206rb3 and prewound bobbins

[Oldss72]

Hello - does anyone who uses prewound bobbins on their 206 see tension differences based on the thread diameter? I haven't used prewound bobbins to this point - but just purchased some to try and I notice a tension difference when they are full vs when they are nearly empty. After playing with the bobbin case it seems that maybe as the diameter changes the disk spring force changes.

This wouldn't be an issue with a normal bobbin as the metal would always have the same contact with the disk spring. I was contemplating removing the disk spring and seeing what the result was but I wanted to check with others. It seems that when the prewound bobbin is new the bottom tension is tight and when it is nearly empty the bottom tension is light. 

[MtlBiker]

It sounds like you're not so much talking about thread diameter as the amount of thread left on the bobbin.  Is that right?  But if you really are talking about thread diameter, then yes, it does usually require tension to be reset if you change to a thinner or thicker thread.

I've never used pre-wound bobbin thread either, so I'm following your "thread" with interest.  Are the pre-wounds on a bobbin (surely they must be) that fits into your bobbin case, right?  And if that's so, I can't see that a full bobbin or partially used would need different tension adjustment.  If you wind your own bobbins, doesn't the thread tension remain the same as you use up the thread?  I would be surprised if a prewound bobbin behaved differently.

[Oldss72]

I should have been more clear - for sure I was talking about the amount of thread left on the bobbin. It appears to me that the disk spring that is in the bobbin case creates a drag force on the metal bobbin to ensure it does not continue spinning when sewing stops. A quick google search shows two types of "anti backlash springs". One is an almond shape that seems to touch on the Outside diameter of the bobbin and the other is a C shaped spring with a bump that seems to touch on the center of the bobbin.

My bobbin has the almond shape one. I will be sewing with a normal bobbin tonight since I need another color and I will report back. I might purchase some of the C shaped springs and try those.

[MtlBiker]

6 minutes ago, Oldss72 said:

I should have been more clear - for sure I was talking about the amount of thread left on the bobbin. It appears to me that the disk spring that is in the bobbin case creates a drag force on the metal bobbin to ensure it does not continue spinning when sewing stops. A quick google search shows two types of "anti backlash springs". One is an almond shape that seems to touch on the Outside diameter of the bobbin and the other is a C shaped spring with a bump that seems to touch on the center of the bobbin.

My bobbin has the almond shape one. I will be sewing with a normal bobbin tonight since I need another color and I will report back. I might purchase some of the C shaped springs and try those.

Good luck!  I'm looking forward to your report.  I'd been thinking of trying some prewound bobbins, but not if I'm also going to have to change the spring on my bobbin case.  If you hadn't reported this, I would have expected transparent interchangeability between prewound and self-wound bobbins.

[RockyAussie]

For what its worth I have found on most of my machines that when the bobbin is below 1/4 full and I am sewing light stuff I have to turn the top tension down to compensate. This is on the metal ones. Normally I go back about 1/4 to 1/2 a turn. backlash springs may help but the direction the bobbin is loaded in the clockwise or anti clockwise will make a fair difference as well sometimes.

[ljk]

Time to comment. I've had a 206 since 1976.  Here's my experience with bobbins.  The spring you talk about tends to provide some side load. If you have a needle break it can hit the case and bend it'.   I've no back lash problems,  I do upholstery and leather, speed is not my friend.  For high speed on my commercial embroidery machines I use magnetic bobbins exclusively. Watch how tight you wind your bobbin,  This can warp the sides.  It will still insert but will turn uneven.  Bobbin cases can warp. There cheap now, not 45 years ago.  Pay attention to your bobbin, blow out lint especially the tension spring. Make sure your 206 is timed correctly and the bobbin case is not touching the hook. If it is you may not hear it and that needle can simply tap away doing  doing damage.  FIL-TEC magnetic bobbins are available  on-line.

[Sculptor]

I have just acquired a vintage, Singer 236g120 for leather work....the gal threw in a bag of pre wound bobbins which I am going to use as she said that is what she used...looks like the are a "g" bobbin. I do not know where to purchase them, but believe she said I could get them at JoAnn Fabric.???I also have some of her thread she used,,#69 nylon which is old, dusty and sticky...I will NOT be using that as it is hard to pull through after threading the machine....I can' t imagine that being friendly to my tension? Anyway, I am also looking for a new belt for the upper Roller pressure driving belt......any suggestions on where to get parts would be great Thanks!

[kgg]

2 hours ago, Sculptor said:

I do not know where to purchase them, but believe she said I could get them at JoAnn Fabric.???

You can get them from American & Efird directly or Wawak ( https://www.wawak.com/Thread/Thread-By-Use/Bobbin/redi-wound-nylon-style-g-bobbins-144-bobbinsbox/?sku=THD122WH ) at about $38 US for 144 in a box.

kgg