The Difference Between Class 15 and 15J Bobbins and Why You Should NOT Use Them Interchangeably
Backstory
For the past week I've been reattaching all my photos to each of my posts on some of my blogs due to losing all my photos when I deleted my main account (read about it here.) I ran across the Singer sewing machine reviews that I had done--mainly the Singer 9960 Quantum Stylist--my all-time FAVORITE sewing machine! I had sold it (along with my Futura XL-400) 5 years ago and purchased a Singer Futura XL-580 instead. (I figured I could sell two machines and just use one, so I wouldn't be using up so much space in my bedroom.)
Since the day I sold it, I've regretted it. I loved that machine. A while back when I had checked to see if they still made them, I found it had been discontinued. I was just curious so I looked again and was surprised that they started making them again! On sale for $500 on singer.com. So since I had sold mine on facebook marketplace years ago, I was just curious if someone was selling theirs. Sure enough, I found one that was used only once and they were selling for $250. I jumped on the deal. I was so happy and excited to get my baby back!
What happens if you use 15J bobbins in a machine that takes class 15?
The Singer 9960 takes class 15 bobbins, while the Futura XL-580 takes 15J bobbins. When I had my old 9960, I also had the Singer Futura XL-400. I didn't think the bobbins were different, so I used them interchangeably. They seemed to work fine for both machines. However, I ended up having to replace the bobbin case in my 9960, which was $100 to replace! That's a huge expenditure for a machine that costs $500-- a fifth of the price of the machine, just for using the wrong bobbins. The XL-400 bobbin case is $23 to replace and I had purchased one at the same time I purchased my replacement case for the 9960, just in case it broke, too. I don't know why such a huge price difference.
At the time, I hadn't realized that the bobbin case broke because I was using the wrong bobbins. I also had to get the timing reset at a repair shop. Had I known then what I know now, it would have saved me a lot of money. The singer website has answers that specifically say what happens if you use the wrong bobbin.
What's the Difference Between Class 15 and 15J Bobbins?
The singer website has a resource page describing what the differences are in the bobbins. However, they look identical to me! It's so hard to tell the difference on this page. They are only 1mm difference in size. So, I went ahead and purchased bobbins at Walmart, since that was the cheapest place to buy them. I purchased both kinds so that I can see what the difference is, so that I can tell which ones I currently have.
When purchased in a pack of 4, they have a raised center and square hole. I don't think all of them have the raised top and bottom. The singer website shows one without a raised top and bottom. 15J bobbins in a package of 3 do not have a blue tint like the singer website says.
Since I can't rely on my eyes to tell the difference, I decided to purchase a caliper to measure them. I bought one at Harbor Freight for $1.99. As you can see in the photos below, the 15J is just a hair bigger than the 15. (You may need a magnifying glass to see.)
