Glass cutter

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Commercially available glass cutter with six cutting wheels
Glass cutter for scratching sticks and tubes

A glass cutter is a tool used to cut glass .

The term glass cutter is misleading, because a glass cutter does not actually cut the glass. The fissure created by the incision leads to a stress concentration ( notch effect ) and along this the glass breaks under controlled pressure, tensile or bending loads.

In addition to the hand-held glass cutters described in this article, there are also machine-operated glass cutters for industrial use.

Classification

Glass cutters are available in very different designs and price ranges and for different applications, cuts and for different glass thicknesses;

construction

Hand-held glass cutters are made up of the following parts

Cutting tool

Diamond or steel wheel . The thicker the glass to be cut, the greater the cutting angle must be. The cutting angle is the angle at which the flanks of the cutting wheel converge.

Recommended cutting angles for different glass thicknesses
Glass thickness Cutting angle   Glass thickness Cutting angle
2-3 mm 120 ° 6-12 mm 150 °
2-4 mm 127 ° 6-15 mm 155 °
2-6 mm 135 ° 10-19 mm 158 °
4-8 mm 140 ° 19-25 mm 160 °
6-10 mm 145 ° 19-25 mm 165 °

Cutting head

This holds the cutting tool and is used to transmit power between the handle and the cutting tool. The cutting head is either firmly connected to the handle or rotatably mounted. With oil-guided glass cutters, it guides the cutting oil from the handle via a wick to the wheel.

Handle

Different handle shapes allow different handles when guiding the glass cutter, such as a pencil handle, a grip between the index and middle finger or a fist grip. In the case of oil-guided glass cutters, the handle also serves to hold the cutting oil .

application

Oil-guided glass cutter with rotatable head and special handle, handle about halfway filled with cutting oil
Glass saw to rescue vehicle accidents

The glass cutting itself takes place in several work steps:

  1. Preparations for the workplace
  2. Preparing the glass: The glass is freed from dirt and ideally has ambient temperature.
  3. Scoring the glass (cutting): Before cutting, the glass cutting head is immersed in cutting oil or the glass itself is coated with the cutting fluid. Most of the available glass cutters are designed to be pushed or pulled over the glass in a vertical position with constant pressure and constant speed.
    1. Pulling glass cutter: This is the most common technique. Suitable for ruler cuts , where the head of the tailor is dragged along a ruler or square to get a straight cut, or for freehand cuts to make auxiliary cuts and to cut along recorded lines or templates.
    2. Slide glass cutter: with special glass cutters / handles this technique is possible for free-hand cutting. It allows a view of the cutting head and the line in front of it.
  4. If the cut is interrupted and the tool is passed through the existing fissure again, the new fissure acts like a relief notch and reduces the effect of the first cut.
  5. Opening the fissure, breaking: the fissure is opened by applying pressure to the glass. With straight cuts, the pressure is applied from the bottom to the top at one of the two cut ends. Usually by placing a small piece of wood under it or the handle of the glass cutter. In the case of freehand cuts , appropriate aids such as three-point pliers , running pliers , crimping pliers , glass breakers etc.
    1. Alternatively, the cut can also be opened by tapping. Light hits with the glass cutter against the glass pane below the notch widen the fissures created by the cut and ultimately lead to the glass breaking at the cut edge. The expansion of the crack with each stroke can be followed with the eye. The result can be a break that better follows the cut. Another opinion is that this process leads to stronger chipping, unclean edges and felling .
  6. Finishing the edges: With special sanding belts and machines, the edges can be finely sanded or polished. For the hobby area or for art glazing, it is also sufficient to hone the edges with a whetstone .

To physics

The physico-chemical processes that occur when cutting glass are not yet fully understood, and various theories can be found about them.

The notch effect caused by guiding the cutting tool along is decisive for glass breakage . The influence of the stress curve in the glass can be made visible by methods of stress optics. The weakening of the glass by the fissure created by the cutter is not essential for the breaking process. If a similar deep crack is created by grinding into the glass, the glass will not break along the crack as desired.

Over time, the tension is reduced and the cut becomes "cold". It breaks with increasing difficulty and after days or weeks no longer at all.

The cutting fluid molecules attach to the tip of the crack and lower the energy required to break the glass molecules. To do this, a cutting fluid must meet several requirements

  • it should be thin
  • their molecules should have the highest possible binding energy
  • their molecules should be as small as possible

In terms of its physicochemical properties, water would be a good cutting fluid. However, since it can promote the corrosion of metal parts of a glass cutter, synthetic cutting oils are found in practical use.

Web links

Commons : Glass cutter  - collection of images, videos and audio files
Wiktionary: Glass cutter  - explanations of meanings, word origins, synonyms, translations