tropit

I got my Singer 403A the other day after bidding on it on EBAY. It's in beautiful shape and looks practically brand new. It was moving pretty stiff, so I oiled and greased it thoroughly, removed the bobbin case and cleaned out the bobbin area and applied more oil. There was hardly any lint in it...it looked pretty clean. It runs much smoother now, however, it's still sounding a little rough in the bobbin area and is making a minor grinding noise. It sounds like the noise is coming from under the feed dog, perhaps hitting a rough spot when the hook makes a complete rotation. I have another 403A that I've had for ages, so I'm pretty familiar with this machine, but I've never ventured to take apart the entire bobbin area. Do I need to? Tips please...thanks so much.

~ Cindy