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13. Forging top and bottom swages

Agricultural engineering in development


Agricultural engineering in development


Agricultural engineering in development


Agricultural engineering in development


Agricultural engineering in development


Material. Flat vehicle-spring steel as thick as possible; short length of railway-line steel; mild-steel rod 8 to 10 mm for handles.

Additional tools. Hot set; fullers; flatter; hacksaw; short, triangular former (either a softened piece of a three-sided file or a piece of 12-mm square-section steel sawn diagonally).


Small top swages can be made in much the same way as top fullers. First form a head as for fullers in Job 12. Upset the opposite end to give enough material for the working end. Mark out the centre line of the upset end and cut a shallow groove with a hacksaw (Figs 132A and 133). Place the short, triangular former on the face of the anvil (Fig. 134) and hammer the heated job squarely on to it in order to begin spreading the metal. As mentioned above, a short length cut from a worn three-sided file in the softened state is ideal here. If this is not available, a short length (60 mm or so) of square-section steel can be sawn lengthwise across its diagonal to serve the same purpose. The topmost angle of this helping piece should be slightly rounded to reduce the possibility of cracking the workpiece when the groove is widened.

After grooving the metal over the former, the job is reheated and worked over a piece of round-section rod (Fig. 135). Start with a rod of lesser diameter than wanted in the finished job. For example, for a swage 10 mm in diameter, the rod would be worked over 8-mm rod followed by rod 10 mm in diameter, which would be worked into the job to half its diameter. For a 12-mm swage, use rods 8, 10 and 12 mm in diameter, gradually working up to the finished size.

The larger the swage, the greater will be the number of different-sized rods used in working up to the finished size.

If you try a short cut and work the job over only the finished size of the rod, excessive upsetting of the work will occur and the resulting groove will always be oversize.

On completion of the forging, the job is again heated and normalized. Any finishing touches can now be carried out by grinding or filing or both. The groove can be cleaned out with a round-section file. All sharp edges should be rounded, particularly at the ends of the grooves. Sharp edges cause indents in workpieces and these may lead to cracks. Again, a rod handle is fitted as before but the handle must be at right angles to the swage groove (Fig. 136).

Larger swages are made in a similar manner but more robust sections of material must be used. Here again, railway-line metal is useful. You can also use large square-section spring tines from cultivators or heavy-section drive shafts from lorries or tractors; die latter are of nickel steels that are very tough although they contain insufficient carbon for hardening and tempering. They will normally stand up to fairly hard work on hot metal.

Whichever is used, a blank similar to that shown in Fig. 137A is required. Sizes are a matter of choice, but enough metal should be available to make a groove 40 or 50 mm long. The shank of the tool should be not less than 25 mm square in section (Fig. 137A) and preferably more than this, perhaps 40 mm for large swages. If railway metal is used, the top section of rail is cut off and a length of 80 to 90 mm is flattened to give a rectangular section as big as can be readily worked from the blank. After flattening, the ends should be neatly squared up on the face of the anvil. Shoulder with fullers and draw-down the shank to a square section. The head of the tool is next tapered and fullered recesses are made to accommodate the handle. Note that when using square sections the corners only are fullered fairly deeply. The centre of the face can be then marked and a shallow hacksaw cut made (Fig. 133). The swage groove is again worked as described earlier (Figs 137B and C).

Agricultural engineering in development


Agricultural engineering in development


If electric-arc welding is available, some swages can be made in pairs by tacking the pieces together (Fig. 138). A pilot hole is then drilled (Fig. 38), and this is followed by the finished-size drill. The job is then broken apart and the weld spots (W in Fig. 138) are filed or ground off.

Bottom swages are required to match the top tools. Material requirements are similar. A useful swageing tool is illustrated in Fig. 139, showing a number of swageing grooves contained in one tool. The tool is a flattened piece of steel such as railway metal, with one end drawn-down to fit the tool hole of the anvil (A in Fig. 139). Aright-angle bend has been made, leaving 25 to 30 mm to fit the tool hole. The remainder, about 80 mm, is carefully flattened while hot to lie closely on the anvil face when the shank is in place in the tool hole. Grooves can now be fullered into the tool up to about 10 mm in size. Start with a smaller fuller than the required finished size and complete the grooves with rods of the correct diameter driven in to half their diameter. Finally, true up the work and clean up by grinding, filing or both.

Suitable blanks for larger bottom fullers can be made as for the bottom fullers shown in Figs 127 and 128. At a good yellow heat, the block is forged flat while in place in the tool hole. Next, square up and flatten the sides. Grooves can again be fullered in (Fig. 140). Again, start with a small fuller and gradually work up to the required size. The depth of grooves can be checked with a straight-edge and rule (Fig. 140).

Agricultural engineering in development


Agricultural engineering in development


Agricultural engineering in development


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