Upper Knife for White 504 (Compatible)

Replacement upper knife for White 504. The fitment below is taken from the distributor's own listing for this part. Supplied as a compatible aftermarket part — it is not a manufacturer-original part.

This list comes from the distributor's listing for this part. If your model is not named, do not assume it fits — check the part you are removing against the specification below, or ask us with your model number before ordering.

What this part does

Serger knives are the two blades — upper and lower — that trim the fabric edge just ahead of the needles. The upper knife is usually carbide or hardened steel and moves; the lower knife is fixed. The lower knife wears first because the upper cuts against it.

Specifications

How to tell if this is the right one

Knives are machine-specific. Use the model list on this page; a knife from a different model may be the wrong length, angle or mounting. Order upper and lower as a pair when the machine has been cutting badly for some time. This is the <strong>upper</strong> position; the opposite position is a different part.

Signs you need this part

Fabric edge is chewed or frayed rather than cut cleanly, the knife pushes thick fabric instead of cutting it, or you hear the blades clacking without cutting.

Fitting it

Unplug the machine. Open the front cover, loosen the knife clamp screw, swap the blade and set the new blade so its edge sits level with the needle plate (lower knife) or just below the lower knife edge at the bottom of its stroke (upper knife). Turn the handwheel by hand to check clearance before powering on.

Questions about this part

Does this knife fit the White 504?

Yes. The White 504 is on the distributor's fitment list for this part. If your model is not listed on this page, send us the model number and we will check before you order.

Is this the original White part?

No — it is a compatible aftermarket part made to fit the models listed. It is not a manufacturer-original part.

Upper or lower — which one do I need?

The lower knife is the fixed, flat blade and wears fastest. If the cut is ragged, start with the lower knife. If the machine will not cut heavy fabric at all, replace both.

How long does delivery take?

Orders are dispatched from our distributor's US warehouse. We do not hold stock ourselves and cannot promise same-day dispatch; current delivery estimates are shown at checkout, and we will email you if an item is back-ordered.