Upper and Lower Serger Knife Maintenance
Tips on how to install your upper and lower serger knife replacement. You will also learn how to sharpen the knives and other questions.
Two types of overlocker sewing machine knives
The upper and lower knives of modern models are attached at bottom part of serger, as shown on this photo.
Older models of overlock sewing machines have another design. One knife blade is mounted on top, second blade is attached on bottom part of serger.
But such an old knife design is one useful feature - upper blade can be turned off; you need pull it to the right and lift upwards. This feature of the upper blade unit can be useful for making some special overlock lines.
Note: Before lifting the upper knife, make sure that it will not touch the loopers and other moving parts of serger.
How to remove and change both serger blades
Attachment of top blade can be having different design; it is depend on the model of overlocker. But often of all, you need just to loosen the screws and pull out the upper blade.
Note: Do not forget that the upper knife can be moved to the right also.
Before the removal of the serger blades you need be sure to disconnect a serger from the network.
Lower serger knife is attached with screw having a washer or otherwise in a similar way. But in any case to remove this knife you will need to loosen the screw with a screwdriver.
Now let's see which should be the parameters of the knives adjustment. Look on the cutting plane of the blades. Both serger knives have certain angle of the cutting surfaces. And the blades must be correctly positioned relative to the surface of the needle plate and each other.
When you will install new knives on your serger you need to use simple rule. Lower serger knife must be mounted flush to needle plate (or just below - 1 mm).
The upper knife must be mounted so that its cutting edge dropped below the cutting edge of the lower knife, approximately 1.5 mm.
Note that lateral surfaces of the overlock blades must be pressed against each other with a certain force. This force is created by spring compression of upper knife, which you can adjust.
In this photo you can see the blades of modern serger. These knives are easy to remove and change. You need to have only a Phillips screwdriver.
When installing such new knives on the serger you need to use the same rules. Lower serger knife must be mounted flush to needle plate (or just below - 1 mm). And the upper knife (in the lowermost position) must be below the lower knife, approximately 1.5 mm.
How to sharpen the knives
Can you sharpen the knives with their hands at home? No!
Look at this photo. Cutting surface of an upper knife has very complex shape. Besides, the cutting knives plane has a certain angle. This can be done only using a special tools.
Note: Each manufacturer of overlock sewing machines has own differences and features of serger knives. Self-sharpening serger blades will cut the fabric very bad.
English isn't my first language, so please excuse any mistakes and help correct them.
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