Upsetting

What upsetting does

Upsetting shortens a piece and makes it thicker or wider - the opposite of drawing out ¹. It makes stock for bolt heads, shoulders, collars, the eye area of a hook, extra material at a corner, and the thick end of a scarf before forge welding.

Control the heat

Bacon’s rule: the part of the work which is hottest will be upset the most ¹. So:

• Heat only the section you want thicker.
• To confine heat further, take a full heat and then cool the rest of the bar in the water bucket, leaving the end glowing ¹.
• Short pieces heated all over can be held in the middle and have their ends cooled one at a time ¹.

Technique

Ways to upset, depending on the work ¹:

1. On end: stand short work vertically on the anvil and strike the top end squarely.
2. Over the edge: lay longer work across the face with the hot end two or three inches past the edge and strike the end; heavy work resists the blow by its own weight, light work may need a sledge held against the cold end.
3. Ramming: drive the heated end against the anvil’s side or a heavy block.

Keep the bar straight. After a few blows it will want to bend; straighten it before upsetting further ¹, or it folds instead of thickening.

Blows and shape

• Light blows reach only the surface and ends, so a short bar upsets at the ends and stays thin in the middle (a dog-bone) ¹.
• Heavy blows with good heat push the effect deep, upsetting the middle more ¹.
• To even out a piece, heat and upset one end, then the other ¹.

Upsetting is slow and tiring. Use the highest heat the steel tolerates, and don’t try to upset more than about the stock’s own diameter in one go.

What to take from this

Upsetting makes stock shorter and thicker, and the hottest part upsets most, so localize the heat and quench the rest. Upset on end, over the edge, or by ramming; straighten the bar whenever it bends; and use heavy blows to upset the middle instead of just the ends.