While cooking has become less-frequent-to-do than build things for me, it still burns my biscuits when the only reasonably priced (i.e. under $2 each) potholders are so thin and poorly made that the heat burns right through in the moments it takes to move a pan from the oven to the stove-top. And to find a decent potholder at any price that doesn't look like a piece of modern art or a chicken is just impossible as far as I have found. Not that I have any thing against modern art or chickens... I just don't care for them in my soft sage-green and wood kitchen. The best I was able to do so far was some sage-green on one side and bright blue on the other that were mediocre in heat protection, or black silicone ones that look great but don't protect from heat at all.
So I finally decided if I could find some plain cheap ones at the dollar store that were not a bad color, then I would sew two or three together to make a better one. What I found instead was these perfect colored place-mats made from woven cords of cotton material and one of my better ideas struck me... the woven cords would make much better heat protection than normal potholders with thin cotton shells and thin batting inside...
and with a few folds the place-mats would be several times thicker and about the right size for potholders.
I picked out four that were the same color (harder to do at the dollar store than you might think) and brought them home. After playing around with several different ways to fold them for size and thickness, I chose a three fold on the long direction and a single fold from the short direction.
My first attempt at sewing them looked okay from the top, but the thread was bunching on the bottom terribly.
After a lot of colorful language, threatening the machine with defenestration, and re-threading the sewing machine a dozen times with different tensions, which is the only recommendation for fixing the problem I could find on the internet, I started running a single stitch at a time and checking the bobbin area after each to see what the problem was... and found it.
( Just to note... this is a Singer Sewing Machine, so these steps may not work for your type. )
First, try the recommended re-threading of the machine with the presser foot up and trying different tensions on the top thread. However, if your problem is clearly that the bobbin carriage (the whole area that the bobbin holder goes into, not just the bobbin holder itself) is getting pulled out of place and wedging tight in the brackets that hold it, then re-threading isn't going to do much good.
This is what was happening with my machine. The thread was pulling the bobbin carriage up and jamming in place causing all subsequent threads to jam on top of the original jammed thread until it either got knocked loose by another thread or I pushed it back down.
IF this is the problem you are having, unscrew the cover plate and remove it.
Try cleaning any dust and lint out of the machine to see if that is what is causing the jams.
If that does not fix the problem and IF your machine looks like this, then loosen the two screws indicated and slide the plate to the left to better secure the bobbin carriage in place. It should keep the bobbin carriage from getting pulled up and wedged in the machine, but no so tight that it prevents the top thread from easily sliding around the carriage. I had to adjust it twice to really get a good fit.
Especially since every brand and model of sewing machine is a bit different, I can't at all say this would work for your machine, but it was cheaper than taking it to a repair shop and worked for me.
And so... after a 10 minute project turned into a four-hour ordeal, I have some nice quality potholders that are thicker, stronger, and prettier than expensive store bought ones.
All for $1 each... and a chunk of my sanity.
And now all I need to do is find half a dozen more that match at the dollar store so that I never have to hunt for a decent potholder again.