History of Steelworks' Plant and Equipment
This page contains some technical history of open hearth furnaces, rolling mills and shears, of the type used at Clydebridge. Much of the information is based on excerpts from Technical Papers written by Mr Thomas Brown MacKenzie, MIMechE, Chief Engineer of David Colville and Sons, between 1894 and 1924.

Contents :

The rapid advance of mechanical engineering in the latter part of the eighteenth and in the nineteenth centuries accelerated the progress by placing better and more powerful machinery at the disposal of the Ironmasters, whilst at the same time creating a demand for Iron.

Important dates are 1728, when Payn and Hanbury introduced their Rolling Mill for the production of Sheet Iron; 1760, when Smeaton substituted Cast Iron blowing tubs for the wooden and leather bellows previously in use; and 1783, when Cort introduced grooved rolls for Merchant bars. Most important of all, however, were the introduction of the steam engine at the end of the eighteenth and beginning of the nineteenth century, of the railroad about 1825, and the invention, by Nasmyth, of the steam hammer in 1838.

The next important invention was at Clyde Iron Works, in 1828, when J. B. Neilson invented the process of heating the blast. This greatly improved fuel economy, although the blast was at first heated by burning raw coal in the stoves; but in 1832 the work of heating the blast was done by the waste gases at Wasseralfingen in Bavaria; and this method was then universally adopted.

The First "Open Hearth"

The Open Hearth furnace owes its inception to the brothers Frederick and William Siemens.

In a lecture which Mr. C. W. Siemens, F.R.S . (later Sir William Siemens) delivered at a meeting of the Chemical Society in 1868, he presented many interesting facts about the early history of the manufacture of Steel in the Open Hearth Furnace. Heath, the discoverer of the beneficial action of Manganese, was the first, he said, to make the attempt in 1845. His method was to melt pig-iron in a cupola, and transfer it in the molten state to a reverberatory furnace. Wrought iron scrap was introduced at another part of the furnace, between the bath of molten metal and the chimney, to be preheated before being pushed amongst the molten pig metal. "Fearing the effect of the ashes from a common fire-place, Heath proposed to heat his furnace by jets of gas; and there is every probability that his experiments would have been successful if he had possessed the means of imparting the intensity of heat to the flame, and at the same time the absence of cutting draught, which are essentially necessary."

Early Experiments - and Failures

After referring to other earlier experimenters, Mr Siemens comes to the Regenerative Gas Furnace invented by his brother, but developed and improved by the brothers jointly; a licence to use this was granted to Mr. Charles Attwood, in 1862, but he failed to make good steel on the Open Hearth and converted the furnace for heating crucibles. A licence was next granted to a French firm, Messrs Boigue, Bambour & Co, to erect a furnace in their works at Montlucon for a process devised by M Le Chatelier, but which did not turn out very well; upon which the company became discouraged and gave up the attempt, although, as Siemens pointed out, they had a very powerful furnace and one which would have done all that was required if the company had displayed the least determination to succeed.

Meanwhile, a licence had been granted to Emile and Pierre Martin, of the Sirenil Works in France, to melt steel both in crucibles and on the open hearth; and they built a furnace in 1864, chiefly intended as a heating furnace but, having been built of Dinas bricks, it was also available as a melting furnace. Siemens continued,

"With this furnace, which was really less suitable than those previously erected, MM Martin have succeeded in producing cast-steel of good quality and various tempers; and their produce was awarded a Gold Medal at the great French Exhibition of last year (1867). MM Martin have since patented various arrangements of their own, such as the employment of particular fluxes to cover the surface of the molten metal, the application of a separate furnace for heating the iron before charging it into the melting furnace, and the employment of particular brands of cast and wrought-iron which may be useful under special circumstances, but which form no essential part of the general solution of the problem."

Siemens' Sample Steel Works

Siemens went on to say that "Having been so often disappointed by the indifference of manufacturers and the antagonism of their workmen, I determined in 1865 to erect experimental or 'Sample Steel Works' of my own at Birmingham, for the purpose of maturing the details of these processes before inviting manufacturers to adopt them. The first furnace erected at these works is one for melting the higher qualities of steel in closed pots, and contains 16 pots of the usual capacity. The second, erected in 1867, is an open bath furnace, capable of melting a charge of 24 cwt, of steel every 6 hours."
"Although these works have been carried on under every disadvantage, inasmuch as I had to educate a set of men capable of managing steel furnaces, the result has been most beneficial in affording me an opportunity, of working out the details of processes for producing cast-steel from scrap-iron of ordinary quality, and also directly from the ore, and in proving these results to others."

Rolling Mills
Rolling mills have been used, in association with slitting mills since the 1590s for producing iron strips. Early rolling mills were small and water driven, such as the one still in existence at Wortley Ironworks Lower Forge in Sheffield.

Wider iron sheets, for making tinplate, were produced by John Hanbury in about 1720, and in 1784 Henry Court (of puddling furnace fame) was using grooved rolls to produce round and other sections.

In 1781 Matthew Boulton suggested, when on a visit to an ironworks in Wales, using a steam engine for driving a rolling mill, and on his return home he had a coupled steam engine made and connected to a forge train. This was adopted for the first steam driven rolling and slitting mill by John Wilkinson, in collaboration with Boulton and Watt, at his Bradley Works. It was driven by an engine that Watt invented with two cylinders and two beams, astonishing the other ironmasters, and was the forerunner of numerous other mills in his own works, and in those of envious rivals who followed this enterprising pioneer.

For many years after this it was the practice to have a Beam Engine, either condensing or non- condensing, in the centre of the mill, driving, a line of shafting from which mills were driven, these being situated right and left of the engine.

As mills became more powerful the central drive was found to be a disadvantage: for one thing, if anything went wrong either with the engine or the line shafting, the whole works was stopped. Accordingly it became the practice to drive the mills individually, and Horizontal Engines displaced the old Beam Engines.
With the advent of steel and the handling of heavier pieces, the individual drive became an absolute necessity.
For the earlier continuously rotating mills, engines with fly wheels could be used. The advantage of the fly wheel is that it stores energy at periods when little work is being done (as for example, when the piece is being passed back over the top of the rolls) which it can give out again when the maximum demand for power occurs - that is, when the piece is in the rolls. In this way the engine cylinders only require to be designed for something slightly over the average power required.

With a view to avoiding the loss of time while the piece was being passed back over the top of the rolls, Mr. James Naysmith (inventor of the Steam Hammer in 1838), suggested the use of Reversing Engines.
This was tried at Crewe and found satisfactory, with the result that the standard drive for reversing Rolling Mills, became either a two or a three crank Reversing Engine. It was of course impossible to use a fly wheel with these engines, as there was no reserve of stored energy to draw upon to take the peak loads; with the result that the cylinders had to be made large enough to take the maximum load. Thus the engine was running well under its' power for most of its time, which did not make for economy. Such engines were therefore referred to as "steam eaters."

For heavy plates the reversing mill has many advantages, and it was obvious that if it could be driven by an engine provided with a fly wheel to store energy, and give it out at the peak loads, considerable economy in steam, and fuel, would result.

Attempts were made to do this by the use of trains of gearing and clutches. The upkeep and breakage were, however, so serious as to more than absorb any saving in fuel; and so the less efficient but more reliable reversing engine held the field.

The problem of obtaining a more efficient drive for the reversing mill still remained open; and it was the A E G Company of Berlin that solved the problem using the Ilgner system of electric driving.
The first mill to be so driven was at the Hildegardehutte Works in Austrian Silesia. This was a large bar mill having four stands of housings, the rolls being 29 inch diameter. The mill was originally driven by a twin reversing engine. On a vacant piece of ground beyond the engine the electric plant was erected. It consisted of three DC motors in series, mounted on a shaft connected through an intermediate shaft, which took the place of the engine crankshaft. These motors had a normal capacity of 3,000 HP and a maximum of 10,350 HP and were capable of running at 120 RPM. The fly wheel converter set consisted of a three phase motor in the centre of 1,500kW normal and 4,300 kW maximum operating on a 3,000 Volt circuit at 50 Hz. On each side of the motor was a flywheel 13 ft in diameter, weighing 26 tons, and beyond these two variable voltage generators in series, each of 1,500 kW normal and 4,300 kW maximum rating.
The whole equipment was built on the most liberal proportions and was able to take momentary overloads of 200 per cent., to run for half-an-hour with 75 per cent, and for two hours with 40 per cent overload. The cost of the whole equipment was said to have between twenty and twenty two thousand pounds British money.

The manufacture of rolls for mills became wide spread in the latter half of the 1800's. The first company in the UK set up specifically to make rolls was the Guest and Cranage, Victoria Roll Foundry, in England in 1854. In 1857 R B Tennant Ltd set up a foundry in Coatbridge for roll making.

Slabbing / Cogging Mill

In Clydebridge the Cogging Mill was also referred to as the Slabbing Mill. Apparently Cogging Mill is a British term and Slabbing Mill is the American term. Before these mills came into use, ingots were converted into slabs for the rolling mill using Naysmith type Slabbing Hammers. Dalzell works started out with 2 Slabbing Hammers and when the Cogging Mill was installed it allowed larger ingots to be used, and it also greatly speeded up production.

The term Cogging may refer to the use of gear teeth (cog wheels) for the mill drive but is more likely to be derived from tilt hammers, which were also operated by cogs which lifted the helve hammer to allow it to drop back down on the piece being worked.

Cogging Mills were first used in a blooming mill at Dowlais in Wales in 1866 and were in use.in America, at Cambria, in 1871. The first universal cogging mill was that of James Riley, General Manager of the Steel Company of Scotland, at Blochairn Works in Glasgow, in 1884. In this mill slabs were turned up on edge for rolling their sides.

A second heavier cogging mill was designed for Blochairn in 1890 to embody improvements suggested by James Riley. Up to that time the widest slabs made did not exceed 36 inches. This new cogging mill was designed to produce armour plates up to 5 foot wide with finished edges to minimise further machining. It was decided not to turn the slabs up on edge, as the tilting gear was cumbersome and expensive, and the mill was designed as a Universal Mill, with two vertical rolls, for rolling the slab sides, in addition to the usual horizontal rolls. One of the vertical rolls moved across the mill to allow slab widths of between 32 inches and 60 inches to be worked along the edges. This mill dispensed with live-roller gearing for moving the slabs to and from the mill, using instead dead rollers and a hydraulically actuated pusher carriage, whose stroke was multiplied by chains and pulleys. The mill was controlled by five people, one at the screwing gear, one at the pusher carriage, one at the mill engines, with an assistant for the necessary oiling etc., and the roller in overall charge of the mill.

James Riley became General Manager of the Glasgow Iron and Steel Company in 1894, at which time a new cogging mill was built for the Wishaw Steel Works of the company. This cogging mill was built by Messers Lamberton & Co, with rolls 8 feet 6 inches wide and 40 inches diameter, with end grooves for rolling slabs up to 54 inches wide tilted up on edge. The mill was driven by a pair of steam engines with cylinders 46 inches diameter by 60 inches stroke. The mill also had a pair of steam engines driving the screw down gear for setting the mills roll gap draught. A further steam engine (9 inch cylinder and 15 inch stroke) drove the live geared rollers carrying the slabs into and out of the mill.

Slab Shears

James Riley used water hydraulic powered slab shears for both of the Blochairn cogging mills. These shears were made by Messers Tannentt, Walker & Co, of Leeds. The second, 1890, Blochairn slab shear had a bed plate and cast steel entablature with four corner columns and three hydraulic cylinders, two of 22 inches at the sides and a centre cylinder 31 inches diameter. A further ram held down the slab during shearing. A weight loaded hydraulic accumulator provided a pressure of one ton per square inch. The pipe work was all lead to a position to allow one man to control the shear.
Also about this time Messers Lamberton & Co designed steam slab shears for David Colville & Sons Dalzell works, to cut slabs 60 inches wide by 12 inches thick. The drive was provided by coupled steam engines driving an eccentric shaft shearing motion through reduction gearing.
An important consideration for slab shearing was the speed of shearing, because if the blades remained in contact with a hot slab for too long they would loose their sharp edge, necessary for making a clean cut.

Pull-Over Mill
Plate mills have been constructed in several types such as Pull-Over Mills, Reversing Mills, 3-high Mills, 4-High Mills, Universal Mills.

Early rolling mills (pull-over mills) had two work rolls that were driven by a water wheel, and later by steam engine. As the mill rotated continuously in one direction the plate was rolled through the mill then hand fed back over the top roll, to the rollers side of the mill.

At the British great Exposition in 1851 the Consett Iron Company displayed a plate 20 feet long, 3 1/2 feet wide and 7/16 inch thick. This weighed 1,125 pounds and was considered the largest plate rolled up to that time.

Reversing Mill

The first reversing plate mill was at Parkgate works, and it rolled the plates for I K Brunel's "Great Eastern" in 1854.

Pull-over difficulties were encountered by J Ramsbottom, Chief Engineer to the London and North Western Railway Co, who wanted to make the frame plates of locomotives all in one piece, but the handling of long plates was difficult at a pull-over mill and the time taken allowed the plates to cool and reduced the output of the mill. He mentioned the problem to Mr Naysmith, the inventor of the steam hammer, who suggested reversing the mill, so that the plates would not have to be lifted and could be worked in both directions, thus doubling the output of the mill. To test the practicality of this, Mr Ramsbottom placed a pinion on the driving axle of a locomotive, geared to the mill in such a ratio that when the locomotive was running at the rate of 60 miles per hour the mill was at its normal rolling speed. The experiment proved quite successful, in spite of prophesies by the practical men at the mill that it would be impossible to roll plates without a fly wheel, with the result that a reversing engine was made with 36 inch steam cylinders, and set to work in 1866. This arrangement worked from the start without a hitch.

On the 4th December 1866 James Naysmith received the following letter from Mr Ramsbottom:

"Dear Sir - I must crave your forgiveness for my great delay in acknowledging the receipt of your kind letter of the 29th August, in which you refer to the successful carrying out at these works of your idea of a 'Reversible Rolling Mill without a Fly-wheel.' It has long been to me a matter of astonishment that your idea has not been reduced to practice years ago, particularly when it is considered how well the arrangement is adapted to the rolling of Armour Plates, or other work requiring a sustained effort, whilst it is at the same time more effective than the ordinary mill arrangement for very light work. So much is this latter true, that the men who are left to their own choice in the matter, will reverse the mill rather than pass a light sheet of 8 or 10 lbs. weight over the upper roll. This country is much indebted to you for so valuable a suggestion; and now that it has been brought to a successful issue, I have no doubt but it will be widely acted upon. I need not add that it will afford me much pleasure to show you the mill, and also what we are doing generally, if you should at any time visit Crewe."

James Naysmith also passed on the invention to Mr. Thomas Gillott of the Farnley Ironworks, Yorkshire, and received from him the following letter, dated the 2nd January 1877:

"Dear Sir - I was much gratified to see by your letter in Engineering the interest you have shown with respect to the large Reversing Plate Mill erected by me at these works, and drawn on the plan suggested by you. Allow me to thank you for the complimentary manner in which you have mentioned my work. Since the notice appeared, we have done a deal of heavy work in this mill; and a plate large enough to shear 11' 0" and 10' 2" and 1/2" thick has been rolled in five minutes. The slab went through the roll 17 times before being rolled to the width and turned round, and 18 times after turning and of the full width; making a total of 35 passes--the turning occupying 20 seconds. When it is remembered how rapidly a thin plate cools, this performance will sufficiently indicate the severe work this mill is capable of doing; notwithstanding the many predictions that such large plates could not be rolled without a fly-wheel. As to repairs, none have been required; so I cannot compare this with the Clutch systems. In respect of steam used, the direct acting engines compare favourably with an expansion beam condensing engine doing similar but lighter work. Should it ever be your wish to see this mill at work, I should be much pleased to have the opportunity of showing it to you.

Although Naysmith's reversing mills, with direct-acting engines, fitted with link-motion and without fly wheels, had been proved satisfactory, there was still a prejudice against them in many places. They were accused of being "steam eaters", which they were. There was also a disinclination to scrap engines which were in good condition, so reversing the mills by trains of gearing was tried.

At the Glasgow meeting of the Iron and Steel Institute, in August, 1872, under the Presidency of Mr (afterwards Sir) Henry Bessemer, two papers were read describing reversing gears for Rolling Mills : one by Mr R. D. Napier of Glasgow and the other by Mr. Graham Stevenson of Airdrie. Both used friction clutches, which were no doubt a great improvement on positive claw clutches. Several reversing gears of these and other types were made and used in various parts of the country; but it was soon found that the wear and tear of the gearing, together with the frequent breakdowns, were causing greater loss than the extra steam used by the reversing engines; and they soon became obsolete.

The early plate mills tended to have two, or more, stands. The first stand was a roughing mill, and usually both the top and bottom roll were driven. The second stand was a finishing mill and usually only the bottom roll was driven. This was to avoid slip between the rolls, damage to the plate, and wear on the rolls and pinions if the rolls were not perfectly matched in diameter. A consequence of this, in fast running reversing mills, was that the free top roll would continue running, as a flywheel of stored energy, and could cause severe shock loadings through contact with the work piece as it re-entered the mill in the reverse direction. One partial solution to this problem was to fit a brake to the end of the top roll, however, even if stopped the top roll had still to be brought rapidly up to speed to match the already turning bottom roll during initial contact with the work piece. Another solution was to fit a light clutched drive to the top roll that would allow slip to take place.

The rolls fitted to the mills are subject to severe loadings and require a hard surface but a tough core. The initial roughing stand was usually fitted with grain cast iron 'soft' rolls and the finishing stand with chilled cast iron 'hard' rolls. Later, alloy cast steel rolls were used in the roughing stands.

The engine, initially usually a beam engine but later usually a horizontal twin compound engine, was located between the stands, driving a line of underground shafting, on which were mounted pinions to drive the several mills. The slabs / plates were hand manipulated through the rolls onto hand bogies or dead (undriven) roller tables. The roller table could be moved across between the hard and soft roller stands.

Incidentally, the Kelham Island Museum in Sheffield holds the largest remaining steamed engine in the UK - the1905 River Don Steelworks 12,000 horsepower vertical three cylinder armour plate rolling mill engine. To see this almost silent monster move is to see raw power and to see it instantly go into reverse is astonishing. A quote from the oldenginehouse web site says it all - "If you only ever see one steam engine moving in your life this should probably be the one!"

The early reversing mills were without live rollers, or indeed, any mechanical appliances for handling the material being rolled. A bogie on each side of the mill operated by men received the plate after each pass. With the increasing size and weight of plates this method became increasingly unsatisfactory, and steam-driven live roller racks were then introduced. The rollers at the back of the mill were at first mounted on a travelling carriage which, when the plate was sufficiently reduced in the soft rolls, could be moved across with the plate on it to the hard rolls. This arrangement was abandoned on most mills by the 1920s in favour of individual racks for each stand of rolls; the piece being transferred from the soft to the hard rolls by some form of pull-over gear. The racks and other auxiliary gear were also being electrically driven.

US / UK Trends 1895
At a presentation made by James Riley at the Institution of Mechanical Engineers, in July 1895, comparisons were made between British and American practice for plate mills. Most American plate mills were three high mills; that rotated constantly in one direction with the plate passing under and over the centre roll in successive passes through the mill. American plates were rolled in these mills direct from flat ingots cast from the bottom (although a cogging mill was used at Carnegie's Homestead works). In Britain this had been tried in the late 1880s but was abandoned in the belief that the Lloyds and Board of Trade tests could not be assured without the preliminary working to improve steel properties in a cogging mill, particularly for thicker plates. At the time the US did not have the same shipbuilding trade as the UK. However, Mr Jeremiah Head a past president of the IMechE who had recently toured US works noted that in the US plates were subject to Bureau Veritas tests, equivalent to Lloyds, and he had seen plates 10 feet wide rolled on a three-high mills and had seen a 4,000 ton cargo ship building at Cleveland, on Lake Erie, with plates in her hull up to an inch thick.

3-High Fritz Mill

A problem with rolling mills is that the high rolling loads tend to bend the rolls and this produces a plate which is thicher in the middle than at the sides. Profiling the rolls in a slight barrel shape provided some compensation, but another solution is to provide further larger diameter 'back-up' rolls of a that provide a higher resistance to bending. The first solution was a 3-high mill. The plate could be passed between the smaller diameter driven middle roll and the bottom larger roll in one direction and between the middle roll and the larger top roll in the other direction.

The 3-High Mill is usually thought to have been first invented by John Fritz in 1857, when he was Engineer Manager to the Cambria Iron Company in the United States. However, there are accounts, written at the time, of 3-High mills in use in Staffordshire in 1815, and the first modern three high mill recorded is in a patent to R Roden at Abersychen iron Works in 1853.

The first mill built by Fritz was a rail mill, and its inception, as detailed in his autobiography by "Uncle Fritz" as he became known, is worth quoting to show how an idea has to be fought for in the face of ignorance and prejudice. The original two-high mill had proved to be a failure for several reasons, and Uncle Fritz goes on to say:

" To continue to run the mill as it was, I could see nothing ahead but a most disastrous failure. Having previously given the whole subject my most thoughtful consideration, even to its most minute detail, I was prepared to submit my plans and recommendations to the new Company. My proposal was to build a new train of rolls three-high and twenty inches in diameter. This involved a new engine that would run with safety one hundred revolutions per minute, and it practically meant an entirely new mill. To this proposition they demurred, saying that it could not be done as the expense was too great; besides, the mill they had was entirely new and was supposed to be the best mill in the country, and they were at a loss to see why good rails could not be made on it.

After some time and a great amount of earnest talk, I succeeded in convincing some of the representative shareholders that it was absolutely necessary to make some changes and improvements, and that, if my suggestions were adopted, success was sure.

At the next meeting the subject was taken up with a full Board, and, as I was informed afterwards, the matter was fully discussed, and it was decided to build an eighteen inch two-high train, geared, to replace the train we had, and I was ordered to go ahead at once with it. This was to me a very severe set-back, as I supposed I had Mr. Townsend converted to the three-high direct-action mill. To this order I replied most emphatically that I would not build the geared mill, as it would be money thrown away and time lost. In reply to my refusal to build the mill as ordered, they said my position was high-handed and most arbitrary, and one I had no right to assume, as I was in their employ on a salary for the purpose of managing their works and had no right to dictate to them what they should do. I, in a measure, assented to this, at the same time telling them that if they persisted in running their works on the lines they had laid down for me, there would be a humiliating funeral, and I did not want to remain to attend it, especially as one of the mourners. In a few days after receiving my reply, they gave me permission to build the mill as I wanted it, but suggested that I make the roll eighteen inches instead of twenty. I consented as a compromise - a great mistake - and commenced at once to build the mill, and make other important improvements.

How the Shareholders Protested.

About the time the patterns for the new train and also for the engine were completed, a protest was received at the works in the form of a legal document from the minority partners, notifying the Managing Directors that they would hold them personally responsible for the building of the new Mill. This was a most unexpected set-back, and all the work on the new mill was suspended for a time, and the Directors made another effort to get me to change my plans and build the old two-high geared mill, which the Company had previously, so earnestly urged me to do. I told them I was tired out trying to make rails on the old mill. They suggested that I could make a better mill two-high that would give less trouble, and consequently do more work. I admitted that it could be done, but the advantage to be gained would not warrant the expenditure, and the only thing that could possibly be done to make the enterprise a success was to build the three-high mill.

The next Sunday morning Mr Townsend came to the mill, where he found me in the midst of the regular Sunday repairs. After I was pretty well through with them he took me aside and showed me the protest. My hands being greasy, I asked him to read it to me, which he did. After all these years have passed there is no person other than myself who can fully appreciate the trying position the Managers were placed in. On the one hand I was urging them to build a mill, on an untried plan, as a strong minority called it, this minority also legally notifying the managers that they would hold them personally responsible for the result. On the other hand, I was absolutely refusing to build the mill they wanted; and, besides all this, they ridiculed the idea of adopting a new and untried method that was against all practice in this and the old country, from which at that time we obtained our most experienced Iron-workers. Moreover, the prominent Iron-makers in all parts of the country had said to Mr Morrell that the whole thing was a wild experiment and was sure to end in failure, and that young, determined, crack-brained Fritz would ruin him.

The Heaters and Rollers all opposed the three-high mill, and appointed a Committee to see the Managers and to say to them that the three-high mill would never work, and that they themselves would suffer by reason of its adoption; but if the Managers would put up a two-high geared train, which they said was the proper thing to do, the mill would go all right.

As I now look back to that eventful Sunday, morning, many long years ago, sitting on a pile of discarded rails, with evidence of failure on every side, Mr. Townsend and myself quietly and seriously talking over the history of the past, the difficulties of the present, and the uncertainties of the future, I cannot but feel in view of what since has come to pass that it was not only a critical epoch in the history of the Cambria Company, but that as well the future well-being of my life was in the balance. For, as Mr. Townsend was about to leave, after a full discussion of the Cambria Iron Company's conditions at that time, he turned to me and said, 'Fritz, go ahead and build the mill as you want it.' I asked, 'Do you say that officially ? ' to which he replied, ' I will make it official,' and he did so; and here I wish to say that to no other person so deservedly belongs the credit, not only of the introduction of the three-high roll train, but also of the wonderful prosperity that came to the Cambria Company, as it does to Mr. Edward Y. Townsend, then its Vice-President.

"A Grand Old Smash Up."

Notwithstanding, I now had the consent of the Company to go on with my plan for the new mill, many of my warmest friends, some of whom were practical ironmen, came to me and urged me not to try such an experiment. They said I had taken a wrong position in refusing to build the kind of mill the Company wanted. 'By so doing,' they said, 'you have assumed the entire responsibility, and in all probability the mill you are going to build will prove a failure, and being a young man your reputation will be ruined for life.' To this I replied that probably they were right, but that I had given the subject the most careful consideration and was willing to take my chances.

The work was now pushed on as fast as possible. In the construction of the mill train I made a radical departure from the old practice, which was to place breaking pieces at dangerous points in the train: these pieces were expected to give way under certain strains so as to save the roll from breaking. One of the previous methods was to make the coupling boxes and spindles light so that they would break when any extra strain came on them; and the leading spindle had a groove cut round it to weaken it, so that it would be sure to break before the rolls, The result was the constant breaking of some of these safety devices. In addition to all these devices, there was what was called a special breaking box on top of the rolls which held the rolls in place. This was made hollow so as to crush if the strain on the rolls became too great. I directed the Patternmaker to make this box solid. The Mill Manager, seeing the pattern was solid, went to the Patternmaker to have it changed and made hollow, as he supposed it had been made solid through a mistake. The Patternmaker refused to alter the pattern, saying the old man (as they called me over fifty years ago) had ordered it to be made that way. 'Well,' said the Manager, the old man has gone crazy; and if the box is put in as it is, the mill will be smashed to pieces, and I am going to see him about it.' This he did, and I told him the box was going in solid, as I would rather have a grand smash-up once in a while than he constantly annoyed by the breaking of leading spindles, couplings, and breaking boxes; to which he replied, ' By God, you'll get it ! '

When it became known that I had abandoned all safety devices, another violent storm arose, and it was of such a character as to much annoy Mr. Morrell. He was a very clever gentleman, without experience in the manufacturing end of the business, and, being known as the General Manager of the plant, he was naturally worried. This, of course, gave me much trouble to keep him in line, as every person he would meet that knew anything about the business would tell him of the great failure that was in store for the Cumbria Iron Works. Some one told Mr. Wood, the President of the Company, all about what was going to take place when the mill was started. I was afterwards told that he listened attentively to what they had to say and then said to them: Mr. Fritz has done many clever things for us that were said would never work, but always did and I shall not interfere with him or his plans.' . . . "

How the Mill was "Tried Out"

The train was now practically completed, with all breaking devices abandoned. The old mill was stopped on the evening of the 3rd July, 1857, and after the 4th I commenced to tear the old mill out and get ready to put the new one in, and also to put the new engine in place at the same time.

Everything in the Mill Department was remodelled and the floor line raised two feet. On the 29th of the same month everything was completed and the mill was ready to start. I need not tell you that it was an extremely anxious time for me: nor need I add that no engraved invitation cards were sent out, that not being the custom in the early days of Iron making: had it been, it would not have been observed on that occasion.

As the Heaters to a man were opposed to the new kind of mill, we did not want them about at the start. We secured one, however, out of the lot, who was the most reasonable one amongst them, to heat the piles for us. We had kept the furnace smoking for several days as a blind. At last, everything being ready we charged six piles, At about ten o'clock in the morning the first pile was drawn, and it went through the rolls without the least hitch of any kind, making a perfect rail.

You can judge what my feelings were as I looked upon that perfect and first rail ever made on a three-high Mill; and you may know in part how grateful I felt to the few faithful and anxious men who stood by me during all my trials and difficulties among whom were Alexander Hamilton, the Superintendent of the Mill, Thomas Lapsley, who had charge of the Rail Department, William Canam, and my brother, George.

We next proceeded to roll the other five piles. When two more perfect rails were rolled we were obliged to stop the engine, as the men were all so intently watching the rolls that the engine had been neglected, and, being new, the eccentric had heated and bent the eccentric rod so that the engine could no longer be worked. As it would have taken some time to straighten the rod and reset the valves, the remaining piles were drawn out of the furnace on to the mill floor.

"About this time the Heaters, hearing the exhaust of the engine, came into the mill in a body, and from the opposite end to where the rails were. Seeing the unrolled piles lying on the mill floor, they took it for granted that the new train was a failure and their remarks about it were far from being ill the least complimentary. Mr. Hamilton, coming along that time and hearing what they were saying about the mill, turned around, and in language more forcible than polite told the Heaters, who were Welsh, that if they would go to the other end of the mill they would see three handsomer rails than had ever been made in Wales, where the greater part of the rails used in this country at that time came from, as well as the Heaters who were so bitterly opposed to the three-high mill.

The above is a first-hand account from the inventor himself of how the Three-High Mill came to have a place in the sun. Uncle Fritz's trouble did not end there. The mill started on a Thursday and worked the whole of Friday, day and night shifts, on to noon on Saturday, when work was stopped for the week. On Saturday night the mill building, which was of wood, was set fire to by some incendiaries and burned to the ground. The mill was, however, re-started within 30 days of the fire, but without a roof ; and the new buildings, which were of brick, were finished and roofed over with the mill running full time during the progress of the work.

Three-High Lauth Mill

In the type of mill invented by Fritz the middle roll was fixed, and the top and bottom rolls were adjustable. This was quite practicable for Section Mills when the rolls did not require to be adjusted between every pass. For Plate Mill work, however, this type of Mill was superseded by the one invented and patented by Mr. Bernard L. Lauth of Pittsburg, U.S.A.

In the Lauth mill the bottom roll was fixed; the middle roll, which was smaller than the top and bottom rolls, being raised and lowered by a power operated lever alternately as the piece passed under or over it, The top roll was adjusted by screw gear to give the draft in the usual was. The small middle roll was not subject to bending stress, as it was always in contact with one or other of the large rolls.
Mr Lauth read a paper at the Glasgow meeting of the Iron and Steel Institute in 1872, in which he described his mill as follows:

"In the United States there are about 23 mills running three-high, and the character of these mills is as follows. The hard rolls are of the usual size, but between them there is a roll of smaller diameter: thus for a 4 feet roll by 20 inches diameter, the small roll would be 13 inches diameter and for a roll 6 feet long by 22 inches diameter, the middle roll would be 16 inches diameter. The rolls are all turned perfectly straight and level, so that they bear all over, and a stream of water is constantly kept on each roll to keep it perfectly cool.

The effect is that there is no expansion and contraction of the rolls, and the sheet or plate is rolled to a perfect level free from all buckling. The surface of the sheet or plate is very smooth, the water having the effect of washing off all the scale and preventing it sticking to the rolls. Some people are under the impression that by using so much water the sheets and plates would get cold. Such, however is not the case, as the water runs off in globular form, and in practice it is no impediment. By the old system of rolling, the Plates and Sheets are usually thinker in the middle than at the edges. By this system they are rolled all over to a uniform gauge, in consequence of the rolls being kept cold.

The reducing power of the middle roll is very marked and this is accounted for by reason of the smaller area which is covered by the grip of the plate, in consequence of the diameter of the roll being smaller. The effect is, that a larger draft can be put upon the plate or sheet than by the old system with the same power involved in the machinery."

The Clydebridge 3-High Plate Mill, that operated between 1922 and 1960, was a fine example of a Lauth mill. It was made by Davy Brothers Ltd, Sheffield. The top and bottom rolls were 36 inch diameter, whilst the middle roll was 24 inch diameter. The length of all rolls was 9 feet on the barrel. The roll necks for the top and bottom were 26 inch and those for the middle roll were 16 inch diameter, the lengths being 24 inches. The pinions were machine cut double helical teeth 56 inches wide on the face. The housing screws were 12 inches diameter and operated by a DC motor of 100 HP. The lifting tables on each side of the mill had seventeen 17 inch diameter rollers, each 7 ft 3 ins long, with journals 5 ins x 10 ins. Each table was provided with two 60 HP DC motors. The lifting rig was operated by a DC motor of 100 HP. The mill was driven by a double armature motor of 13,000 HP at 65 RPM. The motor gave constant torque from 0 to 65 RPM, and constant HP from 65 to 110 RPM.

Four-High Mill

The 3-High Mill has been superseded for plates and strip by the 4-High Mill, where the piece passes between two driven work rolls, each supported by larger, un-driven, back-up roll, one above and one below the work rolls. This allows the power to be transferred through the smaller work rolls and ensures that these remain horizontal and parallel, despite the rolling loads, through the support from the larger back-up rolls. The Clydebridge 4-High Plate Mill (1962) work rolls were 39 inch diameter by 132 inches wide at the barrell, and the back-up rolls were 60 inch diameter. Similar mills were installed at Consett (closed in 1980) and at Rautaruukki in Finland (modernised and still operating) and the mill shared parts, such as the 27 ton drive spindles, with the Ravenscraig Roughing Mill. The newer Dalzell heavy plate mill has 72 inch diameter back-up rolls (each about 74 tons), which are so large that special railway carriages had to be constructed for their transport to the Works.

Shears

An early plate mill would have a steam or water powered shear and the plate would be manipulated round to be shorn at the ends, or sides, or for splitting. In early shears, and with light plates, the plate would be manipulated by hand, with a trestle, called "the horse" being used to support the plate when being cut. As plates got heavier upturned castors were introduced, first in America, to support the plates. Later mechanical tables were developed, such as the Ennis table, (designed by Mr Ennis of Dorman Long & Co) used at the side shears in Clydebridge in the 1920s. This was a moveable roller table, the whole of which could be moved past the shear; and the table included electro magnets for adjusting the plates in front of the shears. These were all replaced with continuous roller tables, magnet manipulators and hydraulic clamps when the side cut shears were upgraded and new end cut shears installed in the early 1960s. Despite this the side cut shears were often still referred to as the Castor Shears.

For thinner plates a Schloemann Rotary Shear was installed at Clydebridge in the 1960s. This sheared both sides of a plate continuously with 2 circular blades at either side of the plate (rather like the operation of a rotary tin opener). The strips cut from the side fed through rotary chopper heads, which were 2 contra rotating drums with helical cutting blades. Other heavier shears installed at this time for cutting the ends of plates were electrically driven through reduction gearing located on top of the shear.

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