While sewing 0n my bernina 780 ascrew fell out. I was pulling the fabric because i puy an elastic in

Not sure if this will help, otherwise, I believe Bernina has a Support contact on their web site:

Bernina 770 14 Cleaning the Thread Catcher

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Serging elastic to material

Attaching Waistband Elastic with Serger Coverhem

how to use an elastic foot on serger

How to Serge over Elastic Avery Lane Sewing

Learn to Serge How to Serge Elastic and Ruffles

Measure the circumference of the fabric without the elastic. Then decide the fraction of that circumference you need the elastic to be--ie, if the fabric measures 12 inches and the elastic should be three quarters of that length= 8 inches. Cut the elastic to 8 inches. Stitch the ends of the elastic together.

Then fold the fabric in half and mark the halfway points with straight pins, then fold in fourths and mark those points also. Then do the same with the elastic (marked in fourths). Match the quarter mark pins of the elastic to the quarter marks of the fabric. Then stitch the elastic (stretching as you sew) to the fabric. (Marking and matching the quarter marks will insure the elastic will be evenly stitched to the fabric.)

Video How to Sew an Elastic Waistband Without Casing Threads

Sewing Basics 2 7 Ways to Attach Use Elastic

How do you sew elastic on fabric

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Hm, sounds possibly like an electrical issue. Take it for service.

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try these links for a manual

BERNINA 780 Support BERNINA

Bernina 7 Series B780 Sewing Machine

Bernina 780 Sewing and Embroidery Machine

Bernina 780 Sewing Quilting and Embroidery Machine

here is a link for parts for the sewing machine
http://www.sewingpartsonline.com/bernina-150-sewing-machine-parts.aspx

I am assuming this is a simple stretch waist band with elastic about 2cm wide attached to a skirt or trousers. You need to measure your wist and cut elastic that length plus 2cm. Then join the two ends by overlapping them 2cm and zig zagging the elastic together with regular sewing machine. Now mark the elastic in quarters, ie hold it flat with the join in the middle and mark each edge with chalk or a fabric removable marker. Then put the marks together and mark the edges again so you have 4 marks equally spaced. Now do this for your garment too. It may be bigger in back so mark front and back, then half this to find the side quarters. Put elastic on inside of garment against raw edge and pin the quarter marks on elastic and garment together. Set up overlocker for 4 thread wide seam. Test seam and adjust tensions if necessary. Now you need to serge the edge of the fabric and elastic together, trimming the fabric but not cutting the elastic and stretch the elastic to fit the garment as you stitch. Elastic on top, fabric right side down underneath. Take out pins before you get near them! Start by lifting the front of the presser foot with your finger and placing fabric and elastic under, then start stitching on and straighten up once the seam is onto the elastic. Dont lift the pressure foot, you just stitch, stop, stretch the elastic to the fullness of the fabric, hold it and seam forward a few inches, then stop and repeat the process. Once right round go over your starting point, then turn and serge off the fabric edge and chain off. Cut, pull the chain to pull it flat and tie a hald hitch in it right up close to fabric. Now turn the elastic band to the inside of the garment. You need to secure it. Usually a straight stitch just onto the lower edge of the elastic with sewing machine from outside.

Have you wound the bobbin with the shiring under tension? you need the shirring elastic to be stretched somewhat as it goes onto the bobbin so that when stitched out, it relaxes and pulls the fabric up.

And yes, usually you need to tighten up the bobbin tension also to stretch the elastic some more.

The Ellure has a horizonal drop in bobbin so you will need to access this to adjust the tension. This may require unscrewing the two screws holding down the needle plate (metal flat plate you sew over). Take this off and now you'll see the bobbin holder area clearly. Look where the tension spring is, the little groove you pull the thread into when threading up. Is there a small dial just near this, about 7mm across? it will have a groove in the top and hopefully a + and - marking.

IMPORTANT: carefully make a note of where it is set now. Take a picture or write a little diagram down so you can get it back to normal setting. Use your little accessory screwdriver and carefully turn it one click to +, then test sew. YOu may need to turn it up 3 clicks to get the elastic stretched enough. Just make sure you know where to set the dial back to when you are done.

Also, remember you won't be able to shir heavy fabric, just light weight cottons work best.

I find that stitching lots of straight lines of shirring like you see tube bodice sundresses made in ready to wear is very hard, factories will have a machine that sews 20 rows at once. And getting enough gathers is trial and error with a domestic sewing machine.

Here's how I do it. Turn down top selvage edge of the fabric width you want to gather, turn down about 10mm and straight stitch around. Now on the wrong side with a sewing marker pen rule lines down from here across the fabric width spaced 1 cm apart. Now lie shirring elastic on these lines and stitch over it with a narrow zig zag stitch making sure not to catch the elastic with the needle. Start each sitching seam one cm from the raw edge of the fabric and finish the seam the same way.

Now I pull the elastic up from each side pulling all of them evenly until I"ve got it gathered enough. Now place right sides together and stitch the fabric into a tube catching the elastic ends in and securing them.

I hope this helps you out.

you are doing it wrong, thread the machine top and bottom as normal, shirring elastic on your lap, select a small zig zag or pattern, sew and as you sew pull the shirring elastic taught, mif you wind the shirring elastic on the bobbin you will mess the tensions up.

Drop the bobbin with the elastic in the holder without feeding it through the holder, and enlarge the stitch length,