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Knife Sharpening Instructions

A whole range of cutting problems is caused by improperly maintained blades. Some of these problems are caused by the customer, for example, by replacing the blade too late. This can lead to blade damage as well as machine breakdown. Another source of errors lies in the sharpening and preparation of the blades. This includes proper sharpening, manually honing the blade with a whetstone, straightening bent blades if necessary, and applying a final protective coating to the blades during installation. For this reason, we provide sharpening instructions for our two main blade types.

Grinding Instructions for PERFECTA Paper Cutting Blades, High-Performance High-Speed Steel (HSS) Type F 3000

PERFECTA paper cutting blades are high-quality tools and therefore require careful handling during regrinding. This is the only way to ensure maximum cutting performance.

This work should therefore only be performed by a specialist who has access to properly functioning grinding machines and the correct abrasives.

CAUTION! Never grind dry!

Grinding errors can be avoided by:

Using the correct abrasive
Providing sufficient water cooling
Carefully adjusting the grinding wheel’s pressure
Dressing the grinding wheel in a timely manner

The Right Conditions

It is important to use the correct abrasive, such as segments, grinding cylinders, or grinding cups (see recommendations and technical data). The coolant flow (water with rust inhibitor and coolant additive) should be set to the maximum (150–200 l/min) and directed directly at the grinding area. This ensures adequate cooling and flushes out the abrasive particles that settle in the pores.

Defective grinding machines, excessive grinding pressure, insufficient water cooling, and unsuitable grinding wheels lead to grinding defects. The consequences are: The knife edge exhibits burn marks (yellow-blue discoloration / decarburization), which lead to reduced performance, cracks, and chipping. No replacement will be provided for knives with grinding defects.

The technical procedure for regrinding hardened paper-cutting knives described below applies to all steel grades.

INSERT IMAGE

It is absolutely essential that the steel insert (1) and the unalloyed blade carrier (2) be ground together; that is, the grinding wheel must engage the entire bevel surface (3) at the same time.

This ensures that the grinding wheel is constantly roughened against the unalloyed blade carrier, thereby guaranteeing a good cut on the steel insert. This reduces the risk of burning (decarburization) of the cutting tip. Of course, the coolant flow must be set to the maximum (150 to 200 l/min) and directed directly at the grinding area.

Be sure to select the correct grinding wheels (see recommendations and technical data).

In exceptional cases where only the steel insert (1) needs to be ground (e.g., grinding a preliminary bevel), an extremely soft grinding wheel must be selected. Extreme care is required. The feed per stroke should not exceed 0.010–0.015 mm.

Grinding elements: Segments
Blade grade: F-3000
Abrasive: Grit 46–60 | Hardness H | Bakelite bond
Peripheral speed of grinding head V (m/sec): 20–25
Table speed V (m/min): 20–25
Feed per stroke (mm): 0.01–0.02

Sharpening Instructions for Perfecta Paper Cutting Blades: Fine-Grain Carbide Blades (WIDIA) – Standard, Longlife, and Megalife Types

When resharpening carbide paper cutting blades, follow the instructions below. Perform the steps in the order described.

Cooling Water

It is absolutely essential to prevent the grinding wheel from “burning”!

Therefore, special care must be taken to ensure that a sufficient quantity of clean, filtered cooling water with a coolant additive—which also guarantees the binding of cobalt (clear or emulsion)—is directed precisely onto the grinding point.

Grinding the Base Material (Steel)

Same conditions as for standard carbide.

Peripheral speed: 20–30 m/sec; corundum grinding wheel with Bakelite bond. Feed rate: approx. 25 m/min. Pulse feed = 0.03 to 0.05 mm per 2-meter magnet length.

Pre-grinding of carbide using only the deep-cut grinding method

Same conditions as for standard carbide. Motor speed: 1,450 rpm.

Grinding wheel diameter 250 mm B, D126 - C75 (e.g., Tesch)

Feed rate = 200–300 mm/min, depth of cut 0.01 mm per pass; grinding wheel rotation direction opposite to the blade edge

Pre-grinding only using the deep-grinding method

Motor speed: 1,450 rpm. Grinding wheel diameter: 250 mm, B D20 - C75 (Tesch)

Use the lowest possible hardness. Feed rate: 100–120 mm/min.

A maximum feed rate of 0.04 mm results in a bevel width of approx. 0.7–1 mm. This is performed in a single pass. Grinding wheel rotation direction: against the blade edge

General Information

The grinding machine must be in perfect working order. Above all, the quick-change flange to which the grinding wheel is mounted must rotate without vibration. Tilt the cup wheel slightly until cross-grinding no longer occurs. It is absolutely essential to avoid grinding steel and carbide together. The cutting edge is sharp when it no longer has any nicks. Dressing the ground carbide cutting edge is only possible with the finest diamond lapping stone (e.g., D7).

Straightening

After each regrinding (and possibly even before regrinding), the straightness of the carbide blades must be checked. Even the slightest irregularities (bending of the cutting edges and the back) require professional realignment. This step is an essential part of the complete regrinding process and has a significant impact on the cutting performance and service life of the blades. Take care to ensure that the carbide blade is not damaged under any circumstances.

Recommended procedure: Continuous three-point straightening.

The grinding angles listed below are standard values and can be adjusted depending on the material being cut.