Cobra Class 26 bobbin tension test

[fernwehleather]

Hello,

Does anyone know how to do a bobbin tension test on a cobra class 26 sewing machine since you can’t take the bobbin apparatus out (that I’m aware of…)?

thank you,

[RockyAussie]

Curious to see other answers on this myself. From me....put your top tension knob adjuster mid ways through its length of travel. Probably 5 turns in from fully loose. AS long as you have the right needle and thread combination then load your bobbin in and stitch a piece of leather 1 to 2mm thick (3 to 5 oz) a couple of inches. If the knots are showing on top tighten the bobbin spring about a 1/4 turn at a time until the knots are centred. If the knots are at the bottom then loosen the bobbin spring about a 1/4 turn at a time until the knots are centred. This method should mean that thereafter you only need to tighten or loosen the top tension for any adjustments unless you are going right from the thinnest to the thickest threads in your changeover. Hope that helps.

[fernwehleather]

Thank you RockyAussie. This sounds like a good test to try. Just for clarification, when you say “5 turns”, do you mean a full 5 turns? Versus half a turn, etc…

[Northmount]

Moved to Leather Sewing Machines

[RockyAussie]

9 hours ago, fernwehleather said:

Thank you RockyAussie. This sounds like a good test to try. Just for clarification, when you say “5 turns”, do you mean a full 5 turns? Versus half a turn, etc…

The turns in from loose would be best found by counting how many full revolutions there are from fully loose to fully tight then turning the knob to be half way. This gives you plenty of room to tighten or slacken the top thread tension without needing the spring to be over tight or over loose between various thread changes or job thickness and firmness changes. 

[fernwehleather]

Got it, thanks!