What am I doing wrong w/Lastin?

If you're doing a casing for your elastic, I would say don't use the lastin - go with a polybraid type. Lastin snaps very easily if punctured, so that's why it's best used fully zig-zagged down.

Yup. You aren't supposed to just tack the lastin ends.

Lastin is great though!!
I sew mine in a three step along the seam allowance,i.e when I get to the seam allowance section which the lastin needs to be I simply sew about 1/4 inch onto the lastin with the straight stitch,then pull it taut and flip my machine to three step and then the straight stitch at the end for the last 1/4 inch!

It seems to work nicely,I have only ever sewn casings with regular elastic.
It is a fast way to work too!!!!

Love jayne

Yes, I too learned the hard way not to use Lastin just stitched at the ends. Twice I had to cut a slit at each end of a pocket casing to rethread another piece of elastic to replace the ones that snapped even before we tried out the diaper. Now I do the 3-step zigzag instead.
Jayne, what width Lastin do you use? Also, how far do you stretch it? I have been experimenting with 1/4-inch and 1/2-inch. It's very stretchy, isn't it? I've tried roughly measuring 1/3 of the final length as I stretch it to sew it down, but it's able to stretch even more. Do you stretch it as taut as possible or what?

Thanks for all of the advice. I'm interested in answers to GA's questions, too...

What do you do if you don't have a 3 step zig zag?

lhowlett, I've used a regular zig zag with braided elastic fine - I *imagine* it would work well for lastin too, but that's just my opinion.

Nope, lastin says not to use it with anything other than the 3step zz. I use 3/8" most often.

I use a regular zigzag with my Lastin - there's a trick to it though. If you let the elastic bunch up while you're zigzagging it, there's the very probable possibility of the stitches totally missing the elastic altogether. This, in effect, works the same as putting Lastin through a casing - the ends snap, and the elastic just pulls straight through the channel of zigzag stitches!
So, if you use plain zigzag, just make sure the elastic lays flat, and that the stitches actually go through the elastic most of the time. As long as you do that, it works fine.