Apparently not close enough. I was putting them about 9" apart, and getting puckers/folds in the back. That's why I switched to spray basting.

about every 4"---or each time you place your fist you touch a pin on each side (4sides)
i do try to make sure they are not in the line of stitching- so i don't have to worry about hitting them- or having to move them when i get to them- so if you have your quilting pattern drawn on the quilt top try to place the pins outside your quilting lines- i very very seldom use pins- (hate having to remove them & find them a pain to put in in the first place- if i have to baste a quilt sandwich i use the thread basting method- it is so much easier to just thread a needle & stitch huge stitches in a grid to hold the sandwich- the thread is much easier to remove after quilting and (for me at least) holds much better than pins

I try to pin no more than 5" apart. Sometimes it will depend on the batting you are using. You are better to pin too close together, than too far apart.

I use safety pins about 4-5 inches apart - gives plenty of stability and the fabric doesn't shift when quilting.

I like the basting spray instead of pins.

I use safety pins about a hand width apart in all directions. It was an investment to start with to purchase that many safety pins but I have used them over and over. I'm reading all the comments about pins falling out and poking and have to assume those posts are talking about straight pins. I would never use straight pins on something that has to be moved around so much as a quilt in a machine. I also use a hand tool called Kwik Klip by Paula Jean Creations to close and open my safety pins as I'm pinning and unpinning. Really makes it much easier and wouldn't be without it. I've never had a problem with puckers using the safety pin method.

It sounds like you are generally happy with your pin basting process, but you might take a look at this technique by Sharon Schambers. I had terrible trouble with puckered backs until I tried this method. You do have to find boards the appropriate size for your quilt, but the rest is so easy compared to pinning or otherwise hand basting, and you can do it from a chair instead of on your hands and knees.

http://www.youtube.com/watch?v=HyaLs..._h42qQ&index=6

I thread baste when hand quilting, pin baste with curved pins when machine quilting. I baste a hand width apart in a grid.

Thank you for this suggestion.

I like to pin baste about 3 inches apart. I avoid pinning where I will sew to stabilize or SID.

If I baste with pins I use 4mm patchwork pins and Pinmoors every four inches. I use Elmers Washable School glue for quilts larger then crib size. The Kwik Klip is a must have if you use safety pins and also the plastic covers for the back of the safety pins make the process so much easier.