Hearth Steel

There has been a lot of discussion on the forums about using small hearths to melt low carbon iron and steel and carburise (adding of carbon) it to produce a hardenable carbon steel.

After discussing some ideas with my friend, Dan Prendergast, we decided to have some experiments trying to produce some of these “raw” steels, at his workshop- Didbrook Forge in Gloucestershire.

http://www.didbrookforge.co.uk/

Whilst the produce of one of these small furnaces appears very much like a true “bloom” from a bloomery furnace, the method is dissimilar because in a melting hearth, you do not start with ore and thus the whole process is much simpler.

 

Didbrook forge is a historic forge in the heart of Gloucestershire, which has worked continuously as a forge for over a century with parts of the house dating to the  17^th century and beyond. It was a true pleasure sharing the workspace with Dan for a few days and being in an old workshop again, for me, was very reminiscent of my father’s old forge, “The Wharf” which we left some 7 or 8 years ago and has now subsequently been demolished.  I grew up knowing the old workshop and I have always felt comfortable in such spaces.

 

 

 

I first met Dan when working at Hampton Court Palace in London and discovered we had shared interests in Bladesmithing, Ironwork, history and tradition. We had crossed paths before without meeting as I had callously bought a powerhammer that Dan had been keenly watching for while…

But back to our melting.

We had three attempts, each time altering the furnace a little but each time using similar ingredients of mild steel bar and a small quantity of cast iron, perhaps ten percent on each melt, which we believed would likely add bursts of high carbon to the mix.

 

For fuel, were supplied with some locally produced charcoal from old coppice woodland, this charcoal was very good and clean to work with, chopping well with a pleasant clink.  Charcoal I have used previously had left me so filthy with the soot that I was hesitant to handle the stuff too much, but this batch barely left a mark on the skin when handled.

 

It was either Mark Green or Dan O’Connor  that I read had done a great deal of research into the variability of charcoal and I remember that one of the traits of good forge/furnace fuel was this cleanliness.

The ‘Coal was roughly split and chopped and half-heartedly sieved to separate the very fine finings and powder from the proper sized pieces before the hearths were lit.

The first “furnace” was built quickly with house bricks and a rich natural clay from Dan’s garden, using the water cooled tuyere from one of the forges. The furnace was approx. 10 inches square, which with hindsight was certainly much too large as we used much more charcoal than we needed to- That said, it did work.

 

 

We were both surprised to find a “bloom” in the basin, swaddled with ceramic slag, weighing about 1200g. This first bloom was allowed to cool before we cut it up to investigate and process it. We found it to be a high carbon material so we decided to forge the pieces into strips, weld and fold and weld again until we felt it was suitably consistent.

 

 

 

These processes were undertaken with striking sledge and hand hammer as Dan’s very beautiful, 19^th century, French made power hammer is not quite up and running yet, so it was porridge power all the way.

 

 

 We then divided the material and each forged a knife.  

 

Dan had in his collection an excellent little book called “Knives and Scabbards” which featured artefacts taken from excavations in London dating to the medieval period.  One blade form took my fancy and I decided to produce a blade in that style as I felt the Hearth steel’s material aesthetic qualities would suit it well.

The hearth steel was forge welded in coke onto a wrought iron back and tang to maximise the size of the blade, but also to best display the limited amount of the decorative steel we had available.   

The knives were both quenched in warm water and took great hardness and did not crack. Dan proceeded to polish his knife and etched it, revealing the wonderful character but also a distinct hardening line. My knife has not progressed this far but I am optimistic for the vibrancy that will be displayed in the steel once it is finished. The knife I am copying had a small brass bolster which I will replicate. The knife will have horn or antler scales, fitted with hand-made brass or copper tubular rivets. I will of course share its progress here when I get round to it. We were both surprised and pleased at how well the metal performed and we decided to proceed with a second burn.

 

This time we forwent the brick furnace, instead opting for an all clay and straw structure with a much reduced diameter and thus improved fuel consumption.

 

The second burn was excellent, taking under an hour before we decided the tuyere had become obstructed with the bloom and we stopped feeding it.

This time we forged the bloom right away after breaking the furnace open. Working the bloom quickly with striking sledge and hand hammer- despite being hot, the bloom was noticeably tough and resisted our force, yet it displayed no “red-short” brittleness and held together very well with little to no pieces coming off.

 

Once we began squaring the stock it became clear that there was a large split running neatly through the piece, dividing it nearly in half. We decided to separate these two halves and proceeded to work them separately as Dan’s forge has two large coke hearths.

I was struck with how solid the steel felt under the hammer and we were both able to forge the material into barstock without folding the bloom at all.

 

Spark testing again suggested some good high carbon content

Dan did a quick polish and etch and it showed a lot of clear activity.

 

These pieces were divided equally into seven parts before being dispersed as much as possible in a stack to ensure optimum carbon distribution, these were welded and folded an number of times and left as stock for Dan to approach at a later time.

The third furnaces followed more closely to the second burn, only with more stout walls to help prevent collapse. The hearth bloom we extracted from this furnace weighed 1400g and sparks with good carbon on each of the points tested.

 

I took this raw bloom home to be forged at a later date as I have a power hammer to help with the processing.

This last burn took just over two hours from digging the earth out of the yard, mixing the clay, building a furnace, lighting and doing a burn and extracting the piece. I think we were both impressed at the speed of the turnaround.

This was a fun experiment that produced some great steel, I’m sure we’ll do it again, perhaps with a smelt as well….

Thanks Dan, Vivian, Peanut and Betsy, it was a real pleasure.

Grosse Messer

 

Some time ago I was contacted by a customer to produce for him a blunt, re-enactment sword in the style of a German “Grosse Messer”, meaning literally “big knife”.

These weapons of the renaissance form an intriguing family that take a variety of form and sizes, the style we elected for is of the longest type, a “krieges Messer”, a “war knife", identifying it as a type exclusively intended for use by the professional soldier of the day.  What's unusual about that is that many of the Messers were not exclusively for fighting; many occupied that intriguing place in the contemporary society as tools, status symbols, civilian personal defence and hunting swords. They existed as rudimentary Civilian implements and objects of the elite.

Their name “big knife” does not simply infer that they were large single edge blades, but reveals something of their manufacture as they were made by knife cutlers (a guild distinct from the sword cutlers) and also exploited a legal loop hole of the time that a peasant could not own a sword, yet there were no limits to what defined a knife, so knives became larger.

The design of this hand forged re-enactment sword was based on several modern examples including the fine piece by Peter Johnsson, as well as my own research on original pieces. The blade was forged from En9 carbon steel.

This is the story of the sword’s manufacture.

 

The starting stock for the blade was 20 inches of 40x10 En9

 

 This was forged out to 44 inches before a clip was forged in and the bevels were established, which produced the natural curve.

 

 

 

Once the outline of the sword had been formed with the bevels roughed forged, the spare material  in the tang end, was cut off to be forged into a punch to cut the hole in the guard.

The design called for a double fuller to be forged in so a tool was made to this, forging from both sides of the blade simultaneously.

 

 

 

Once these were forged, it was time to begin hand polishing  the blade with files and abrasives, the fullers were polished by wrapping 8mm diameter steel rods in abrasive and rubbing in slow even movements to ensure that the fullers terminates gracefully.

 

 

 

Once a rough polish had been achieved it was time to move on to the hilt parts, these were all hand forged from mild steel using a range of techniques.

The starting stock was a piece of 20mm square

 

This was knocked down to something like 16x 25.

 

The offcut from the tang was forged into a punch the same width as the widest point on the tang (pommel end) and used to hot punch out the slot.

 

 

 

Once the slot had been cut, the billet was marked out and the sections that would become the quillions were separated using a top set forged some time ago.  Care was taken not to intrude in to the newly punched slot, which would have damaged or distorted it.

 

 

 

The blanks for the quillions were then drawn out under the Goliath power hammer.

 

The Nagel hand guard was forged carefully from one piece.

 

A large rasp was used to set the shoulder before, finally, a bolster was employ to upset the back and fully square the shoulder. The long rivet or mortise would be trimmed shorter before final assembly of the guard.

 

 

 

 

After the clamour of forgework comes the inevitable fettling and making of dust, quite course dust at this point, but dust all the same.

The cross piece and the nagel were shaped and formed with files and abrasives until they were In a condition to marry.

 

These were fitted to the sword and progress could begin on fitting the oak grip and the asymmetric pommel.

 

Once all the holes had been drilled and the timber fitted, everything was secured.

 

 

Like in the originals, copper shims were carefully fabricated do ensure absolute tightness.

 

Copper tubes with steel rods were used as rivets- this exactly replicates the method used on originals.

The nagel guard was peened into a counter sunk hole on the reverse, piercing the blade securely in position.  Once the mortise had been peened it was nearly invisible.

The timber was sealed with several protective coats of linseed oil, which encourages any interesting aspects of the grain tremendously.

This also prevents filth from the hands marking the wood and the tannins from the oak staining the skin. The contrast between wood, copper and steel was also increased and the object is left with a satisfying variety of textures and colours.

Two astrological symbols were carved into the grip upon the customer’s request and the piece was finished.

Thank you.