In part 1, I covered feed dogs, needle plates and adjustable presser foot pressure. Here's the link to last week's article in case you missed it. Today I'll be diving in to hooks and motors.
Hook Type
The two most common hook types are rotary hooks and oscillating hooks. You may also come across CB hooks which are basically Bernina's own vertical oscillating hook system. Rotary hooks spin around 360 degrees while oscillating hooks rotate about 200 degrees before doubling back on itself and never complete a full rotation. Early rotary hook systems made one rotation before grabbing the thread, while newer systems make two full rotations before grabbing the thread. For the vast majority of people, there is no practical difference. As a rule of thumb, rotary hooks are capable of achieving much higher top speeds because there is minimal resistance on the hook when spinning all the way around. Oscillating hooks on the other hand, need to reverse momentum with each oscillation, thereby introducing a ton more resistance and vibration.
This resistance equates extra strain on the mechanism which in turn caps the maximum theoretical speed at about 1600 stitches per minute. Seeing as most domestic machines top out at about 1000 stitches per minute (there are a few exceptions) we don't even come close to a high enough speed for the hook type to matter. Industrial lockstitch sewing machines, on the other hand, are an entirely different story and almost exclusively use rotary hooks where the theoretical maximum top speed is virtually limitless. It is not uncommon for an industrial straight stitcher to sew at 5500 or more stitches per minute!
Back to domestics, I generally find rotary hooks slightly quieter and slightly smoother but the difference is really only noticeable at higher speeds.
Horizontal vs Vertical Hooks
In my reviews, I often refer to machines as horizontal or vertical hook machines to describe the orientation the hook sits at. It's worth noting, whether a machine has a horizontal or vertical hook is completely independent of the hook type. You can have horizontal rotary hooks or horizontal oscillating hooks. The same goes for vertical hooks. Having a horizontal hook however, does mean the bobbin must load from the top of the machine bed, while vertical hooks can potentially load from the front, side or rear of the machine.
Side loading, vertical rotary hook
Top loading, horizontal rotary hook.
Top loading, horizontal rotary hook.
In horizontal rotary hook machines, the hook is either located in front, to the side of, or behind the needle hole. All of these configurations are considered top loading, regardless of orientation.
Front load, vertical oscillating hook.
Front loading, vertical, rotary hook.
Rear loading, vertical, rotary hook.
So what are the practical advantages of each type? Truth be told, most of this boils down to personal preference, I know some sewers who prefer the top loading, drop in bobbins because they are easier to see and access. Others, prefer loading the bobbin from beneath the bed of the machine because this means you can change the bobbin without removing your fabric from under the presser foot.
Bernina front loading oscillating hook
Elna top loading rotary hook
Non top loading machines are generally easier to clean as there is easy access to the hook and race. Top loading Elna rotary hooks, on the other hand, are considerably more difficult to access for cleaning.
Minor differences aside, there is one compelling reason to choose one hook over another. Side loading machines (and single bobbin top loaders with the hook to side of the needle hole), cannot accommodate twin needle sewing. Modeled after the original Singer 15-91, many zigzag capable class 15 clones thread from side to side. I won't go into how stitches are formed in this article, but just understand that the hook needs to pass behind the scarf of the needle in order to grab the upper thread. Given this configuration, it would be impossible for the hook to reach a second needle. Keep this in mind if you plan to do any twin needle sewing.
External vs. Internal Motor
Domestic machines can feature internal motors or external motors. External motors are nearly always belt driven while internal motors can be either gear or belt driven. Internal belts independent of the motor can sometimes be found as well, like the Pfaff 130s famous cleated nylon drive belt.
Domestic motors are typically rated somewhere between .4 amps (Featherweight) all the way up to 1.5 amps (some Class 15 clones, Adlers etc). While one would think that beefier motors would yield higher top speeds, this isn't always the case. Take the gear driven Singer 301a for instance, it has a .6 amp motor and is nearly 50% faster than my Kenmore 1803 which has a motor rated at 1.2 amps. The Kenmore, however, has a much higher torque due to it's dual pulley system. Performance, ultimately comes down to a complex combination of motor efficiency, amperage, gearing system and even resistance in you machine. The moral of the story? Test the machine out by making a sample using fabrics you intend to work with!
I often hear people saying that they prefer gear driven machines over belt driven machines because they are more durable. While this may be true on a well cared for precision machine, lots of gear driven machines have a certain degree of slop in them due to years of abuse and if you have a later Kenmore, you'll just have slop, regardless of it's condition! Just be aware of this when you come across a barnyard find.
In my experience a properly adjusted belted motor will perform just as well as a gear driven motor--there's a reason why industrial machines use V-belts! On the subject of belts, a common pitfall is to assume that a taut belt tension is better, but in practice the reverse is true. While you don't want your belt so loose it will fall off, having a bit of slack will actually yield smoother acceleration control and even a higher top speed!
I personally prefer external motors for their versatility: belts can be easily replaced, and external motors can be upgraded with minimal effort. It is difficult if not impossible to upgrade an internal motor, as they have a very specific shape designed to fit with the chassis of the machine. If you feel your domestic external motor isn't powerful enough, you can even use a low RPM industrial motor on your rotary hook domestic! In fact, it isn't uncommon to find domestic Pfaff 130s, Singer 1200s and Bernina x40s using this configuration.
On the other hand, it is hard to argue with the sleekness of having your motor tucked inside your machine!
Which type of motor do you prefer: Internal or external?
Stay tuned, I'll be covering many more topics such as how to differentiate shank types, the merit of plastic vs metal gears, different cam systems and much more in this ongoing series.