Vertical oscillating hook is based on Singer 15 which was originally a side-facing straight stitch hook.
It is now perhaps more familiar as a forward-facing hook in many domestic machines. There is even a rotary hook derived from it, one variant is found in Husqvarna Viking machines from 1950s, another in Janome machines from 1970s, and there must be more, I’m sure.
The vertical oscillating hook is a removable hook that is pushed about the race by a driver – either a solid steel one or one covered with a spring. Either way, there is a gap between the hook and the driver through which thread must pass as the loop goes around the bobbin case. The size of this gap greatly influences the timing of the hook and the type of thread that can be used on the needle.
Removable hooks have a bit of “play” in them because the hook can wobble in its cradle. But the oscillating hook is special: the need to have this gap between the hook and the driver also allows for an instant adjustment of timing without turning any screws. The rotary hook, although similar and removable, does not offer this option!
So our dear familiar and well and truly domesticated vertical oscillating hook secretly offers an absolutely wild possibility to have a collection of slightly different hooks to be used with different and often forbidden thread weights and needle sizes without any change to the timing setting. Just swapping over the hook can also instantly transform your medium-tensioned machine into a low tension or a high tension one for special applications like sewing coats and jersey (low tension) or puffed quilting and heavy duty work (high tension). What madness! 😵
The downside is that you have to be very careful to select the right hook for the project and you have to maintain the race and the springs in it meticulously for the hooks to work as expected. Lesser quality machines often have a less precisely manufactured hook, and combined with less precise assembly and adjustment at the factory, such machines turn into a lottery – how many stitches will it skip today?
Not all hooks are born equal
Of course, the hooks from different manufacturers are all very slightly different but not labelled as such – that would have been too easy. But you can measure the gap between the butt of the hook and the end of the driver (or its spring). There can be quite a difference!
For example, my 1955 Haid & Neu Primatic is a forward-facing vertical oscillator manufactured to very precise specifications.
It has its timing set at the factory with pins instead of screws, so it cannot be knocked off but also it cannot be adjusted. It usually works fantastically well with its own native hook. However, if I want to use a thicker thread with a twin needle to do bold satin stitch embroidery, it gets a bit too thick and starts jamming the hook. Well, I’ve been buying various hooks from different machines and have quite a few of them in my draw. They are all supposed to be identical, but of course they are not. When inserted into the race of my Primatic, the difference is clearly visible. The maker’s name or logo is engraved inside the hook.
Why do the Jaguar and Janome hooks leave such large gaps? Because the driver spring in those machines is shaped differently. Here is a Jaguar hook, notice the spring curl at the butt end.
The hook action in one of these machines is quite different from the original Singer. The fit can be made tighter than in the original because the spring can be depressed to make extra room. These hooks can also be quieter than springless hooks. In my experience however the original Singer 15 machines – with or without the spring – still win in stitch quality simply due to the superior quality of manufacture of Singer machines. The springless hook may be a bit louder because a larger gap is needed in this design, but my 1920 Singer 15K sews an impeccable stitch on a wider variety of fabrics than any less well made machine with a fancy spring in its hook.
Some makes use positioning screws rather than permanent pins to set the timing of the hook. Such hooks often slip when you get a thread jam or try to sew material that is too thick. This is annoying because you’ve got to reset the timing to get it to work again. On the up side however, you can play around with such machines and set the timing to work with the hooks in your collection. There’s a silver lining everywhere. 😁
The hook affecting tension
The title here should rather be: swapping the hook for the one more suitable for the type of thread and fabric allows to keep the tension unchanged between projects. But that’s a bit long for a title. 🙂
Normally when you switch between significantly different fabrics or types of thread, you need to re-balance the tensions, or at least adjust the upper tension. I noticed however that using a different hook can produce a balanced stitch without touching the tension knobs. I tried to come up with a general rule or a full explanation, but it seems that there are many factors at play here, so it is not straightforward. However, in most cases use a tighter fitting hook with fine materials and thin threads, and a looser fitting hook with heavier materials and thicker threads.