Mandrel holder

For the manufacture of colophony core wire, the colophony feed pipe is inserted in bore d and a mandrel with mandrel-holder, similar to that shown in Fig. 12, is employed. With the arrangement being as shown in Fig. 12, the mandrel-holder a is inserted in the container bore from the rear it is provided with channels h to allow for the passage of the tin,... 

Having established the correct flow of lead, a pipe is first extruded and its wall thickness gauged. Any undue variations may be obviated by radially adjusting the die with the help of the centering screws. The wall thickness of the sheathing is obtained by axially adjusting the mandrel-point and the mandrel-holder respectively, with the help of the rear screwed joint. 

The concentricity of the wall thickness over the full length of the cable is largely affected by the correct seating of the mandrel-holder care must be taken that the point cannot alter its position, i. e. deflect elastically, and for this reason it must be supported as close to the die as possible. 

A horizontal press of this type is shown in Fig. 41. The lead is charged in a container disposed concentrically to the mandrel and the mandrel-holder respectively, and after solidification it is forced through the die in a manner similar to that used in a lead pipe press, see p. 4. 

The tip of mandrel I is seated in a mandrel-holder m of which one end is provided with a threaded flange n and screwed into the container... 

The press capacity is 2,650 tons. It takes a lead charge of 450 kg at a container diameter of 400 mm its mandrel-holder diameter is 240 mm and its effective stroke 485 mm. The extrusion ram pressure is approx. 3,250 kg/cm. ... 

For this purpose mandrel a and mandrel-holder h are provided with a central bore which accomodates feed pipes c and d. The cooling water is admitted to the hollow space in the mandrel through a number of holes drilled into pipe c and flows back through the mandrel-holder into chamber e of the piercer bar /. The water passage from the ram-holder g to the movable piercer bar / and vice versa takes place through two immersion tubes h arranged side by side, of w hich only one is shown in Fig. 134. 

A straight or tapered fine thread is provided in the mandrel-holder to secure the mandrel. The tapered thread which permits of changing the mandrel rapidly, has not found a wide application as the mandrel tends to loosen easily. 

The cross-section of the core of the thread has to take heavy tensile stresses both during extrusion and when pulling the mandrel out of the extruded tube. That is why bayonet unions between mandrel and holder are not used, because in such case the diameter of the head of the mandrel-holder would be too wide and the extrusion ram would be weakened too much. 

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