Saturday, July 19, 2014

a bit about HAMMERS

(edited from an e-mail)

Although you can make due with almost anything, precision requires control, and hammers are pretty individual. This is primarily due to the dynamics of the human body. Those who have seen me know I am tall, thin and relatively light framed (5 ft 11 / 155 lbs). This usually means a more balanced head shape, and a longer, typically thinner handle.

The weights are also important. For most lighter weight forging, a 800 gm (1 1/2 lb) is going to be most useful (and desirable). For the heavier work (really much over 1/2 square bar) a 1000 gm (2  lb) is going be required.
I personally find a 1.5 kg (2 lb) a bit heavy, although if the design is good, can manage it with care.
' Impact energy of a stroke is mass times velocity '. Leaving mass penetration aside, with my lighter frame, I tend to use a lighter hammer moving faster, with more stokes and the ability for better control. (I have seen over the years, too many people, especially the hobby smith, will use much too heavy a hammer. Then complain that their elbow hurts! ' It don't matter how hard you can hit - if you miss! ' )



Typically, any smith will have one hammer which is their primary. Then a couple more they use for more specialized forming. And then a pile of hammers they virtually NEVER use. 
A useful piece of advise : Don't rush out and buy an expensive hammer just as you start. Best is to try a number of different profiles, to find one that best suits you personally., * Then * spend the money for what will likely become your primary forging hammer. (A good quality hammer can easily run $75 +) There is no significant reason not to just purchase 'cheaper' hammers - for those you only rarely use anyway.


Check and see if you have any local sources for 'cheap' hammers. Surplus stores and 'low end tool' places can often be a good source.  We can get some square faced cross peens in Ontario that come in from China. While I am * not * in favour of Chinese tools in general, these run less than $10 around here and are acceptable quality, especially as 'seldom used' hammers. 'Twin Swallows' is one brand name.



 
'Historic - Square'
These are both Chinese square faces, in the classic cross peen shape
These used to come with very poor quality wooden handles (which you basically want to replace with proper ash handles). Then for a while they came with fibreglass as seen. The fibreglass is not ideal, but actually better than what ever crap wood they once used. Lately, these come with * plastic * handles, which is virtually impossible to use. (Every stroke seems to bounce the return into a different direction - very difficult to control!) Balance that against the cost, $8 here last I bought one.
The heads are made of a basic quality mid carbon steel.
I will buy these, take off the handles *, and re-forge the heads to make other shapes. The second hammer is one such, re-shaped to replicate the shape of hammer found in the Mastermyr tool find (Gotland, Norse, c 1150)




'Round Face'
Here are two 'antique' hammers, one at 1 1/2, the other at 2 lbs. This style was common here for farriers in the early 20th. The weight is fairly central to the handle, and they are reasonably evenly balanced, front to rear. The faces are fairly wide, and typically the peen is quite broad. You do have to keep your eyes open, but around here at least there is a fairly good supply of these. Typical prices are about $20 - $25 each.




'1000'
This is a 1000 gm size (for comparison), with a kind of 'semi octagonal' head shape. The peen is medium to sharp. I find this specific hammer quite balanced and easy to control. I got a number of these, an end of lot from a closing factory here in Eastern Ontario. 





'Favourite'
This is  * my * hammer. I've been told it is a German Engineer's Hammer, produced in the inter war period. I have only ever seen one other one in all my years smithing and travelling. This is an 800 gm, I must do at least 80 % of my forge work with this hammer - and have been using it some 30 plus years at this point. (Surprise is that I got this at a yard sale for all of $8, completely at random - just as I was starting to get serious about blacksmithing.)





* Home Hardware (here in Canada) sells a " 16" Blacksmith's Hammer " handle. Get your local to check their inventory, they likely will have to order them in for you. (And keep a spare in the shop!) Cost is about $7. These are an excellent straight grained ash or hicory. They have the required oval eye (not square like a carpenter's hammer). Do remove the varnish (prevents blisters) and re- shape the handle to thin it out below the head. (Better to break a handle than put extra shock into your elbow!) You can see I wrap some hockey tape around the shaft below the eye - this is to protect the wood if I miss when forging elaborate curves around the far side of the horn. (We all miss * sometimes * !)



Monday, July 14, 2014

Turf to Tools - OUTLINE

This is the draft working schedule for the Turf to Tools project at the Scottish Sculpture Workshop, Lumsden Scotland, in August:
SATURDAY SUNDAY MONDAY TUESDAY WEDENSDAY THURSDAY FRIDAY
9 10 11 12 13 14 15
Available              
AM work site organize furnace build SMELT 1 clear ? CONSOLODATE 1 BLOOM - BAR 1 materials prep
PM smelt tool build materials prep SMELT 1 forge build ? BLOOM - BAR 1 AXE 1 clear ?
Note     furnace test     mild steel axe furnace repairs?
16 17 18 19 20 21 22
Available             Crannog Centre?
AM SMELT 2 CONSOLODATE 2 clear ? AXE 2 spare ? ARISTOTLE build CC lecture ?
PM SMELT 2 BLOOM - BAR 2 BLOOM - BAR 2 AXE 2 spare ? ARISTOTLE fire materials prep
Note ore test     bloomery axe      
23 24 25 26 27 28 29
Available Murray  
AM SMELT 3 CONSOLODATE demo
PM SMELT 3 AXE demo
Note historic ?  
30 31 1 2 3 4 5
Available    
AM ARISTOTLE COURSE ARISTOTLE COURSE
PM ARISTOTLE COURSE ARISTOTLE COURSE
Note    

Friday, July 04, 2014

Pictish Iron : Bloom to Bar

Continuing the commentary related to the 'Turf to Tools' project coming up from August 9 - 24 at the Scottish Sculpture Workshop.

An initial test run of a Pictish Late Iron Age bloomery iron smelting furnace was made in Wareham on June 14 :

Kelly Probyn-Smith holding the freshly extracted bloom mass

The data from the smelt:
Burn rate - average 10 - 11 minutes per 1.9 kg charcoal bucket measure
Total ore added - 31.1 kg (28.3 kg 'dry' weight)
Ore additions range from 1 - 2.5 kg per bucket
Total charcoal used - 61 kg
Total time - 1:15 for preheat / 5:30 main sequence to extraction
Finished bloom weight - 5.2 kg
Yield - 18% (from dry ore weight)

Resulting Bloom - only partially scored

The important next step in having usable iron is compacting the spongy and slag containing bloom down into a dense (and crack free!) working bar for the blacksmith. This is a step often overlooked by the archaeologist, and poorly understood and researched.

The next day, we were joined by David Robertson and one of his students (Mike). The session was to at least start the process of compacting the bloom towards a working bar. Using my hydraulic press, the rough mass was compacted (at welding heat) down to a flat plate about 5 cm thick. This plate was then cut into four roughly pie shaped pieces. At this point a more accurate estimate of carbon content via spark test could be made of the interior. The estimated result was a surprising .60 to .70 carbon - a tool making material.
Both David and Mike worked at compressing their quarter pieces down towards a possible block, to their credit working all hand tools (in a coal forge).

One of the resulting quarter sections

A couple of days later, I took the section seen above and forged it down to at least a first stage 'block'. The piece I started with weighed 1278 gm.
I had the services of my 50 lb Robertson air hammer, plus my 30 ton hydraulic press. All heats via my large coal forge (bottom blast). Hand hammer was a 1000 gm.

The full working cycle (number of heats) :

(compress surfaces on hydraulic press, at welding X 3)
(cut in half, then to quarters on hydraulic press X 2)

Light welding by hand, surfaces and edges X 6
Attempt to work down edges on air hammer (not effective) at welding X 2
Compress on hydraulic press to brick at welding X 3
Work 4 sides to block on air hammer at welding X 2
Weld back both ends by hand X 2
Pull to billet, starting on side surfaces at welding on air hammer X 2
Flux and weld by hand over centre flaws on top and bottom X 2
Draw to even billet on air hammer X 1
Clean up to final shape by hand X 2

Near the start, after edges were welded down by hand

Total heat cycles - 21 (+5)
Heat cycles at 'welding' - 19 (+3)
Cycles by hand - 12
Cycles using press or air hammer - 9 (+5) *
Total elapsed time - 2 1/2 hours *

* These two numbers are significant in relating the use of modern powered equipment to historic practice, working with human muscles alone. If strikers using sledges were employed, there would still certainly be some increase in number of working cycles / time expended. (Guestimate - increase by 30 % or more.) Starting with a 1.2 kg mass, it certainly would be possible for an individual to have worked these processes alone. (Guestimate - increase by x 4 - x 6 work cycles)


Resulting 'block', top and bottom surfaces

The 'block' at this point is still not completely refined. At this point the weight is 957 gm. Size is 16 x 4.5 x 2 cm. You can see that there is a major crack that runs into the bottom side about the mid line, about 3 mm deep.
The next step will be cutting along the crack, then adjusting the two pieces to the same width and length. At that point they will be welded up again, then drawn out slightly to ensure there are no more major flaws.

At this point:
Bloom to block loss = 25%
Ore to block yield = 13.5%

Hopefully the resulting billet will be compacted concisely enough that it can then go on to the final sequence - forging an actual replica of the axe-hammer. The billet is roughly the right size / volume for making one of these  objects.

One of the important observations here is the huge amount of effort - and overall losses, involved in producing a working bar for the blacksmith's hands in historic times. Besides the obvious use of power tools, an important difference is the use of rock coal instead of the historic charcoal as the fuel.

This should make us think differently about the value of those objects created by ancient smiths!

For more details on the Turf to Tools project (several photo essays and commentaries) :
http://warehamforgeblog.blogspot.ca/2014/06/scottish-dark-ages-iron-smelt.html
http://warehamforgeblog.blogspot.ca/2014/05/some-considerations-on-iron-ore-for.html
http://warehamforgeblog.blogspot.ca/2014/06/pictish-late-iron-age-smelt-overview.html

For information on the Scottish Sculpture Workshop
http://www.ssw.org.uk/

Saturday, June 28, 2014

Canada Day DEMO...

... at the GRIMSBY MUSEUM


I will be undertaking a 'Pioneer Blacksmith' demonstration as part of the Canada Day events at the Grimsby Museum.

Museum open on Canada Day : 10:00 a.m. to 3:00 p.m.
Demonstration Period :  11 am to 2 pm (likely extended)

 

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

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