Rewinder Bottom Slitter Knives

Rewinder Bottom Slitter Knives

Persistools rewinder bottom slitter knives are precision rotary cutting components used together with upper slitter knives in rewinding, slitting, and web converting systems.

During operation, the upper knife overlaps and contacts the cutting edge of the bottom knife. As the material passes through the cutting zone, the two edges work together to create a continuous shear cut.

Stable cutting performance depends on the relationship between:

• Upper knife position
• Bottom knife edge geometry
• Overlap depth
• Side contact
• Rotational accuracy
• Surface finish

For this reason, bottom slitter knives require high dimensional accuracy and carefully ground cutting surfaces.

TCT-Tipped Construction

Most rewinder bottom knives use a steel or HSS body with brazed tungsten carbide cutting rings.

This construction provides a practical balance between:

• High wear resistance
• Stable rotation
• Lower manufacturing cost
• Good mechanical toughness
• Long cutting life

Instead of manufacturing the entire knife from carbide, tungsten carbide is concentrated in the working edge area where wear resistance is most important.

Single-Edge and Double-Edge Designs

Bottom slitter knives can be manufactured with one or two carbide cutting edges.

Single-Edge Bottom Knives

A single carbide ring provides one working cutting edge and is suitable for standard slitting applications.

Double-Edge Bottom Knives

Double-edge designs provide a cutting edge on both sides of the working ring.

After one edge becomes worn, the knife can be reversed or repositioned to use the second edge, effectively extending usable service life before replacement or regrinding.

For this reason, double-edge constructions are widely used in continuous production.

Solid Carbide Bottom Knives

For selected high-precision machines, bottom slitter knives can also be manufactured from solid tungsten carbide.

Solid carbide construction provides:

• High dimensional stability
• Excellent wear resistance
• Stable cutting geometry
• Consistent concentricity
• Long edge retention

However, the manufacturing cost is significantly higher, so solid carbide bottom knives are generally used only where machine accuracy and production requirements justify the additional cost.

Mirror-Ground Cutting Surfaces

Bottom slitter knives commonly require very fine grinding on the working surface.

A mirror-ground or highly polished finish helps maintain:

• Stable contact with the upper knife
• Low friction
• Reduced material marking
• Consistent overlap
• Smooth rotational cutting
• Controlled wear

This is particularly important in high-speed slitting systems where even small surface irregularities can affect cutting quality.

Controlled Cutting Edge Depth

The cutting edge of a bottom knife is generally relatively shallow.

The bottom knife must provide enough working edge for the upper knife to overlap and shear against, while preventing excessive penetration depth.

A controlled edge height helps:

• Maintain stable upper/lower knife contact
• Limit cutting depth
• Reduce unnecessary blade interference
• Protect the knife body
• Improve repeatability during setup

The final edge depth and geometry depend on the machine design, processed material, and top-knife configuration.