Hook maintenance
The rotary hook is an extremely complex kinematic device. It requires great accuracy in every stage of its
manufacture and by bestowing care and attention on it during its use you will ensure its best performance, full
efficiency and a greatly prolonged life.
The rotary hook is the most important component in lockstitch sewing machines. The person responsible for its
purchase should always demand a product of the highest quality, as the use of hook that is not of first quality, will
substantially reduce the efficiency of the whole machine. Consideration should also be given to the fact that the
increased productivity and superior stitching quality of a high quality product, long term, will more than offset the
savings realized by buying cheaper hooks tools.
Cerliani’s hooks are manufactured to the highest quality, using the finest materials, and by production techniques,
that are state of the art, each one, guaranteed by over sixty years of experience.
The new hooks are normally coated by rust-fighting oil which dries with time. Therefore, prior to their use, it is
necessary to wash them thoroughly with petrol/gasoline or mineral oil and then provide an abundant lubrication.
The same procedure has to be followed every time one plans to reuse a hook that has not been used for some time.
In order to maintain the rotary hook in good working order it is advisable to check and service the hook at regular
intervals. This will also help to avoid possible irreparable damage caused by deficiciencies of the lubrication system
or incorrect regulation of the oil flow. Preventive maintenance has to be executed scrupulously and systematically
and it would be considered good practice to follo w the time table as shown below. Obviously, each company can
adapt these guidelines to the needs of their own machinery.
Standard time-table for the preventive hook maintenance
Description of operation Frequency Remarks
Remove sewing debris to avoid them becoming abrasive. Check oil
level.
Check the oil feed to the hook and adjust if necessary.
Wash the hook, without dismantling it, with naphta or mineral oil,
while turning the machine by hand to avoid seizing; afterwards
lubricate while continuing to turn the machine.
Remove the hook from the machine. Take out the base.
Carefully clean and wash all the components, making sure that the
lubrication channels are not clogged.
Check that there are no signs of needle stabs, scrapes or burrs on
the hook point and all areas over which the thread passes. Light
damage can be removed by using fine grain sanding paper or
emery cloth. Polish the area, using a soft cotton polishing wheel in
conjunction with a fine grain polishing compound.
Carefully reassemble the hook, lubricate it liberaly and re-install it
in the machine.
Retime the hook and check that the lubrication system is correctly
adjusted. Perform a stitching test on suitable materials.
Daily
Weekly
Every two
weeks
Monthly
Use a brush or compressed
air.
For adjustments always
follow manufacturers
instructions.
For this operation only use a
brush, never an air gun, as
this may cause solvents to
be blown into neraby
bearings, degreasing them
and causing seizure.
For correct regulation of the
hook lubrication system, see
note at the bottom table.
Lubrication flow test (with horizontal axis hooks); remove the needle plate and the feed dog. Fix a sheet of paper to
the bed of the machine, over the exposed hook. Run the machine at maximum speed for approximately 10 seconds.
Lubrication is considered correct when 2 parallel rows of oil dots show on the paper after this period. To increase or
decrease the amount of oil flowing to the hook, adjust the flow regulator, that should be incorporated into the
machine. It should also be noted that if too much oil flows to the hook, the excess will be thrown by centrifugal
force against the needle plate with the risk of it staining the material. If on the other hand, too little oil reaches the
hook, this will cause undue wear, thus shortening the life of the hook.
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