Hello Donna,
There are two types of 630, one with a self wind bobbin and one with seperate bobbin, if you have a self wind bobbin there is no adjustment, the only thing you can try is to wind the bobbin with the presser foot down instead of up, if you have the seperate bobbin winder you need to take the bottom off the machine and adjust the bobbin winder pretension by undoing the screw and moving it slightly.
drivewithken, August 2009
