If you watch the video carefully you'll see that it's tightened before needle insertion.

@@3FTERS It is tightened at 35 sec ending at 37 sec. and it appears tight but it's not. At 39 sec. the needle clamp is loosened so the needle can be inserted and that screw on the left becomes loose again. The needle clamp screw was holding tension and when that tension was released the screw becomes loose again. Watching the video from the 39 sec point onward, until she tightens the needle clamp screw at about 49 sec., every time she bumps the needle clamp you can see that the screw on the left is not tight. When that screw is tight the needle camp doesn't move around. I always tighten that screw when the needle clamp screw is loose so I know that it is tight, not just acting like it's tight. Don't take my word for it. Check it out for yourself, you will find that I am correct. That screw on the left was never tightened properly and you don't want to have that screw come loose and fall out. It is too easy to lose.

Hello, the 300 series along with the earlier 206 that take 15x1 are not newer but different models than those that take the short needles. Probably destined for different markets. It's not just the bobbin case that's different but the hook assembly with a small difference in how it grabs to the axle. As you said, you can remedy the case in order to use 15x1 needles but that doesn't fix it all 100%. You can stitch but the tuning extremities of the machine can't be reached. But it's an easy fix nevertheless so that you are not held prisoner of the short needles which are so hard to find and in very few types and sizes.

@@3FTERS Whether open top bobbin case or closed top bobbin case with the slot for the pin at the 5 O'clock position on the bobbin case base, it is the width of the half moon cutout area that allows for the longer 15x1 needle. Some of the closed top bobbin cases, with the slot for the pin at 5 O'clock on the bobbin case base (bobbin basket), or the open top bobbin cases (with the two pins near the top of the bobbin case base) have wider half moon areas. That is all that is needed. A wider half moon area. You said "but the tuning extremities of the machine can't be reached". I have no idea what you are referring to. Once the half moon area is widened these machine sew perfectly with a 15x1 needle in all respects.

@@treperrys The 320 of the video is a 15x1 model by the factory (SINGER) and has a different hook assembly (different part number) which attaches differently on the rotary axle than the hook assy of the the 320 designed for short needles. They may look the same but they are different models although they are designated with the same model. It's not a DIY conversion we've made. The bobbin case is standard and not modified. The same goes for the 318 and other 300 series. Also there are SINGER 206 that take 15x1 while at the same time other 206 take the short needles. The two different 206 models also have different hook assemblies. Since 206 and 300 series were made in 2 different versions and since the 206 is a predecessor of the 300 series, i guess it's safe to assume that they were destined for different markets. It's not about earlier or later since both series came with both needle systems but with years apart. The problem with the 206 and the 300 series arise by the fact that you can't know which take what needles just by looking at them. Also the bobbin cases on a machine are not indicative of what needles this machine take because with years their bobbin cases might have been replaced. You need to go and check the hook assembly and even then few people have the opportunity to have both models so they can spot the difference and even then it's not an easy task to do. There's a big misconception that 300 series have that issue and need to have the bobbin case grind when not all of them need that.

@@3FTERS Are you talking about the hook assembly that uses the open top bobbin case vs. the hook assembly that uses the closed top bobbin case? Is any of this mentioned in the manual? That is, do any of the manuals (except for the 206) say you can use the 15x1?

Very true...

I have a singer AC 206234 on my margetplace Mike Watt

www.etsy.com/listing/529581901