Monday, 15 July 2013

Sunday 14th July Wimpole Hall blacksmith’s shop.

I bumped into Magnus (picture below) at the Scything competition a few weeks ago and arranged to meet up for a lesson in the use of charcoal and axe forging. Magnus is a weapons historian and makes blades using very old tried and tested technology.

This old forge at Wimpole Hall is a masterpiece of design. Stable area for horses on the right. Forge area with small window in the middle.Bellow at the back.  Fuel access hatch on left - charcoal is only kept in small quantities in the forge are as it is highly combustible.

 I have been attending an adult blacksmiths run by the London Borough of Newham for some time (three years +). I have been brought up on coke, which in historical terms is a very new fuel source. I believe the first steel officially recorded was made by Bessemer in 1850. So I think we can all grasp the fact that blacksmiths controlled the migration of carbon (from charcoal) into their iron and have been making some very nice weapons for at least 2,500 years.

So here is my axe halfway through forging, the top end is the poll (back of the axe) the metal has been compressed to make it thicker than the rest. The left hand has been forged to an angle. The next step is to rearrange the fire (make it very much bigger) to obtain welding temperature. The inside was ground to clean the soon to be fire welded surfaces.  

So once it got to welding temperature it was given some borax, returned to the fire, reheated until the surfaces were fluid and then pushed together – hit it too hard and all the molten surfaces are pushed out of the weld. Then the rest is just forged using normal methods. It was hardened and tempered using 50/50 Neats-foot (cattle) oil and linseed.

So here is my first wrapped axe. It had just been heat treated, note the hot charcoal still in the handle space. The cutting edge is touching the anvil which is acting as a heat sink. 

What I failed to mention was that during this process we allowed the axe to rest in a carbon rich oxygen depleted environment a few times, which allowed the steel to acquire carbon on the cutting edge.

This is buy far the most important bit. Sitting on top of heat packed in charcoal with no air blast = carbon acquisition. Sitting in front of air blast = carbon depletion. The trick is to make sure the cutting edges do not receive hard air blast but do get an opportunity to soak in a carbon rich environment.

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