What Is Upsetting?
While drawing out moves metal lengthwise to make a bar longer and thinner, upsetting does the opposite: it compresses metal to make it shorter and thicker. If you need to add mass at the end of a bar, create a pronounced shoulder, form a rivet head, or bulk up material before working it into a particular shape, upsetting is the technique to reach for.
It sounds simple — and the concept is — but executing a clean upset without buckling or going off-center requires attention to heat management and technique.
When Do You Need to Upset?
Common situations where upsetting is the right move:
- Creating a head on a rivet or bolt blank
- Building up material at the base of a tenon before cutting the shoulder
- Thickening the cutting edge area of a tool before grinding
- Forming a collar or boss on a bar
- Creating an integral head on a handled tool like a hammer or hatchet eye
The Basic End Upset
The simplest upset is performed on the end of a bar. Here's the process:
- Heat only the area you want to upset. This is critical — if the entire bar is hot, the compression will cause it to buckle randomly. Heat only the last 1–2 inches for an end upset.
- Get a proper forging heat — bright orange to yellow-orange. Upsetting requires significant force, and the metal must be soft enough to move without cracking.
- Strike the end of the bar directly on the anvil face — dropping it vertically onto the face, or striking the far end with a hammer if it's short enough. The impact drives metal upward and outward, thickening the heated section.
- Straighten frequently. Even a slight bend in the bar will cause it to buckle rather than upset cleanly. After every few blows, check that the bar is straight and correct any bend immediately while the metal is still hot.
Controlling the Upset: Heat Gradient Is Everything
The single most important factor in clean upsetting is controlling exactly where the metal is hot. Steel moves where it's soft — which means it upsets where it's hottest. This gives you powerful control:
- To upset only the very tip of a bar, heat just the last half-inch intensely.
- To upset a mid-section, heat that section and keep the rest of the bar cooler (wet the cool areas if working in a coal forge, or pull from the propane forge quickly).
- To create a shoulder at a specific point, heat right up to — but not beyond — where you want the shoulder.
Using a tight heat zone gives you precision. Sloppy, diffuse heats produce unpredictable upsets that travel along the bar rather than concentrating where you need them.
Upsetting in a Vise (Cold Heading)
For smaller stock and near-final shapes, you can upset the end of a heated bar by gripping it in a post vise just below the heated section and striking the end with a hammer directly. The vise acts as a backstop, concentrating all force into the upset section. This is sometimes called vise upsetting and gives you excellent control over where the mass builds up.
Troubleshooting Common Problems
| Problem | Likely Cause | Solution |
|---|---|---|
| Bar buckling in the middle | Heat too diffuse, bar too long without support | Tighten heat zone; support longer bars in vise |
| Upset going off-center | Bar not perfectly straight before striking | Straighten bar first; check alignment each heat |
| Fins or folds appearing | Metal cooling during upsetting, laps forming | Work hotter, move faster, work more heats |
| Little movement despite hard blows | Steel too cool | Return to fire; work only at bright orange or above |
Upsetting and Drawing Out Together
In practice, upsetting and drawing out are complementary skills that are often used in sequence. A common workflow for making a handled tool might be: upset the end to build mass for the head, then draw out the handle section to the desired length and taper. Understanding both operations — and when to use each — gives you complete control over the mass distribution of your work.
Practice upsetting on scrap mild steel in 1/2" and 3/8" round or square stock. Focus on keeping your heats tight and your bar straight. The more you do it, the more predictable and satisfying the result becomes.