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4. Right-angle welded joint, using a cleft preparation; forging a bending dog

Agricultural engineering in development


Agricultural engineering in development


Agricultural engineering in development


Agricultural engineering in development


Agricultural engineering in development


Material. Round section of mild steel 16 to 20 mm in diameter and 700 mm in length.

Additional tools. Bottom swage to suit diameter of metal used; hot set or chisel.


This workpiece shows another use for the cleft preparation and at the same time will produce a tool useful for many bending and adjusting jobs. It is a good idea to have several such tools of different sizes.

Cut off a piece of metal 100 mm long and upset (Fig. 21 A). This is then split with a hot set or hot chisel as in the previous job and formed to shape (Fig. 21B). Make a prominent centre-punch mark 140 mm or so from one end of the other piece. Heat to a near-white heat at this mark, cooling with water to control the length of the heat, which should be only about 40 mm and upset to gain 3 or 4 mm on the diameter at this point (Fig. 21D).

Reheat to a yellow heat and scarf using the ball of the hand hammer while working over the beak (Fig. 22). Heat both pieces and make sure that they are a snug fit (Fig. 23). Bring to a full-welding heat and weld together, beginning with a position where the smaller piece is driven down on to the longer one (Fig. 23). Additional hammering is then carried out, working alternately from each side (Fig. 24).

If necessary, take another welding heat and complete the joint, making sure that both scarfs are securely welded into a solid mass. Slightly bend the longer part (Fig. 25) and complete the finishing in the position shown. Forge to a square section first, remove corners and then finish to a round section with the hand hammer.

It is important that a well-pronounced radius be maintained at the junction of the two pieces to give it strength. Careful use of top and bottom fullers will help to form this radius and produce a neat finish. Top and bottom swages can be used to impart a better finish to the short arm after welding, but take care not to allow the edges of the swages to indent the radiused junction of the work.

Agricultural engineering in development


Agricultural engineering in development


Agricultural engineering in development


Agricultural engineering in development


Reheat to a bright red heat, cool the short arm with water (Fig. 26) and then, by holding on the anvil (Fig. 27) and applying hammer blows to the short end, the long back part can be straightened.

Next, mark off the required length for the bend at the end of the long piece and cut off any excess with a sharp hot set. The length will depend on the thickness of metal to be bent with this tool, but for this example it will be about 150 mm. Lightly centre-punch this position and then heat to a bright red heat, cool with water to restrict the heat to within about 15 mm each side of the mark, bend over the beak (Fig. 28) and finish (Fig. 29) in a bottom swage. The workpiece can now be finally trued up in all directions and allowed to cool in the air.

The space between the two short arms now formed must be larger than the metal upon which the tool is to be used. With a space of 40 mm, metal with a thickness of 10 to 20 mm can be handled. Only a few such tools are needed to cover a very wide range of metal sizes.

The hooked end shown in Fig. 21F is next to be formed. Take a near-welding heat on the end of the bar and forge a flat point. Keep the width of the point to approximately the same as the diameter of the bar. This end is then bent back over the handle (Fig. 21F) and closed tightly on the piece of the metal it is to fit.

To complement this tool, a fork can be made to fit into the tool hole of the anvil. These tools are often preferable to a vice for bending work since they are faster to use than moving from anvil to vice and back again. Bending dogs can be made of steel from 10-mm rod up to 25-mm bar for heavy work.

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