I have a singer 5050c and my stitches are uneven why!?

It will straight stitch but drops one side of zigzag? Could be, in most probable order...

1. Needle is bent
2. Needle not properly inserted into holder
3. Top thread tension to high
4. Top thread uneven feed
5. Hook is bent
6. Hook timing.
7. Needle bar not secure

Here's the manual:

5050 Singer Sewing

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SINGER 5050 Manuals

Singer 5050C Manuals

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first ,re thread the upper bobbin, check the needle to match the fabric and the lower bobbin thread should be the same like the upper thread. If it dose not work, clean the discs tension for the upper thread.

What if you get a thread stand? does it happen when stitching vigorously or normal stitching? Thread stands helps keep tension and avoid thread jumps etc...

here's a free manual & it should show how to set the zig zag stitch

http://www.singerco.com/uploads/download/446_5040_5050.pdf

try adjusting the top tension & see if that helps

Try sewvacdoctor.com and refer to handy problem list. Click on it for answer. Hope this helps.

In your community there must be a sewing machine / vacuum cleaner repair shop. You would be better off going to them to order the part you need then online or over the phone. Singer is a very popular make and it is very possible that this dealer may even stock this item.
In addition to your part, you may benefit in other ways such as bobbins, thread, needles, or other fancy items you can use with your machine. Give it a try, look in your phone book. GOOD LUCK.

Singer manuals are available from their website.

Browse to http://www.singerco.com/accessories/instruction-manuals

and in the search field type in your model number, in this case, 5050, then click "search".

Most manuals are free to download as pdfs.