singer 7 class bobbin thread tension

[desertskies]

I am a parachute rigger in Az and have a Singer 733 I use for harness work. I need a tighter bobbin thread but tightening the tension screw has no affect. Looking at the bobbin casing as I insert thew bobbin, run the thread through the tensioner it then is routed to a hole in the tensioning spring which provides no resistance at all so tightening the tensioner is useless. I've had this machine foe several years and its never been an issue, if I ever had tension issues it was usually with the. needle thread which is easier to address. Not sure what I need to do. If I loosen the needle thread to get the lock stitch in the middle I will have too loose a stitch so it seems to me I need a tighter bobbin thread but the tensioner seems to have no effect on the bobbin thread tension. 

 

Thanks for any help

 

JHL

 

 

[shoepatcher]

Try replacing the bobbin tension spring with a new tension spring.  Make sure the old spring does not have a groove worn in the back of the spring.

glenn