In the first post of this series, Proper Bernina 1000-Series Maintenance: Part 1, I breifly described servicing the head frame of a Bernina 1000-Series sewing machine, and a couple of the common problems I see while servicing that group of parts. In this post, I’m going to give you a little information about what is one of the dirtiest parts in any sewing machine, the hook.
There are 2 main classifications of hooks. The first is a rotary hook, and the other an oscillating hook. A rotary hook spins in one direction, while a oscillating hook moves back and forth. A hook, regardless of type, is what is responsible for picking up or catching the upper thread, forming a stitch. When the needle has fully penetrated the fabric during sewing, and the needle is on its way back up, a loop is formed on the back of the needle, and this loop is what the tip of the hook must catch, or the stitch will be skipped.
Hooks can have various types of damage, and a broken hook tip or any burrs made by needles striking it can render a sewing machine completely useless. However, damage is not usually the problem. Most often, if there is a problem related to the hook, it’s that it is dirty, dry, or both.
Hooks need constant lubrication. In almost any sewing machine, even brands that are not Bernina, if the hook lacks sufficient lubrication, it can sound very loud when it runs. Sewing machines have very precise adjustments and settings, and a hook that is not lubricated may cause stitches to look funny. The machine will usually sew, but it just won’t form a perfect stitch.
Hooks need to stay clean. Even between annual services, your sewing machine needs to have the lint removed from the hook area on a regular basis. When lint is allowed to accumulate, the lint can get packed into dense “lint nuggets”, and obstruct the free movement of the hook, again effecting the quality of the stitch. If the lint accumulation gets really bad, the machine may not sew at all. Bernina rotary hook machines seem especially prone to poor stitch quality when the hook area gets dirty, so owners of these machines should pay close attention to lint build up.
An oscillating hook type machine has a major benefit over a rotary hook machine, in that it is possible for the owner to remove the hook and clean the place where it came out of, the hook race. Since removal of a rotary hook involves throwing off the timing of the machine, it’s not recommended that owners of these machines try to remove them for cleaning. So then why have a rotary hook at all? I believe Bernina says their 9 millimeter stitch width is only possible because of the rotary hook.
Bernina had a series of machines that came out with half plastic / half metal hooks. I’ve seen a few model 1008 machines with this hook type, and if your 1008 has one of these hooks, be advised against using mono-filament thread in the machine. This type of thread can cut grooves into the plastic part of the hook, and the hook may be damaged beyond repair. The good news is that the replacement hook has an all metal body.
I hope you learned something about hooks and cleaning your sewing machine. Come back soon for part 3 of this series.
Posted in Bernina