Set the anvil face at the height of the smith’s knuckles with the arms hanging, on a base that cannot move, within 1.5-2 m of the forge according to the workshop guide or one step according to the forge setup guide. A freely moving 20 kg anvil under a 1 kg hammer turns about 5% of each blow into motion of the anvil, and a 50 kg anvil only about 2%, so mass and a fixed base are what put the hammer’s energy into the hot metal.
Part of Workshop & Forge Design
The anvil is the hard, heavy block on which hot metal is hammered, and its height, distance from the fire and mounting decide how much of each blow reaches the work.
Mass And A Fixed Base Decide How Much Of The Blow Reaches The Metal
The workshop guide puts the anvil 1.5-2 m from the forge on the smith’s dominant-hand side, at knuckle height with the arms at the sides, on a hardwood stump (oak or elm) set into the ground or on a heavy stone base. The forge setup guide asks for the anvil within one step of the forge, and for a railroad rail section of 15-30 kg as the smallest workable improvised anvil (Forge Setup). Its rule is that the anvil must not move or flex.
The two distances disagree, and the choice is a trade. The shorter distance means less time between fire and anvil, while the piece is at working heat. The longer distance keeps the smith’s body out of the forge’s radiant heat and leaves room to swing a hammer and turn long bars. Pick one in the range between them and mark it; then do not move the anvil.
Worked Example: Energy Lost To A Moving Anvil
A simplified model: the hammer (mass m, speed v) strikes the workpiece on a free anvil (mass M) in a perfectly inelastic collision. Momentum is conserved, so the combined mass moves off at V = m × v ÷ (m + M), and the energy left in that motion is the fraction m ÷ (m + M) of the blow. The rest, M ÷ (m + M), is available to deform and heat the metal.
| Hammer | Anvil | Energy lost to motion | Energy to the work |
|---|---|---|---|
| 1 kg | 5 kg | 1 ÷ 6 = 17% | 83% |
| 1 kg | 15 kg (smallest rail) | 1 ÷ 16 = 6% | 94% |
| 1 kg | 20 kg | 1 ÷ 21 = 5% | 95% |
| 1 kg | 50 kg | 1 ÷ 51 = 2% | 98% |
| 2 kg | 20 kg | 2 ÷ 22 = 9% | 91% |
The hammer masses are illustrative. Real anvils sit on a base, so this energy is absorbed by the stump and the ground rather than returned to the hammer; the model shows the trend, not a measurement. Heavier hammers need heavier anvils, and a block that rocks wastes more than the table shows.
What You Need
- An anvil or substitute: 50-150 kg for a proper anvil, 15-30 kg for an upright rail section or a thick steel plate (forge setup guide)
- A base: a hardwood stump set in the ground, or a heavy stone block
- A way to hold the anvil to the base: iron staples, straps or spikes driven into the wood
- A tape or a stick to measure the smith’s knuckle height
Method: Height, Distance And Mounting
Step 1: Measure knuckle height. The smith stands upright with the arms hanging. Measure from the floor to the knuckles. As an illustration, take 75 cm.
Step 2: Work out the base height. Base height = knuckle height − height of the anvil from its foot to its face. If the anvil stands 45 cm tall, 75 − 45 = 30 cm.
Step 3: Fit the stump. A stump 70 cm long with its top 30 cm above the floor is buried 70 − 30 = 40 cm. Set the end grain down, tamp earth around it in layers and check that the top is level with a water level or a straight edge.
Step 4: Secure the anvil. Fix it so it cannot jump or walk. At this point a hard blow should produce a ringing note, not a dull thud and no movement.
Step 5: Fix the distance. Choose a distance between one step and 2 m, clear the floor around it for the swing, and leave an unobstructed route to the quench tank (Quench Tank & Water Access).
Common Mistakes
- Wood buried to rot. Untreated softwood buried in the ground rots in 3-5 years (the fortification guide gives that figure for pine and spruce posts), and charring the buried part extends its life (Fortification Materials). Set the anvil on stone to avoid the problem.
- A stump left smouldering. Hot scale and dropped pieces char a wooden base. Check it at the end of every session, and do not leave a hot piece resting on it.
- An anvil too high or too low. The forge setup guide: too high strains the wrist, too low the back.
- Using the anvil as a chopping block or welding table. Cutting into the face ruins it.
Safety
Hot scale, chips and noise
Hammering throws scale at forging heat and can chip the hardened face of the anvil or the head of a hardened hammer. Wear eye protection and a leather apron, keep bare legs and feet clear, and never strike two hardened tools together. Hammering on an anvil is loud enough to damage hearing over years; plug the ears. A wooden base near a forge is fuel, so keep the 200 L water barrel within reach (Fire Safety & Suppression).
What’s Next
- Learn next: Quench Tank & Water Access — the next station in the line
- Combine with: Metalworking — what the anvil is used for