Bobbin case i am looking for a bobbin case to buy 'coz i lost mine. i ordered from the internet but they gave me an apollo spool bobbin case instead. i looked at my machine but i saw a similar type of thing inside, so i do not know whether i bought the right one , the last time i remembered i use my machine i have to put the bobbin into a metal bobbin case before putting it inside the machine. please help me. i haven't use my machine for a long time and i badly need to use it now

Can be several causes. In typical probable order for rotary hook machines;
1.Top thread tension is too high (lower tension)
2.Top thread snagging at spool or elsewhere (for hoizontal spool use larger spool cap and/or machine not threaded per specific instructions)
3.Bent needle or barbed needle point (replace needle)
4.Needle not properly inserted into holder (see specific machine instructions)
5.Debris in shuttle hook/race (clean bobbin, hook, race)
6.Wrong bobbin (replace with proper machine bobbin)
7.Bobbin thread tension too high (reduce bobbin spring pressure, likewise top thread tension)
8.Poor quality or extremely light thread (if using cotton only thread, test sew with a polyester blend and see if problem goes away)
9.Bobbin case (replace bobbin case)
10.Machine timing. (check/adjust timing)
11.Burr in hook race, this can happen if a broken needle point jams in the race (remove burr or replace race)
12.Machine timing. (adjust timing)
13.Hook is worn or damaged (typically not a worn hook unless a few hundred hours of use, look for a barbed or bent hook point) Watch following Singer video... see testing top thread tension.
https://www.youtube.com/watch?v=O7N4XaIV6ms
and following animation on generic rotary hook sewing https://www.youtube.com/watch?v=zqRvljnNLFk

http://www.sewingpartsonline.com/singer-5040-sewing-machine-parts.aspx

SingerOnline com Apollo Bobbin case installation

Amazon com Singer Bobbin Case

Here is a selection:

Sewing Machine Parts Singer Parts Singer 400 The Sewing Outlet

The singer 543 uses an Apollo bobbin case. pictures here. Bobbin Case Apollo Dressmaker Singer 421326

http://www.amazon.com/s/?ie=UTF8&keywords=bobbin+cases&tag=googhydr-20&index=aps&hvadid=10737056677&hvpos=1t1&hvexid=&hvnetw=g&hvrand=15006756111784313817&hvpone=&hvptwo=&hvqmt=b&ref=pd_sl_6l6kc3ei5l_b

I think this is your bobbin case
http://www.sewingpartsonline.com/bobbin-case-apollo-singer-421326.aspx
being plastic they are damagable if the case moves and the needle strikes it. Sometimes you can file out the damage with a nail file. But replacements are available too.

Hope this helps.

The shuttle hook is suppose to hook the needle (spool) thread and loops it around the bobbin case to form the lock stitch. Is it possible that something was adjusted without proper clearances as to allow the thread looping around the bobbin case to do so without catching up where it should pass through freely?
~<Ray>~

remove bobbin; remove spool; look on side of bobbin case for a tiny screw (bobbin tension) adjust screw untill top and, bottom thread lock is the same

I solved this problem by buying a new Apollo Singer bobbin. It was $12.00 at a local sewing machine store. This bobbin is everywhere, since it goes with about 30 Singer sewing machine models.

I had to do a little adjusting to the new bobbin. 1/3 of a turn loosening the tiny screws.

You can order one online, I am not sure about shipping costs.
http://www.vacsew.com/vacuum/singer-apollo-bobbin-case.html?printable=Y
I jsut bought one for $15 at my local sewing store.