 in blocks, no batting in the middle just denim for top and flannel for back. My question is ..do I need to make an X on each block to keep front and back from poofing out? I have never made one before and it seems easy but can't find out about this one thing. Thank you in advance for all help.

Most all that I have seen, and made, do have the X in the middle of the block. I am in the planning stage of a jeans rag quilt made of old jeans from our family. I'm thinking about tying a french knot in the middle of each square. I would be interested to see what everyone else thinks too!!

Yes mine are of old jeans as well. How and with what do you tie them?

I haven't started yet, but my plans are to tye a french knot in the center with 2 strands of pearl cotton floss to match my "other" fabric. You can always use elmers glue to hold the fabrics together while you sew the seams.

I've made many rag quilts. To stitch an x or across the corners to prevent shifting of the back, front and any batting or additional fabric layers depends on the size of the block. Larger blocks should be stitched in some way in my opinion. Smaller blocks could just be tied in the center. 6 strand embroidery floss, knitting yarn and 2 strands of crochet thread have all worked for me for the ties.

I am making one out of flannel right now that is that size and I have not had to sew an X, but flannel might not shift as much as denim. You could make a sample "4 patch" and see what happens. If it shifts that is small enough to put back under the sewing machine and sew the X.
Rose

no, I have made at least 20 denim/calico rag quilts, and you don't need to add stitching or ties in each block unless your squares are really big. I cut mine 6 1/2". Some of the quilts are 10 years old, used by boys and laundered frequently. Some of the calicos are wearing thin, but otherwise there have been no problems. The guys love them. My youngest has his at college with him.

You can also sew a circle in the middle. X's and O's :D:D:D
These circles go quicker than the X's. Meaure the width of your circle. get some tape and a thumbtack. poke the thumbtack up from the sticky side and securely tape it to the bed of your machine, half the width of the circle away from your needle. Finger press to find the center of your square and poke the center onto the thumbtack. Start sewing and you will sew a circle. Don't pull or tug at the fabric, or your circle will be distorted.

Amma, Thanks so much for that tip, I now have learn't something new once again..:}