The dividing head

The head consists of a spindle which has a 40-tooth worm wheel attached to it. Meshing with this is a single start worm on a spindle which has a crank and handle attached and which projects from the front of the head (Fig. 11.15). 

An index plate containing a number of circles of different-spaced holes is attached to the front of the head. The spring-loaded pin attached to the crank locates in the required hole circle. The head spindle has a central hole to accept a morse taper centre while the outside is threaded to take a three- or four-jaw chuck (Fig. 11.16). 

Since the gear ratio is 40 1, 40 turns of the crank will turn the spindle (and the workpiece attached to it) through one complete revolution. Alternatively, one turn of the crank will cause the spindle to rotate 1/40 of a revolution or 9°. 

The purpose of the index plate is to further subdivide one revolution of the crank. The index plate contains a number of circles of holes, each containing a different number. The crank can be adjusted for radius so that the spring-loaded pin will fit in any circle of holes. Two sector arms on the index plate can be adjusted to reveal the number of holes required (Fig. 11.16). The number of subdivisions which can be achieved depends on the number of holes in each index plate supplied by the manufacturer. 

For example, a manufacturer may supply three index plates containing circles with the following number of holes  

The dividing head, which is used to hold the workpiece, is clamped to the table of a milling machine using the central tee slot for alignment. If necessary, a tailstock to support the other end of the workpiece, also located in the central tee slot, is clamped at the other end of the machine table. 

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A workpiece is required to have (a) 14 divisions and (b) a n umber of slots 23° apart. Calculate the dividing head settings if the supplied index plate has 21.23.27.29.31 and 33 holes. Answer, (a) 2 turns and 18 holes in a 21-hole circle and (b) 2 turns and 15 holes in a 27-hole circle.)... 

In this fourth edition I have included, by request, additional material including gas welding and the dividing head. I have updated to the current health and safety legislation in Chapter 1 and in relation to abrasive wheels, power presses and manual handling and pictures of machine guards have been added. The section on adhesives has been... 

Pressure Drop. The pressure drop across a two-phase suspension is composed of various terms, such as static head, acceleration, and friction losses for both gas and soflds. For most dense fluid-bed appHcations, outside of entrance or exit regimes where the acceleration pressure drop is appreciable, the pressure drop simply results from the static head of soflds. Therefore, the weight of soflds ia the bed divided by the height of soflds gives the apparent density of the fluidized bed, ie... 

Perfluorobutyric acid [375-22-4] M 214.0, m -17.5", b 120"/735mm, d 1.651, n 1.295, -0.17. Fractionally distd twice in an Oldershaw column with an automatic vapour-dividing head, the first distn in the presence of cone H2SO4 as a drying agent. 

Figure 14.15 Stmcture of the SI fragment of chicken myosin as a Richardson diagram (a) and a space-filling model (b). The two light chains are shown in magenta and yellow. The heavy chain is colored according to three proteolytic fragments produced by trypsin a 25-kDa N-terminal domain (green) a central 50-kDa fragment (red) divided by a cleft into a 50K upper and a 50K lower domain and a 20-kDa C-terminal domain (blue) that links the myosin head to the coiled-coil tail. The 50-kDa and 20-kDa domains both bind actin, while the 25-kDa domain binds ATP. [(b) Courtesy of 1. Rayment.]...

Divide the total head per section by the allowable head per stage to develop the number of stages required in each section. 

As the potential energy term has an essential meaning in hydromechanics, the static head is selected as a comparison quantity. When the energy equation (4.32) is divided by g and integrated, it gives the Bernoulli flow tube equation... 

Pumps are operated in parallel to divide the load between two (or more) smaller pumps rather than a single large one, or to provide additional capacity in a system on short nodce, or for many other related reasons. Figure 3-35 illustrates the operational curve of two identical pumps in parallel, each pump handling one half the capacity at the system head conditions. In the parallel arrangement of two or more pumps of the same or different characteristic curves, the capacities of each pump are added, at the head of the system, to obtain the delivery flow of the pump system. Each pump does not have to carry the same How but it will operate on its own characteristic curve, and must deliver the required head. At a common tie point on the discharge of all the pumps, the head will be the same for each pump, regardless of its flow. 

Regardless of their density, all liquid particles moving at the same velocity in a pipe have the same velocity head [ 11 ]. The velocity head may vary across a medium to large diameter pipe. However, the average velocity of flow, that is, dividing the total flow as cu ft/sec by the cross-sectional area of the pipe is usually accurate enough for most design purposes. 

The General Specification itself can be divided into the following headings ... 

If equation 2.54 is divided throughout by g, each term has the dimensions of length, and, as already noted, may be regarded as a component of the total head of the fluid and... 

From both the time-dependent plot and the time-independent projection, it is clear that the transition path crosses the space-fixed dividing surface qu = 0 several times. These crossings are indicated by thick green dots. As expected, therefore, the fixed surface is not free of recrossings and thus does not satisfy the fundamental requirement for an exact TST dividing surface. The moving surface, by contrast, is crossed only once, at the reaction time head = 8.936 that is marked by the blue cut. The solid blue line in this cut shows the instantaneous position of the dividing surface dotted lines indicate coordinate axes. 

After the hourly heat load is calculated, the capacity of heat source machine would be decided. As total heat produced by heat source machine should be identical to total heat load, the capacity can be calculated dividing head load... 

Bertole et al.u reported experiments on an unsupported Re-promoted cobalt catalyst. The experiments were done in a SSITKA setup, at 210 °C and pressures in the range 3-16.5 bar, using a 4 mm i.d. fixed bed reactor. The partial pressures of H2, CO and H20 in the feed were varied, and the deactivation, effect on activity, selectivity and intrinsic activity (SSITKA) were studied. The direct observation of the kinetic effect of the water on the activity was difficult due to deactivation. However, the authors discuss kinetic effects of water after correcting for deactivation. The results are summarized in Table 1, the table showing the ratio between the results obtained with added water in the feed divided by the same result in a dry experiment. The column headings refer to the actual experiments compared. It is evident that adding water leads to an increase in the overall rate constant kco. The authors also report the intrinsic pseudo first order rate-coefficient kc, where the overall rate of CO conversion rco = kc 6C and 0C is the coverage of active... 

A particle drag coefficient Cd can now be defined as the drag force divided by the product of the dynamic pressure acting on the particle (i.e. the velocity head expressed as an absolute pressure) and the cross-sectional area of the particle. This definition is analogous to that of a friction factor in conventional fluid flow. Hence... 

Compressive strength, or ability of a specimen to resist a crushing force, is measured by crushing a cylindrical specimen (ASTM-D-695) as shown in Figure 14.14. Here a sample of specified dimensions is placed between two heads, one movable and one set. Force is applied to the movable head moving it at a constant rate. The ultimate compression strength is equal to the load that causes failure divided by the minimal cross-sectional area. Since many materials do not fail in compression, strength reflective of specific deformation is often reported. 

Within the cold head, a cylinder is divided into two working spaces and Vj by a displacer. During operation the right space is warm and the left space Vj is cold. At a displacer frequency f the refrigerating power W of the refrigerator is ... 

Fractionally distd twice in an Oldershaw column with an automatic vapour-dividing head, the first distn in the presence of cone H2SO4 as a drying agent. 

Anandamide was isolated from water-insoluble fractions of the porcine brain. It binds to CB1 with rather moderate affinity (Ki 61 nM) and a low affinity for the CB2 receptor (Ki 1930 nM). The name anandamide is based on its chemical nature (an amide) and the Sanskrit word ananda meaning bliss. The chemical structure of anandamide can be divided into two major molecular fragments a polar ethanolamido head group and a hydrophobic arachidonyl chain. The polar head group comprises a secondary amide functionality with an N-hydroxyalkyl substituent while the lipophilic fragment is a non-conjugated c/ s tetraolefinic chain and an n-pentyl chain reminiscent of the lipophilic side chain found in the classical cannabinoids. A number of anandamide analogs have been synthesized and demonstrated to have considerable selectivity for the CB1 receptor in comparison to the CB2 receptor. 

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