When my needle goes down into where bobbin is held,the needle hits the bobbin case.

SOURCE: Bobbin Case Spins - in Huskystar C20

I had this problem when I first bought my machine. I took it in and they told me it was a recall problem. All the machines were having the same problem. They fixed it and I have not had the problem since. I bought mine at a Joanne fabrics. Hope this helps.

SOURCE: needle hitting bobbin case model 750

This is a timing problem the hook timing needs adjustment, and possible the needle timing also

SOURCE: needle hits bobbin case...

If the needle hits the bobbin case the are only 2 things that could be wrong. Lets hope its the easy one, there are more than one length of needles, if the needle is to long or it is not all the way up in the neelde bar, the needle will hit the inside of the bobbin case. Now if that is not the problem then the machine is out of time. ALWAYS check the easy stuff FIRST.

SOURCE: The thread is bunching up

Your problem stems from the faulty foot lever mechanism. It's coupled to the upper thread tension control which only provides tension when the presser foot is in the locked down position.

If the presser foot won't positively engage in the down position, there's no upper thread tension and the thread bunches up below. Everything else stems from there. If the needle has hit the bobbin case too frequently then the bobbin timing may also be slightly out and the needle itself will be damaged and won't pass straight through the fabric; it only takes a tiny deflection from the vertical as it passes through the workpiece for the needle to flex and hit the bobbin case.

In summary, your machine is in desperate need of repair and adjustment. You haven't stated which exact Singer model you have, but they are usually easy to get servicing manuals for or you can take the machine to a sewing machine servicing specialist. Most singer spare parts (even for 100 year old machines) are usually still available fairly cheaply from a variety of sources, just enter "Singer spares" into your search engine to find suppliers.

To prevent re-occurrence, clean the mechanism regularly and lubricate it as directed by the manufacturer using sewing machine oil. Depending on how often you use the machine, do (or have done) a more thorough service periodically to check the timing and also that all mechanism screws remain tightly fastened.

I hope that my reply has shed some light on your problem and enables you to decide what to do next. Please take a moment to rate my answer.

SOURCE: Needle breaking, hitting bobbin case

I had this problem and it is very easy to fix!
With mine I looked at it for about half an hour, and all I needed to do was put the bobbin case back in,(how it fits normally) and then hold it and turn it anti clockwise until it clicks, it may be quite pressured to do but ive heard a lot of people having this problem and thats all that needed doing!
Hope i helped! :)