The “donkey-head” tilt hammer

Sentences without a label are documented facts; the others are marked "probable" or "uncertain".

For centuries, in the valleys of the Orco, iron and copper were beaten with a machine driven by water: a channel, a wheel, a shaft with cams and a long wooden helve that acts as a lever for an iron head. This page takes the tilt hammer apart piece by piece, with the measurements of the forges that can still be seen, explains the mechanics that make it work and follows the road that leads from the tilt hammer to today's hot forging.

The water, the channel and the wheel

The tilt hammer needs the water that drives it: that is why forges and furnaces are built along watercourses, where diversions and drops can be made. In the mid-eighteenth century the intendant Rezia di Mombello writes that the Orco serves “for the use of the various forges and buildings” and the Soana “some forges and mills”.

The Canavet forge at Canischio, recorded by Cima in 1980, shows the complete installation. The intake weir is made of large river cobbles laid dry, in an inverted V, and holds back a basin of about one hundred cubic metres. The channel is about 200 metres long and gives a drop of about 3 metres: in its last stretch it runs higher than the level of the drives and ends on balconies of posts that carry the wooden flumes, each with its own sluice gate. At Castellaro the channel from the Soana is from 1.5 to 2.5 metres wide and on average 50 centimetres deep; at its end it divides between the trompes and the wheels with a drop of about 5 metres.

In the mid-eighteenth century the mills of the province of Ivrea all have a wheel with a horizontal axle, fed from above in the mountains and more often from below in the plain. At the Canavet there are both types. The wheel of the tilt hammers is “overshot”: made of iron by an engineering workshop, with two rims 2.25 metres in outer diameter, the shaped buckets between the two, eight pairs of spokes and a square hub of 70 by 70 centimetres; its form dates it to the nineteenth century. The grindstone, instead, turns on an “undershot” paddle wheel, called “a schiaffo” (slap wheel), which Cima estimates to be fast, about 200 revolutions per minute.

An overshot wheel works mainly with the weight of the water that fills the buckets on one side and goes down; an undershot wheel with the thrust of the current on the paddles. In the seventeenth and eighteenth centuries wheels with a stone hub appear, which acts as a flywheel and makes the motion more powerful and regular. At Castellaro the hub has an octagonal hole for the shaft and radial holes for the wooden blades, closed by rims that form the boxes into which the water falls. A flywheel is a rotating mass: it stores kinetic energy when the driving force exceeds the load and gives it back when the load increases, for example at the instant when the cam lifts the head of the tilt hammer.

Sources: Cima 2024, pp. 149, 193, 204; Cima 1987, pp. 43, 65; Cima 1981, pp. 170, 172-173, record cards 15CA, I01/15CA, I02/15CA, I03/15CA and M01/15CA; Cima 2025a, pp. 105-106

The camshaft

The drive shaft lies at right angles to the helve of the tilt hammer and carries a series of cams that strike its short end and suddenly lift the head. At the Canavet the shaft, the “arbul”, is a chestnut trunk about 40 centimetres in diameter and 5 metres long, bound with iron rings, with case-hardened and tempered steel pivots at the ends; each end rests on a large boulder, the “giradur”. The cams, called “rane”, are rings of steely cast iron 50 centimetres in outer diameter and 40 in inner diameter, with many rectangular holes into which forged steel teeth are inserted; they are fixed to the shaft with wooden wedges.

At Castellaro the two shafts have maximum diameters of 52 and 75 centimetres and lengths of 7.20 and 5 metres: the thinner one is the longer. Cima does not say which shaft goes with which battery. Four cams on a cast-iron collar give four blows at each turn of the shaft, and the cams of the different tilt hammers are staggered to alternate the loads. The pivots were lubricated with water brought by a small channel above the shaft. At the Giovando forge at Sparone, in the Thirties, the shaft was an oak trunk bound with iron, with two steel bands that carried the cams between the two tilt hammers. A battery carries up to three tilt hammers on the same shaft, with a single channel and a single wheel-and-shaft unit.

The cam turns the continuous rotary motion of the shaft into a reciprocating motion of the helve. The number of blows per minute of a tilt hammer is the number of revolutions of the shaft multiplied by the number of its cams. Staggering the cams of neighbouring tilt hammers means that the shaft does not have to lift all the heads at the same instant: the load on the wheel stays more even.

Sources: Cima 2024, pp. 192, 206, 209; Cima 1981, record cards C01/15CA, C02/15CA and F04/15CA; Cima 2025a, pp. 104-106; Cima 1987, p. 54

The helve is a lever

Cima calls the water-driven hammer “maglio a testa d'asino” (“donkey-head” tilt hammer) or “martinetto”, a machine that became established between the twelfth and the fourteenth century and remained in use for many centuries. In the oldest form, the tail hammer, the frame has two heavy uprights of stone, more rarely of wood, set into the ground and joined by two pairs of crossbeams.

The helve is a first-class lever: the fulcrum is on the frame, the short arm on the side of the cams, and the hammer head is fitted onto the long arm. The fulcrum is the “boga”, an iron collar with two opposed cones that rests on the uprights in metal bearings, more recently of bronze: at Castellaro the bronze plate is called “sciolino”. The boga sits about a third of the helve's length from the tail; at the tail a tooth, the “palmolino”, meets the cams of the shaft, called “palmole”. At the end of the lift the helve is thrown against a boulder or a spring, which makes it rebound and strengthens the fall. Under the hammer head there is the “dema” or “dama”, the large buried stone block that carries the anvil, the “azzarino”: it is also the main stiffening element of the whole tilt hammer.

The measurements change from one forge to another. At the Canavet the helve is a chestnut trunk 25 centimetres in diameter and about 2.3 metres long, the boga a steel ring of 30 centimetres and the hammer head a steel block of about 30 by 30 by 75 centimetres, from the Ceresa steelworks in Turin. At the Giovando forge, in the Thirties, the steel head weighed about 400 kilos and the helve was a walnut trunk about 4 metres long. According to Tylecote, quoted by Cima, the heads of ancient tilt hammers weighed about 100 kilos and those of the eighteenth century reached 400 probable.

In a first-class lever in equilibrium, force times arm is the same on either side of the fulcrum. With the fulcrum a third of the way from the tail, the arm of the head is about twice that of the tail: to lift the head the cam must push the tail down with a force about twice the head's weight, but a movement of the tail equal to half the height to which the head rises is enough.

Sources: Cima 2024, pp. 177, 198, 204, 206, 210-211; Cima 2025a, pp. 103-105; Bussi 2026, p. 57; Cima 1987, p. 54; Cima 1981, record cards C03/15CA, C04/15CA, U01/15CA and F02/15CA

Three forms of tilt hammer and the drop hammer

Cima distinguishes, using Bertrand Gille's terms, three forms of “donkey-head” tilt hammer: tail, side and front. The tail hammer is the oldest water-driven striking hammer and, together with the side hammer, it already appears in late medieval sources; the front hammer comes later. The side hammer, usually made entirely of wood, is the “German-style” hammer of Agricola's plates, with blows of little power; the front hammer has cast-iron load-bearing parts and a very heavy head, but in the Canavese Cima reports none.

The drop hammer (berta) is a different machine: a free-fall hammer. The head slides between two vertical guides and rises by winding a leather belt onto a pulley driven by water, when the worker presses a friction roller with the levers; it falls again when he releases it. The drop hammer forges the piece inside two-part dies of case-hardened and tempered steel, with a few blows, on the billet at white heat, about 1250 degrees.

Cima places the spread of drop hammers at the end of the nineteenth century, but he publishes a watercolour drawing of 1812 of the ironworks of the lawyer Signorelli at Cuorgnè, at Loreto, with a large drop hammer called “Berta” lifted by a water wheel uncertain.

Sources: Cima 2024, pp. 176, 194, 202, 205-207, 210, 214-216; Cima 2025a, p. 112

Regulating the blow

The tilt hammer was guided by an experienced forger, seated on a low stool, who with a lever near the head regulated the sluice gate and therefore the frequency of the blows; an assistant handed him the pieces. Bussi writes instead that two men worked at the tilt hammer, one at the piece and one at the lever. At the Canavet a wooden slide valve sends all the water onto the wheel, part of it or none: in this way it gives the tilt hammers maximum speed or intermediate speeds, or stops them. At Castellaro a gate at the end of the flume was moved by the hammerman with pantograph rods.

The Signorelli deed of division, in 1716, says it in the words of the time: once the water is opened, the tilt hammers “are seen to beat hard and subsequently little ... according as more or less water is put on them”. More water on the wheel means more torque and therefore more revolutions per minute, that is more frequent blows; less water, sparser blows.

Interchangeable steel tools for flattening, cutting or punching were fitted onto the tip of the hammer head probable. Shaping hot iron at the tilt hammer with successive blows is called “scapolatura”. How many blows per minute a tilt hammer of the valleys struck, the sources read do not say: Cima gives neither the blows nor the revolutions of the wheels uncertain.

Sources: Cima 2025a, pp. 72, 74, 105; Bussi 2026, pp. 27, 59; Cima 1981, p. 126, record card I05/15CA; Cima 2024, pp. 206, 210, 213

Around the tilt hammer: trompe, forge and grindstone

The forge fire needs air. The trompe (water-powered blower) is a vertical pipe fed from above by a flume: the water falls onto a stone inside a barrel immersed in the outlet basin, the air drawn in through slanting holes in the upper part of the pipe collects at the top of the barrel and goes to the fire through a blast pipe. It has no moving parts. At Castellaro the larger one has two wooden pipes made from trunks 4.20 metres tall, with four “nostrils”, and falls into a buried barrel 180 centimetres in diameter.

Before the trompe there were bellows, which were used in pairs to give a continuous blast; a mechanised bellows often cost more than the furnace. On the appearance of the trompe Cima gives different dates, from the end of the sixteenth century to the eighteenth; a trompe already exists at Ponte d'Invrea, in Liguria, in a valuation of 1619 or 1621 uncertain.

The forge of the Canavet is a hearth of refractory bricks on a stone base, for a charcoal fire. The grindstone is driven by a small undershot wooden wheel, and a flat leather belt between two pulleys doubles its revolutions. The cycle of a hoe shows how everything fits together: a piece is cut from the billet at the tilt hammer, heated in the forge to orange, about 950 degrees, roughed out at the tilt hammer, and the process is repeated; then it is finished at the anvil and the grindstone and quenched in water or oil.

In the trompe the falling water carries with it the air drawn in through the holes; in the barrel the air separates from the water, which flows out below the surface of the outlet and keeps it sealed, and finds as its only way out the pipe towards the fire.

Sources: Cima 2024, pp. 137, 217-218, 222-225; Cima 1987, pp. 54, 56; Cima 1981, pp. 174-176, record cards I04/15CA, F03/15CA, M02/15CA and C05/15CA; Cima 2025a, pp. 100, 102

From the tilt hammer to die forging

The structure of the forges is mature in the sixteenth century and until the nineteenth no new machines arrive: only the dimensions grow, with higher water drops, very heavy stone hubs and larger wheels. For Cima the Canavet went on producing “as if the industrial revolution were a matter for another continent”. Cima explains it with the machine itself: with three tilt hammers on the same shaft, the forge could triple its output just by adding workers; that is why it was never modernised, until it could no longer withstand the competition.

In the Gallenca valley, however, the transition did take place. The San Colombano mill, the Ravetto, around the Twenties of the twentieth century became, with the Rolle family, a water-powered mechanical forge and then a hot forging (closed-die) workshop for steels that uses the same water drop. So too, before 1980, did the Batassa forge at Prascorsano. The Uzane forge at Valperga, with a “donkey-head” tilt hammer, passed in 1875 to the Varzino family, who turned it into an engineering workshop still active in 1980.

Hot forging (closed-die) deforms the heated piece by closing it between two dies that have its shape, instead of shaping it blow after blow as at the tilt hammer. The drop hammer, which forged the billet at white heat inside two-part dies, is the point of contact between the two techniques.

In 2013 the Region calls the area between Castellamonte, Cuorgnè, Rivarolo and Ciriè “the system of hot forging and car parts in the Western Canavese”, where hot forging of steel and car parts remain the prevailing sectors. That today's die forging descends in part from the water-driven forges is documented only for the Gallenca valley; for the forges of the Orco a direct link is not documented probable. Nor is it known whether magnins or forgers from the valleys worked in the first forging workshops, nor how many firms and workers there are in forging today: the sources read do not say uncertain.

Sources: Cima 2024, pp. 192, 204-205, 214-215; Cima 1981, pp. 127, 167, 169-170, record cards 08SC, 09PR and 03VA; Regione Piemonte 2013, p. 6; ISTAT 1971, p. 103

For the class

A calculation to try. At the Giovando forge the head weighed about 400 kilos, the helve was about 4 metres long and the fulcrum was about a third of the helve's length from the tail. Neglecting the weight of the helve, what force must the cam exert on the tail to hold the head up? If the head must rise by 30 centimetres, by how much must the tail go down? Solution: the arms measure about 1.33 and 2.67 metres, so the force is about twice the weight of the head, the weight of about 800 kilos; the tail goes down by about 15 centimetres. The height of 30 centimetres is an assumption of the question: the sources read do not give the height of the fall.

Second question. At Castellaro each collar carries four cams and gives four blows at each turn of the shaft. The sources read do not say how many revolutions per minute the wheels made: choose a plausible value, calculate the blows per minute and discuss how they would change if the sluice gate were opened wider. Third question: what would happen to the shaft and the wheel if all the cams of a battery lifted the heads at the same instant?

Sources: Cima 1987, p. 54; Cima 2025a, pp. 104-105; Cima 1981, record card C02/15CA