The upper knife is the main component and is what makes the sewing machine an overlock in the first place, because in combination with the lower knife it enables the precise cutting of the fabric and is jointly responsible for the fast and precise operation of the machine. On many overlock machines the upper knife can be deactivated by folding or turning it to allow processing or sewing together without cutting.
The knife is suitable for the SL3335 and SL3487 overlock machines. Always make sure that the blade is sharp!
