Undercut clearance

Figure 14.21 Schematic of a 114.3 mm diameter Fusion screw with a barrier melting section. The lead length of the screw was 131 mm for all sections of the screw except for the barrier melting section. The lead length in the barrier section was 159 mm. The undercut clearance on the barrier flight and the secondary flight in the Fusion sections was 1.3 and 2.5 mm, respectively...

The lead length was 63 mm for the main flight of the screw. The main flight width and clearance were 7 and 0.06 mm, respectively, in all sections of the screw. The undercut of the spiral flight was 0.76 mm. The compression ratio was 2.4 and the compression rate was 0.0029. The ratio of the flight radii in the meter section to the meter depth was about 1.0. The specific rotational flow rate was calculated at 0.94 kg/(h-rpm). ... 

Figure 15.19 Schematic of a four-channel ET cooling screw (courtesy of Jeff A. Myers of Robert Barr, Inc.). The flights that are shaded have a normal clearance with the barrel wall while the flights that are not shaded are undercut...

Mechanical clearance between stem and die bore, sharp edge between tip straight and undercut areas acts to clean die Area of punch opposite head which begins at end of barrel and extends to tip... 

A tool used to part-off or form undercuts requires rake and clearance in the direction of feed but also requires side clearance to prevent rubbing in the groove produced. Fig. 7.9(b). 

Bird applicator n. Device used for the laboratory application of coating of a prescribed thickness to test panels. It is a machined steel bar with a fixed clearance having a beveled undercut to guide the coating material. 

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