Manual for brother ls-1217 sewing machine

not sure if this link will help you but have a look.
brother LS 1217 Tension control knob locked in position Google Search

Are you sure that it's a Singer LS-1217? I can't find any model with 1217 on the Singer site.

The Brother LS-1217 manual is available here: http://welcome.solutions.brother.com/bsc/public/eu/eu_ot/en/doc/manual_top.html?reg=eu&c=eu_ot&lang=en&prod=hf_ls1217euk . The direct link to the English version of the manual is http://download.brother.com/welcome/doch000000/ls12171217b13171417ug01enesfrpt.pdf . There are only a few knobs on most machines. On the front near the needle is the Needle Thread Tension knob. If you use contrasting colors (different top, bobbin and fabric colors), you might see a straight stitch where the top thread is visible on the bottom of the fabric for example. Adjust the tension to get both the top and bobbin threads meeting in the middle of the fabric layers. (Increase the needle thread tension - rotate to a higher number but go in 0.5 increments.)

Then you have near the motor area the stitch width and length knobs. The width is only for zigzag stitches. A long stitch length is good for a temporary seam (like basting in a zipper or hem) before you finish that area. However, the width and length should be adjusted depending on the fabric. A fine fabric needs a smaller stitch, usually. The knob on the right side of the machine is the balance wheel (or hand wheel). This adjusts the needle height so that you can have the needle out of the way while changing the bobbin, for example.

I hope this helps.

Cindy Wells
(I use the Singer Sewing Book as a reference for tension issues.)

hi Patricia.
It could be the needle, the tension too tight, mis-threading, the thread weight.
try these links out and see if it helps you.
Sewing Machine Problem 1 Thread Breakage
Sewing Machine Thread Keeps Breaking
Why Does My Thread Keep Breaking While Sew
FAQs Troubleshooting LS 1217 Others Brother
Brother LS 1217 Mechanical Sewing Machine upper thread keeps on breaking...

http://www.retrevo.com/support/Brother-LS-1217-manual/id/19095bh739/t/2/
above is your manual so you can learn how and what to do...

Brother does not provide a good description of the knob. Often times the knob is actually a nut and you can screw it back on. I have a feeling you might have a cheap, ready to break at any moment, machine. If you get a new machine, focus upon metal.

You should be able to fix this. IF it is the top thread on your fabric that is screwy you need to adjust the bobbin tension.
If it is the bottom thread you have a problem with your upper tension. Blow out the upper tension assembly using canned air, the tension discs may be dirty

Sally, Here is a link to Brother LS-1217 Quick Setup Guide and Users Manual. Hope this will satisfy your needs.

A mass of loose thread on the bottom of the fabric most likely indicates a total loss of upper tension. Remove the upper thread, raise the presser foot and rethread the machine. Make sure that the upper tension knob/dial is around 5. If you still have a problem, let me know what brand and model you have.

If you contact you local Brother retailer and explain the problem and give your model number they ought to be able to order a replacement which you can install yourself, or, probably more prudent, ask them if they will do it and also check for any other associated "modifications" made by the little fellow.

USA Dealer Search

or.......There ought to be one similar in your home country

www.brother-usa.com you can download a manual for free there I just did