Most transverse shuttle machines take 12×1 or 13×1 needles which were standard at the time but are unfortunately no longer made. Many people have searched for a modern substitute, and many solutions were found, yet every time I had such a machine in my sewing room, nothing would fit. The reason for it is that there is no modern needle with the same measurements.
Old 12×1 and 13×1 needles had a thin shaft at the top where it goes into the needle clamp. Both types had the same diametre but 13×1 needles were longer. So the needle clamps were designed to take a 1mm thick needle, whereas modern needles start with 1.6mm thickness at the top. (Yes, I know about NBx5 which are thin at the top, but trouble is, they are not available in useful sizes. Size 50 is way too fine, and even in this size these needles are hard to impossible to find.)
Having fiddled with substitute needles for several 12×1 and 13×1 machines, I realised that different makes had different designs of the needle clamp. In some cases you could actually use a thicker needle! What a relief.
My 1885 Wertheim TS is one of the lucky few.
It has a groove in the needle bar and a flat needle clamp that opens wide enough to take a thicker needle than the 12×1.
So I was able to use an industrial 108×3 needle instead! 😃
Once I cleaned out the groove and the needle clamp properly 😉, I found that the needle aligned very well both with the needle hole and with the foot. What luck!
This needle has the same diametre as a more common industrial DBx1 needle, but it is longer. Indeed, I started by fitting DBx1, but it wouldn’t pick up the thread – clearly, this Wertheim TS was designed to use the longer 13×1 needles. So 108×3 did the trick as a substitute.
If you find that the needle doesn’t align very well in your machine, try loosening slightly the screws that hold together the head. This will introduce a little play into the movement of the needle bar. Watch it carefully though – it might help or it might make things worse. It seems that depends on the individual machine, how it’s been used and how it aged. After all, it’s over 130 years old!
See also this post on selecting substitute needles.