Friday, October 10, 2014

Return to Hals / Icelandic Furnace

From Fall 2007 through Fall 2008, plus one in Spring 2012, DARC mounted a series of five iron smelts specifically aimed at re-creating Viking Age furnaces from Iceland. The archaeology was based on excavations by long time friend (and unofficial adviser) Kevin Smith at the Hals site. This was a long term, 'industrial' scale iron production operation, with the remains of a number of bloomery iron furnaces uncovered.

As a refresher, the Icelandic system is basically a cone made of piled up grass sod, with a cylindrical hole in the centre (the furnace). At Hals, these were constructed entirely above ground level. The cone was then boxed with timbers. The space between the timber and cone was then filled with earth to create a working surface at the top level of the cone / furnace mouth.
Possible Furnace Construction - based on Hals
More details on the site, and the logic behind our reconstructions, can be found in the semi formal description 'Towards an Icelandic Smelt'

An important difference from other furnace builds we have undertaken is that there is no true clay found on Iceland (our normal construction material!) My suspicion is that at Hals, the sod itself forms enough barrier to contain working gasses and heat of the furnace. The timber and earth fill is merely to create the elevated working area for charcoal and ore workers.
I have yet to calculate the required timber or earth needed for the full above ground build. Obviously there would be a considerable volume of both grass sod and earth required. The timber would have to be purchased, most likely in the form of wooden fence posts.


Remains of the Fall 2008 Furnace
Over the earlier series, the working furnace was set back into the low earth bank on one side of the smelting area here at Wareham. (This done to conserve on the materials required for a full build, especially as individual 'problems' were investigated.)



Intended construction - Icelandic Furnace
What I am considering is to simply use the existing earthen bank to contain the lower part (roughly half the needed height) of this construction. This will limit the amount of dirt needed to be dug and shifted. Also greatly reduce the amount of timber required for the upper box construction.
The lower part of the furnace face will be constructed of stone - in effect creating a 'slag room' style, similar in this aspect to what was used for the Turf to Tools project.

The result here is that Sunday October 12 will be a * working * day at Wareham. Sod will be cut and stacked (from a piece of yard that is intended for a garden). The old furnace will be cleared and some earth dug away. Ideally at least the base structure will be laid for the new furnace.
Other hands extremely welcome!

The full build will all be (hopefully) completed in time for a full run of the Hals system (smelt) on Saturday November 1.

Tuesday, September 30, 2014

Custom Knife ?


Readers:
I have most certainly gone over these details here in the past - as well as covering these points at various spots on the web site:



On 30/09/14 4:04 AM, Peter wrote:

I am looking for a knife for a while now and have not yet found one which met my requirements for a price I’m willing to pay.
"Layered Drop Point" - 1997 : This is the blade Peter referenced. It has a 3 1/2 inch long blade and a specifically shortened handle and one piece construction
A true statement is always 'you get what you pay for'
This cuts both ways - as you *should* expect higher quality at a higher price.
I need a knife which will cut my fire wood as well chops 1 tot 2 inch branches which wont turn blunt in 2 days. I only need 4 inch length of blade.
These three requirements may work against each other.
At 4 inches, the blade would have to be considerably thick to create the kind of impact you would need for this kind of heavy hacking task. This not necessarily a problem, as a blade with 5mm or more in thickness along the back, and a relatively wide blade can certainly be forged.
A larger concern is balancing your requirement for edge holding against the requirement for excessive durability.
The problem is that a harder metal is required to produce a cutting edge that retains sharpness. However, harder metal is also more brittle - more prone to breaking if subjected to extreme use. (Consider a scalpel or box cutter blade  = extremely sharp, holds that edge, but also extremely fragile.)
Generally 'heavy hacking blades' are created from a middle carbon steel, to balance edge holding with shock resistance.
One solution is to create a sandwich with a high carbon core (edge holding) layered between two pieces of mild steel (shock resistant).

Be aware that a blade formed of * just * layered steel will  * not * have the edge holding ability of a plain high carbon one.
Because the layered block alternates hard and softer metal, the cutting edge created will actually alternate (in fine detail) between areas of hard and soft. This in fact creates a cutting edge that will wear unevenly.
The true value of layered steel is not in its edge holding - but in greatly increasing shock resistance. This effect most functional in very large blades (read sword sized).

My current method of creating layered steel blades (cross section)

XXX
XXX
XXX
FVF
FVF
V

X = layered and twisted
F = flat stack layered
V = high carbon slab

You can see that in effect, the back area of the blade is composed of the more flexible (and highly decorative) twisted 'pattern welded' material.
The blade area is composed of a slab of hard carbon steel, protected by two blocks of layered material
On sharpening, the hard carbon steel is exposed to form the actual cutting edge.
"Pattern Welded Sgian Dubh" - 2006 : This blade is constructed in the method described above.
An alternate solution to these functional requirements would be to use some exotic alloy steel. I personally do * not * work with those kind of materials. Most require specialized forming and most especially heat treating steps or equipment that I just to not have access too. (This is the approach used by most 'commercial' knife producers, with ground blades from stock bars, which are then industrially heat treated.)

  I like to know how much it costs to make a Layered drop point knife of layered steel, could you give me a estimation of the costs?
Specific quote will be determined by the exact details of a specific design.
Typically, it will take me three working days to forge up the starting billet of layered material as described - enough to then forge out two knives (depending on blade size). The process of forging, then grinding and polishing a single knife takes another two and a half days.
Hilting adds both more time and materials costs, so needs to be quoted separately.

The current rough estimates (blade only) is posted on the web site :
Flat stack 'Damascus' = $200 / 4 inches plus $40 per inch larger
Twisted core 'Pattern Weld' = $250 / 4 inches plus $50 per inch larger
http://www.warehamforge.ca/knife.html

Note that for the one piece knives seen on the web site - the price is calculated for the * entire * length (blade plus handle)
(You might notice that this is a stupid small amount - considering the amount of time expended on each knife - in a seven day 'shop week' I can basically only produce TWO blades.)
And the final question do I understand correctly that you charge in Canadian dollars?
Yes - prices quoted in CDN funds.
If paying in alternate currency, there will be a conversion fee added (cover bank losses)
50 % deposit required on order 'non refundable against work undertaken'
balance due in full before shipping
Shipping costs added on top as required your destination
(HST added within Canada)
Any Customs Duties remain customers responsibility
Production time dependant on current commissions


  One of the continuing problems any artisan maker has is sorting the serious from the casual. 
I do normally treat every initial request as if it was serious and going to lead to an actual commission. In actual fact at best only one in ten leads to actual paid work.

Friday, September 26, 2014

Pattern Weld Sword (continues...)


 Thursday I ground down the welded billet to remove the lumps and gaps. 
These come from the edges of the individual rods, which have been forged down to * roughly * square from either round (spring steel edges) or octagon (central layered and twisted). Imagine what would happen if you compressed a pile of O shapes:

OOOO

You can see that this would result in a set of small v shapes between each of the rods. 
My own experience is that these can vary a lot in size, depending on the actual shape of the individual rods, success of the welding (skill of the smith?). Sometimes these gaps will collapse in and weld up correctly in later forging steps, but I have found it better just to grind down to solid metal before proceeding to actually forging the blade shape.

What might prove of interest here is the effective * loss * of material.
Starting rough forged billet (after welding) = 3.2 kg
As ground to remove gaps = 2.8 kg
Loss = .5 kg

Next : Forging the blade itself

Thursday, September 25, 2014

a Pattern Welded Sword...

Since my return to Wareham, I have been working seriously on a (slightly) postponed commission : A Norse type pattern welded sword *

The two starting blocks were composed of a total of 13 individual plates :

M-I-M-L-H-L-M-L-H-L-M-I-M

M = MILD STEEL, inner at 1/8", outer at 3/16"
I = WROUGHT IRON, 1/4"
L = L-6 (nickel mid carbon alloy), 1/16"
H = 1095, 1/8"
All pieces at 1" wide x 6" long

After welding to blocks, each was drawn to a rod roughly 70 cm long x 12 cm.
Next each was facetted to octagon, then given three sets of twists (alternating with straight sections).
The two  cores were forged square, and fitted to two pieces of 1045 (coil spring) and prepared for the next stage.

Rods wired, prepared for welding
Showing starting length
Detail of tip construction


At start of welding, the bundled rods were roughly 80 cm long X 5 cm wide X 12 cm thick.
There are two possible ways to fit the mid carbon steel cutting edges, a one piece wrap or two separate pieces. Both present their own forging problems, in the past I have chosen the two piece method. (The challenge here is welding tight the small triangle where the four pieces interlock.)

The welding process took me 3 1/2 hours, something like 16 (or more?) individual welding heats. The first cycle over overlapping 'travelling welds' were all done by hand. This was followed by a second series of heavy compaction welds using the air hammer.

After welding, note length and width change
Detail - The tip after welding
The finished billet produces roughly 95 cm of solid material (it is expected to cut at least 5 cm from the tip end).  At this point the billet is roughly 4 cm wide and 12 cm thick. It currently has a weight of 3.2 kg.

The next step will be to grind the surface down, removing surface flaws in the welds. These are primarily caused by the slightly rounded edges of the individual cores and edges. Some of the excess weight will be lost at this step.

In the creation of the final sword, this represents close to 2/3 of the actual work - and most certainly the majority of the difficulty.


* There is a lot of confusion on language here.
I use 'pattern weld' the way I first learned the term - as the archaeological definition :
Two or more layered rods, twisted, which form the core of the blade.
The starting stacks combine separate low and higher carbon plates, usually as low layer count.
The twists will alternate and match with clockwise and counter-clockwise direction, often including straight sections.
Most commonly a separate mid to high carbon rod is welded to each side of the cores to form the actual cutting edge.
The method was used primarily in Saxon and Norse blades, known samples ranging roughly from about 400 - 1000 AD. The ultimate example is the complex blade from the Sutton Hoo burial (a royal status object, consisting of eight individual cores, mirrored in pairs side to side and top to bottom. It was most likely created in modern day north Germany or south Denmark, about 600 - 625 AD.)

The Sutton Hoo Sword (in the British Museum)
 from : http://dailymythogies.files.wordpress.com/2011/03/p10102341.jpg

Replica created by Scott Langton
from : http://i292.photobucket.com/albums/mm36/cerishields/SuttonHoosword-resized4.jpg

 

February 15 - May 15, 2012 : Supported by a Crafts Projects - Creation and Development Grant

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