Upper and Lower Serger Knife Maintenance

Upper and Lower Serger Knife Maintenance

These are tips on how to install the upper and lower serger knives. You will also learn how to sharpen the knife and other questions.

Types of overlocker sewing machine knives

Lower Serger Knives

The upper and lower knives of modern models are attached at bottom part of serger, as shown on this photo.

Upper and Lower Serger Knife

The knives 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.

The upper knife can be turned off

Both types of knife designs have 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.
At modern models of overlocker you can turn off the upper knife also. See the instruction of your overlock.

How to remove and replace blades

 How to remove and replace blades

Attachment the 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.
Note: Before the removal blades a serger you need be sure to disconnect a serger from the network.

How to change both serger blades

Lower serger knife is attached with screw having a special washer. Way of attaching the lower serger knife on other old models may have minor differences but the principle of fastening will be similar.
In any case to remove this knife you will need to loosen the screw using big flat screwdriver.

How to change both serger blades

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 surface. In addition to it the blades must be correctly positioned relative to the surface of the needle plate and should be properly positioned relative to each other.
When you will be 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 - not more than 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.

How to change both serger blades

In this photo you can see the blades of modern serger. These knives can 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

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 special tools. Self-sharpening serger blades will be bad to cut fabric.
Note: The knives of different manufacturers the overlock sewing machines have own differences and features. Keep this in mind when buying new blades.

English isn't my first language, so please excuse any mistakes and help correct them.
E-mail for sending is on the contact page.

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