Well, I am not sure where or what forum this belongs too, but as I figure everybody here sew puppets clothing, you all must know quite a lot about engines.  I got a used singer, looking a lot like the one on this picture. It works very good, but... The thread gets kind of stuck (on the area of the engine I made a red circle) and then breaks!  I tried everything, including some oil. But I have no clue what can it be. Any idea? Thanks a lot! 

I used to have one of these, it is the tension plate getting stuck and catching the thread between the plates.  That particular model does it all the time.  Do you have someone who can service the machine for you?  it needs to be someone who can take the unit out and clean, oil and then reassemble it.

Having said that my mum and I never got ours to work properly and it was serviced at least three times.  Best of luck. 

One other note, make sure that the thread is between the right tension plate and flowing between them freely before threading the rest of the machine.  Also make sure the foot weight is not too high for the material as this will also cause the thread to snap in the tension plates.

It could also be that perhaps yor not threading it quite right.I don't lke singers,I find that they tend to be more trouble than they are worth.Did yo get a manual with it.If not try to find one for you model.The manuals have a trouble shooting guide at the back,you may find an answer there.

Thanks for the advices... I tried again to fix it, no luck. I will get myself another engine....