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6.1. Prescraping
By prescraping, the working traces on the rough-finished work-piece surface are eliminated and the surface is smoothed. The surface is scraped by long, strong strokes, the flat scraper has to be applied in an inclined position to the existing working traces using the sides alternately.
Figure 15 - Prescraping
Each scraping stroke must be carried out by increasing and decreasing manual pressure, so that no ledges occur on the surface. The scraper is drawn back without pressure in order to save the cutting edge.
6.2. Inking
By the inking block, the inking paste is spread on the inking device extremely thin and rubbed.
Figure 16 - Spreading of inking paste
Small workplaces are moved slowly and in circles on the inked surface plate; on large workpiece surfaces, the straight edge is drawn over the surface.
At places where surfaces get in touch with one another, ink is rubbed down, whereas in deeper places, ink is accumulated. Extremely deep spots are not touched by the ink.
Figure 17 - Surface appearance
A surface appearance is created this way:
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Slightly coloured spots: |
highest points |
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Strongly coloured spots: |
medium position |
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Noncoloured spots: |
deepest points |
6.3. Spot scraping
In order to achieve closely adjacent surfaces, the highest points (slightly coloured) are scraped with frequent change of direction and checked against a master plate until there are three times as many highest points in comparison with deepest points.
In this process, the flat scraper is pushed over the highest points in short curves.
Figure 18 - Prescraping
6.4. Finishing and pattern scraping
If the quality of spot scraping does not lead to a satisfactory result, the surface is reworked with the help of the pulling scraper which is drawn over the highest point with slight pressure by the hand.
Figure 19 - Finishing
The pulling scraper may be used for making a pattern if it is drawn over the workpiece in regular movements. Common patterns are stripes and plaited patterns.
Figure 20 - Striped pattern
Figure 21 - Plaited pattern
Patterns are scraped if:
- workpieces shall look better;
- the adherence of the greasing film shall be guaranteed with sliding surfaces;
- the abrasion of guiding surfaces shall be controlled (in case of wear the pattern disappears).
What sequence of operations characterizes the planing of a plane
surface?
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What characterizes the
prescraping?
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What characterizes the spot
scraping?
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What characterizes the finishing
operation?
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