Shaping Metal With Intent: The Upset Technique
Upsetting—thickening steel by shortening it—is one of the most misunderstood forging techniques. When done correctly, it allows you to add mass exactly where you need it, strengthen weak areas, and shape metal without adding welds or extra material. When done incorrectly, it causes cracking, mushrooming, tearing, or buckling that ruins the workpiece.
This post will walk you through when to upset steel, why the method is so useful, and exactly how to do it without cracking or deforming your piece.
What Is Upsetting?
Upsetting is the process of increasing the cross-sectional area of steel by compressing it lengthwise.
In simple terms: you make the steel thicker by making it shorter.
Examples include:
Thickening a bar end for a hammer or axe eye
Adding mass for a tenon or rivet head
Preparing stock for punching or drifting
Creating decorative terminals (balls, knobs, and forged ends)
Strengthening transition points in tools
Upsetting is one of the oldest forging techniques, and still one of the most valuable.
When Should You Upset Steel?
Upsetting is the right choice when you need more mass in a specific location without welding additional material. Here are the most common situations:
1. Creating Tool Heads (Hammers, Hatchets, Top Tools)
You may need extra thickness to punch an eye or create a sturdy peened end.
Upsetting builds:
More material around the eye
Strength and durability
A balanced mass distribution
2. Prepping for Punching or Drifting
Punching a thin section leads to distortion or tearing.
Upsetting solves this by giving you more material to work with.
Perfect for:
Hammer eyes
Hardy tools
Chisels
Top tools
3. Making Decorative Ends
Many blacksmiths upset ends to create:
Balls or knobs
Tapers with bold shoulders
Finials or architectural elements
Square-to-round transitions with strong shoulders
4. Strengthening Weak Points
If a section needs reinforcement (like the tang of a tool), upsetting creates a thicker transition area without adding welds.
5. Correcting Mistakes
Did you draw something out too thin? Upsetting can recover the stock—as long as it isn’t overworked or cold-short.
Why Upsetting Causes Cracks (and How to Avoid Them)
Upsetting stresses the steel because you’re forcing it to compress.
Cracks appear mainly from:
Too low of a heat (steel isn’t plastic enough)
Overworking the surface (scale crusts crack the surface)
Cold shuts formed by folding edges during compression
High-carbon steel brittleness
Forcing the steel off-axis, causing buckling or uneven mushrooming
Good upsetting is all about heat, alignment, and accuracy.
How to Upset Steel Properly (Step-by-Step)
Below is a simple, reliable method used by professional smiths:
Step 1 — Heat the Steel Correctly
Use a bright yellow to light orange heat (higher for high-carbon steels).
Temperature guide:
Low carbon: Bright orange
Medium/high carbon: Bright orange to yellow
If it’s too cold, the steel will crack almost instantly.
Step 2 — Keep the Piece Straight
Hold the bar perfectly vertical on the anvil.
This ensures the steel compresses evenly and doesn’t buckle.
If the bar leans, you'll force the metal sideways and cause mushrooming or tearing.
Step 3 — Strike the End, Not the Sides
Use controlled blows directly to the end of the bar.
Hammer types:
Flat face for general upsetting
Slightly crowned hammer for clean compression
Rounding hammer for larger, smoother movement
Avoid striking the sides of the upset area until you're ready to shape it.
Step 4 — Flip, Reheat, and Repeat
Upsetting usually takes several heats.
Take your time and don’t force cold steel.
Each heat:
Upset the section
Straighten the bar if necessary
Reheat before it cools past orange
Step 5 — Shape and Clean Up
After reaching your desired mass:
Use the flat face to square or round the shape
Dress the shoulders
Remove any bulges with strategic side blows
At this stage you’re not upsetting anymore—you’re sculpting.
Pro Tips for Crack-Free Upsetting
Use short heats
Heat only the area you want to upset.
Cold steel below the heat zone resists movement and causes cracking.
Add a slight chamfer before upsetting
Breaking the edges slightly prevents cold shuts as the steel mushroom expands.
Keep your blows controlled
Wild hammer swings increase buckling risk.
Use the anvil horn to support curved pieces
If the bar isn’t straight, the horn provides better vertical alignment.
Normalize between heavy heats
For high-carbon steel, normalizing prevents internal stress buildup.
Watch for folds or seams
If you see a crease forming, isolate heat and planish it out before continuing.
Common Upsetting Mistakes (and Quick Fixes)
Mistake: Working too cold
Steel cracks, crumbles, or folds.
Fix: Reheat to bright orange/yellow before continuing.
Mistake: Bar bends instead of thickening
This means it wasn’t vertical or wasn’t heated long enough.
Fix: Straighten immediately while hot, then continue.
Mistake: Mushrooming at the edges
You didn't chamfer or weren’t centered.
Fix: Trim or forge the edges back in, then continue upsetting.
Mistake: Upset area tears or breaks
High-carbon steel overheated or worked at too low a temp.
Fix: Normalize, then try again with better heat control.
Final Thoughts
Upsetting is one of the most powerful techniques in blacksmithing when you understand how to use it. It allows you to move mass efficiently, strengthen critical areas, and create shapes that can’t be achieved by drawing out alone.
The key to success is:
High heat
Straight alignment
Controlled hammering
Patience over brute force
Mastering upsetting will dramatically expand what you can create—from tools to decorative ironwork to blades and structural hardware.
If you would like to discuss a potential project with us, please do not hesitate to contact us.
