Knurled surface

Cox et al. [101] used several kinds of enhanced tubes to improve the performance of horizontal-tube multiple-effect plants for saline water conversion. Overall heat transfer coefficients (forced convection condensation inside and spray-film evaporation outside) were reported for tubes internally enhanced with circumferential V grooves (35 percent maximum increase in U) and protuberances produced by spiral indenting from the outside (4 percent increase). No increases were obtained with a knurled surface. Prince [102] obtained a 200 percent increase in U with internal circumferential ribs however, the outside (spray-film evaporation) was also enhanced. Luu and Bergles [15] reported data for enhanced condensation of R-113 in tubes with helical repeated-rib internal roughness. Average coefficients were increased 80 percent above smooth-tube values. Coefficients with deep spirally fluted tubes (envelope diameter basis) were increased by 50 percent. 

Anchorage ag-k(o-)rij (15c) n. Part of an insert that is molded inside of a plastic part and held fast by shrinkage of the plastic onto the insert s knurled surfaces. (1) Property or profile of metal or wood substrate to enhance the adhesion of a coating. (2) Adhesion of rubber to fiber, fabric, metal or other material to which the rubber compound is applied by calendering, welding, cement spreading, or other means. 

Stripping torque n. (1) Of a self-tapping screw, the twisting moment in Nm required to strip the threads formed by the screw in a softer material. (2) Of a molded-in insert, the torque required to break the mechanical bond between the plastic and the insert s knurled surface. 

The operative word is "simple." Surfaces which are flab and don t have crevices, pockets, cracks, blind or tapped holes, cupped stmctures, or knurled surfaces are those identified as "simple." Simple surfaces don t trap droplets of liquid. Simple surfaces are wet with films which evaporate rapidly. 

Clean the surface with a wire brush to loosen the oxide film and then wipe it off with a soft cloth. The use of a wire brush serves a dual purpose first, scraping and removing the oxide film, and secondly, providing the surface with a moderate knurling (roughness), which helps to make a better surface-to-surface contact and, in turn, a better joint. 

The results are shown in Figure 26.58 for two blunt surfaces Knurled aluminum and knurled steel. Aluminum produces a lower abrasion loss than steel. On both surfaces, however, the abrasion was much higher when MgO was used as an absorbing powder than with the mixture of Fuller s earth and alumina. The two compounds examined were an NR compound without antioxidant and one with two parts of Nonox ZA. There is a very clear difference between the two compounds indicating that oxygen plays an important role. 

FIGURE 26.58 Abrasion of two natural rubber (NR) tread compounds, one unprotected, the other with two parts Nonox ZA on a knurled Aluminum and a knurled steel surface, respectively, in the presence of (a) magnesium oxide (MgO) powder and (b) a dust mix of Fuller s earth and alumina powder. (Deduced from Schallamach, A.,Appl. Pol. Sci., 12, 281, 1968.)... 

Instant tack labels find special usage on seals, pleated overwraps, and various header labels. They are not used for bottle or can labeling. Blister and strip packs are classified as part of this category, as we require the temperature of the lacquer to be raised high enough to obtain a permanent bond with the inner surface of the base material. Pressure needs to be applied as well, and usually there will be a knurling implanted onto the mating surfaces. 

When a condenser with a cooled distillate tube is used as dephlegmator the problem is to exactly set the desired reflux ratio. The cooling surface of the dephlegmator shown in Fig. 296 can be adjusted as desired by operating the knurled nut, thus varying the position of the stiU pot [80]. 

E is Young s modulus. An incorrect interference can result on the one hand in cracking of the part, and on the other in loosening of the joint. Stress relaxation in the polymer and differences in thermal expansion coefficient must both be taken into account. Knurled metal surfaces enable the polymer to creep into depressions and increase joint strength. 

PS can be readily molded with metallic inserts, however the inserts should be pre-heated to 80 to 120° C (176 to 248° F) prior to being placed into the mold in order to avoid molded-in stresses occurring. All metallic inserts should be thoroughly degreased and have some form of undercut feature on their external surface (i.e. in the form of a knurl or groove). 

Knurling is a process whereby indentations are formed on a smooth, usually round, surface to allow hands or fingers to get a better grip. 

The cross-slide is positioned so that the knurls are above the centre of the workpiece where they are adjusted to contact the workpiece surface using the adjusting screw. Slender work may have to be supported using a centre in the tailstock. 

With the lathe running at a low speed and cutting fluid applied, the knurls are tightened until the required form appears on the workpiece surface. 

Figure 11-72. Knurls and grooves can serve to anchor inserts in molded products. They should be flush with the top surface or in contact with an assembling member to prevent their jacking out.

Use an insert with a coarse knurl for maximum holding power. The knurl should end below the surface of the plastic. 

The inside surface of the bowl can be plain machined. However, some effort is often made to encourage cake to stick to the bowl, to aid scrolling instead of slipping round with the conveyor. The means of doing this could be by knurling the inside of the bowl for instance. This can wear smooth relatively quickly. More often longitudinal ribs are welded, or a liner with similar ribs is fitted (see Section 2.2.4.3). 

Instead of a liner, many bowls have longitudinal ribs spot welded to the inside of the bowl. Another alternative to a liner is knurling or roughening of the bowl, which is a simple procedure, but would normally be done only as a temporary measure as such surfaces will be quickly worn smooth. 

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