Lower Tension Adjusting

My Necchi Lelia was giving me some loose stitches yesterday.  Adjusting the upper tension and presser foot pressure had no effect, so I pulled out the bobbin case and checked the tension on it. I have a spring tool that supposedly tells the proper upper and lower tensions 

but I have used it before and am not happy with the results. 

Tension always seems way too tight after adjusting to the tool's marks. 

I read somewhere on the internet that proper Class 15 bobbin case tension could be found by filling a bag with just under 1 1/2 ounces of sugar and hanging that bag of sugar from the bobbin thread.  Not wanting to keep a bag of sugar around to invite ants, I opted for a bag of metal washers instead.

I broke out my cheap-o balance scale 

and measured out 1 1/2 ounces of washers and put them in a zip-lock bag.

Adjust the tension screw on the bobbin case until the bag of sugar slowly drops. If the bag stays suspended, tension is too tight; if the bag drops like a rock, tension is too loose.  

When you have the adjustment just right, re-insert the bobbin case in the machine and adjust upper tension to achieve a balanced stitch. 

I adjusted the Lelia's bobbin tension until the bag dropped slowly and put the bobbin case back in the machine. Stitches were ALMOST perfect, maybe just a tiny bit tight - I had to increase upper tension to '5' to balance the stitches but it gives me a starting point. I will remove washers from the bag one-by-one until I have a measuring device that gives me the result I want.

My next thought is to use some of that left-over spring wire to make a homemade tension scale.

Ed's Vintage Sewing Machine Shop

Ed