Chain stitching
 

I'm a newbie in quilting. When I start to chain piece my thread gathers, when I cut them apart I have to resew the ends. Why is this?

It usually helps to run off the fabric 3 or 4 stitches. This helps to 'lock' the stitch a little better. I just did a bunch of chain stitching last night. I have the starters and enders and I run 3 or 4 stitches between the pieces and the starters/enders. When I am doing the chain piecing and I am on the last rows and things, I will back stitch a bit on the edges. Usually when I know that that edge is going to be pulled on it with quilting and binding and such.

I think you mean chain piecing? Chain stitching refers to a different type of sewing machine.

It is probably being caused by unbalanced tension on your machine. If this is the case, either the top tension is too tight or the bottom tension is too tight. What kind of machine do you have? If it's not a drop-in bobbin, check out this Youtube video:
http://www.youtube.com/watch?v=Q1mRhcquZTM
Even though it's for longarm machines, the same technique works really well for domestic machines. What you are aiming for is a balanced stitch with the stitches locking in the middle of the fabric.

If you have a drop-in bobbin, I assume you just have to use trial-and-error unless someone else on the QB can advise.

Meanwhile, if the problem persists, you can get around it by simply allowing a gap of about an inch between pieces (more if your pieces are large) as you sew. Cut the thread halfway between and there should be enough thread for the gathering to smooth out without the ends coming undone.

My first guess is your stitch length is too long. Try shortening it.

use at least a 2.2 or a bit smaller.

I usually hold both threads for the first 2 or 3 stitches. And I agree with the previous advice from others - shorten your stitch length a bit, pull the previous piece out just a hair, and know that it's okay and normal for one or two stitches to be loose or pull out on a section you just sewed. Quilting is different from garment sewing in that a lot of quilters don't bother to backstitch.

It took me a couple of years to stop back stitching when I first started quilting. It was a habit from sewing garments. It's amazing how quickly you form a habit and how long it takes to break the habit.
Sue

Try making your stitches smaller. I just butt each piece up to the next (with no extra thread between) and never have any problems. Good luck!