I got a couple of questions in my email about doing 2 sided quilts. I thought I should add the answers to my blog for future visitors. The questions were about having two quilts the exact same size and how to attach them to the machine. With quilting machines (on track tables) the backing should be larger than the top in order for the clamps and leaders to hold the quilt sandwich.
Usually one of the quilts will be larger than the other so the largest becomes the backing. If both are the same size....
A false border can be basted to one of the quilts so you have extra room for your clamps and leaders. It's the same principle as you would do when a customer brings a backing that's exactly the same size as the top. Baste a false border on the backing before attaching to the machine and remove it when the quilting is finished.
This would be a pain if I tried to do it by hand. I baste the false border on with my domestic machine. I do a zig zag stitch set at widest and longest my machine will do. On my machine this happens to be a quarter inch wide and 4 stitches per inch. This is the seam allowance for attaching binding so it works out fine when the false border is removed. I keep several long strips of scrap muslin just for using as false borders. I cut these to fit a current quilt and sew them back together for longer quilts later.
I do stabilize the whole quilt sandwich (before stitching any of the design) being careful that the edge of the top quilt lines up along the basting of the false border. This way I know the false border is not going to be stitched by accident. The top quilt will over lap the false border by a quarter inch because of the zig zag seam. When the false border is removed (after the quilting is done) both the top and back should be even.
To stabilize the quilt sandwich; I do a stitch in the ditch around all the blocks (not the individual pieces) and the border. I make sure I don't go over any fabric warts when I SID. If a wart happens to fall in the SID line I skip over it. The warts are usually no larger than a quarter inch and rarely happens more than once or twice so it doesn't show much in the finished quilt.
If I do all the SID and everything lines up nicely along the edges; I know it's ok to go back and quilt all the designs. If for some reason things don't line up; a single line of stitching is much easier to remove than a whole design is.
If for some reason either of the tops is smaller than the other.... you (or the customer) must add a border to the smallest one or cut down the largest one. There is no other choice because the edges must meet to attach the binding.