Glass Basics: Scoring and Separating Recommendations Technical Information Paper TIP 305 Issued: November 2004 Supercedes: xxxxx Scoring is performed to separate a sheet of glass into smaller pieces with good quality edges. A score wheel, and typically a scoring machine, is used to create a small “flaw” or shallow crack by drawing the score wheel across the glass under load. This crack is called a median crack. The glass is then bent to extend the median crack through the thickness of the sheet, creating two pieces. The quality of the median crack controls the ease of separation and the quality of the edges. The crack should be continuous throughout the length of the score and have a consistent depth. This provides ease of separation and minimizes unwanted chips and cracks. Scribe load Radius Tip angle Surface Median crack Figure 1. Downward pressure on the scoring wheel should be applied in a manner that creates a median crack of a consistent depth throughout the length of the score. Figure 2. A photo of a score wheel in the process of creating a median crack Figure 3. After creating the median crack , applying downward pressure on both sides of the scoreline will enable glass separation.

Key Variables Key variables affecting the quality of the score are: score wheel geometry, wheel tip finish, and scoring machine settings such as scoring load and speed. Some general guidelines for the effects of score wheel geometry and finish on score quality are as follows: • For a deeper median crack scored at the same load, use a narrower wheel tip angle or smaller diameter wheel. (Tip angle has a stronger influence than wheel diameter.) If a median crack is not deep enough more bending force will be necessary to separate the glass. If too high a force is needed to separate the glass, the...

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