Cobra class 26 thread tension knobs/adjustments

[DieselTech]

Guys & gals I finally got my cobra class 26 up & running. 

I have a question regarding the thread tension knobs. 

I watched Al Bane thread tension adjustment video & I can't tell in the video which knob he is adjusting. There is 3 knobs. 

I think he adjusted the big black knob in the center. 

My top thread is looping on the bottom, telling me to tighten my top tension. 

Can somebody tell me which knob to adjust 1st? 

Also the silver knob is completely loose. What does it control. Is that some type of fine thread tension adjustment? 

Should the silver knob have some tension on the spring that is behind it? 

Thanks any & all help will be greatly appreciated.  

[DieselTech]

Ok guys & gals I believe I got it straighten out. 

138 bonded nylon

Size 22 or 23 needle. I have not verified needle size. 

1.02mm chrome tan upolstery leather folded over & sewn. 

I believe for testing purposes on this thin of leather I got it as good as it can get for my given thread, needle, & leather selection. 

To correct thread tension from out of the box. I tighten silver knob 1/2 turn. 

Then i tighten black know a touch less that a 1/2 turn. 

Here is couple pics of stitching. 

[DieselTech]

In the 1st set of pictures on the 2nd Pic, that is the leather puckering on the back. 

Believe that is due to presser foot tension too high. 

So here is a couple more pics of the same piece of leather in different lighting. 

[Constabulary]

3 hours ago, DieselTech said:

138 bonded nylon

Size 22 or 23 needle. I have not verified needle size. 

Sorry to say that but needle size matters!!!! Otherwise playing with the tension does not make much sense.

If the 2nd picture shows the underside then I would guess your needle size is too small meaning the needle hole is not large enough so the thread knot cannot be pulled into the material.

Thread tension is no science you don´t need markings you just have to understand how top and bottom tension plays together (mentioned in all proper sewing machine manuals) and again you have to use the right needle size. Even when a needle thread chart tells you what the "right needle" is in reality it can be slightly different.

BTW the lower nut with the marking at 3 o clock has nothing to do with tension.

The silver nut on the right (marking at 10 o clock) is just a light pre tension but the main tension unit is the nut with the marking at 1 o clock this is where you adjust the top thread tension in general.

Edited September 21 by Constabulary

[DieselTech]

3 hours ago, Constabulary said:

Sorry to say that but needle size matters!!!! Otherwise playing with the tension does not make much sense.

If the 2nd picture shows the underside then I would guess your needle size is too small meaning the needle hole is not large enough so the thread knot cannot be pulled into the material.

Thread tension is no science you don´t need markings you just have to understand how top and bottom tension plays together (mentioned in all proper sewing machine manuals) and again you have to use the right needle size. Even when a needle thread chart tells you what the "right needle" is in reality it can be slightly different.

BTW the lower nut with the marking at 3 o clock has nothing to do with tension.

The silver nut on the right (marking at 10 o clock) is just a light pre tension but the main tension unit is the nut with the marking at 1 o clock this is where you adjust the top thread tension in general.

Thanks. Yeah nobody mentions in vids what the other 2 knobs are called & actually does/controls. The silver knob & black knob on bottom left that is. 

[AlZilla]

33 minutes ago, DieselTech said:

Thanks. Yeah nobody mentions in vids what the other 2 knobs are called & actually does/controls. The silver knob & black knob on bottom left that is. 

The knob on the right, as mentioned, is a little pretension (which I suspected but kept quiet until it was confirmed). The bottom is to set your take up spring. That part I know because it looks a lot like a Singer 111 type of tension unit. The biggest difference I see is that pre-tension gizmo on the right - the Singer (and others) unit has a little flag with 3 holes to accomplish the same task.

That take-up spring can cause you trouble if it's not just right, too. On any sewing machine. It's worth double checking.

Have you tried it out on thicker leather? I thought Cobra had a pretty good reputation for sending their machines ready to sew.

Edited September 21 by AlZilla

[DieselTech]

30 minutes ago, AlZilla said:

The knob on the right, as mentioned, is a little pretension (which I suspected but kept quiet until it was confirmed). The bottom is to set your take up spring. That part I know because it looks a lot like a Singer 111 type of tension unit. The biggest difference I see is that pre-tension gizmo on the right - the Singer (and others) unit has a little flag with 3 holes to accomplish the same task.

That take-up spring can cause you trouble if it's not just right, too. On any sewing machine. It's worth double checking.

Have you tried it out on thicker leather? I thought Cobra had a pretty good reputation for sending their machines ready to sew.

Thanks AlZilla. When I got the sewing machine out of the box, the top thread was looping on the bottom of the leather.  Did not matter if it was thick or thin leather at that time. 

I'm not sure if the upper tension knob backed off while in shipping.

Or it was from thread routing thru the pin on top of the machine. I suspect if I was to wrap the thread around it & go thru multiple holes on it. It might have corrected my thread tension. 

Edited September 21 by DieselTech