greywuuf,
Yes it does make sense. Somewhere, and I don't remember where, in one of the manuals I saw the spec of .020" for clearance between the spring and hook in a machine with a Class 15 bobbin. This came about because the little spring in the bobbin / hook area in my MW 7 Jewell had been bent to zero clearance and the tension was alllllllll messed up. Birds nests of mega proportions. I took it all apart and straightened it till there was some clearance and all is well again.
I wonder if this could be the cause for the noise in the later Singers with the horizontal drop in bobbins? I've got 5 of them that clatter and tinkle in that area. Hmmmmm, something to check.
Joe