Sunday, January 27, 2013

Hammers - Weights, Styles - and Rounding Type

The core here started from a series of postings on 'Iron Smelters of the World' on Facebook
Eric Campbell wrote :
If you watch people with heavier hammer tend to grab the handle closer to the head of the hammer. Moving steel is all about the equation Kinetic energy = 1/2 mass times velocity squared what this boils down to is that if I double the mass I double the kinetic energy. If I double the velocity I can quadruple the kinetic energy. Many of the smiths that come from the Yellin line use lighter hammers that measure in length from the crook of their arm with the head of the hammer resting on the tips of their fingers. I've tried it and I can generate an astounding amount of kinetic energy that way however I like a bit more control so I tend to have my handles about 2-3 three inches shorter than that and I like having one of my faces being ground to be like a rounding hammer when I am doing long draws. (Brian) Brazeal tends towards a short handle and a rounding hammer this video is worth a watch if you do a lot of long tapers.

... I became aware that the hammer weight conversation is missing 4 variables. Face geometry, handle length. grip, and swing style.
1) Eric is echoing my own experience. Less mass, moved further and faster, equals more impact energy. I have seen Brian Brazeal working - massive hammer, moved very slow, short strokes. I suggest that a lighter hammer allows for more precise control, not only of target, but also of entry angle of the face, more importantly the edges.

2) Never forget the physical dynamics of body build! Personally, I have extremely long arms, and still after over 30 years of smithing, still only weigh 160 lbs over my 5 foot 11 frame. Brazeal is heavy through the chest, with much shorter arms and is very powerful in build. Not a surprise he would work in close, short, heavy, and pretty much punch - rather than swing the hammer as I do.

3) Something to direct this back to our topic of forging blooms: A lighter hammer, moving fast, does have more impact energy. But that energy will tend to be concentrated to the surface of the metal. For bloom welding (or thick bars) a heavier hammer moving slower will *penetrate* the force through the mass of the bloom. Remember that this is effect desired to compact or weld a bloom
Replica Viking Age hammers - Lower left based on Mastermyr at 800 gms
4) We all have to remember as well our bloom iron and antique wrought iron *does* move differently under the hammer stroke than modern steel alloys, often very differently. Those ancient smiths were not fools, and would be building hammers suited to their metal, anvils, and objects to be formed. It may suggest something that the kind of heavy sledges typical in contemporary blacksmith shops are absent from the early historical artifacts?


Why Use a Rounding Hammer
Brian Brazeal demonstrates and explains why a rounding hammer is the most versatile hammer to forge with.

1) Note that this is work with COPPER - not STEEL.
Copper moves like butter when hot, and even cold, moves about the same as mild steel would if it was at forging temperature. This gives a false impression of the effectiveness of the hammer technique. Copper, unlike iron, can be effectively cold worked (for a good while before work hardening).

2) A short stroke with a heavy hammer?
Note that Brazeal is noticeably out of breath, even after the first hammer sequence. This despite how slow the pace of the individual strokes is (also an effect of the use of a very heavy hammer.) Perhaps not the ideal method if you intend on any actual production work?  (Of course, you might be younger and more fit!) This method suits a physical build with a barrel chest and massive chest muscles, short arms with 'Popeye'  chunky arm muscles - all suited for power.
Definately not a weight or style for those with lighter builds, longer arms, and more slender 'dancers' muscles - suited for speed.
Note also how he is choking up on the handle, gripping the hammer just barely back of the head. There is no swing involved here at all - he virtually is punching up and down in a straight line.

3) Entry Angle?
Note that Brazeal is working his strokes at 90 degrees to the length of the bar. This puts the line of force *across* the desired direction of the taper - not *down* it. Although care is being used to keep the hammer flat and straight, the natural dynamic of your body will cause some of the material being forged to be pushed sideways if you work as shown. If you are

3) Cheating on the Edges!
Note that the effects attributed to the rounding hammer are as much because of the use of both the curved base of the horn - and the use of the front and back edges. Although the slight curve of the rounding hammer *does* increase the speed, this is secondary to the much more aggressive pinching by curved horn and especially the edge radius.

4) Straightening with a Round face?
No, Use the FLAT side of the hammer for straightening! That *is* what the second face on the hammer is for after all.
Note he specifically says : "I think stems look a bit better rough than they would perfect." This then is a *design choice* not a technical method. Using the rounding face when finishing the taper into round will certainly leave the surface facetted.

Near the end of the video, he talks about 'not hitting square' with a flat face. Sorry, I see this as a flaw in basic technique. How could you be so aware of the entry angles available to the crowned surface, but at the same time so sloppy with the flat?

5) The true advantage of the Rounding Hammer?
Is seen over the second part of the forming - the pulling out of the tip into the leaf shape.
Again, this will *not* be so dramatic an effect if forging steel. In steel, as the material thins, it will loose heat faster and faster - to the point where it will prove almost impossible to work the material before it cools in contact with the anvil - and becomes brittle.

OABA had flown Brian Brazeal up at considerable expense for a two day workshop. There was an afternoon demonstration session, which I attended. My apprentice Kelly Probyn-Smith, who stands all of about 4 foot 8, found the methods demonstrated completely outside of her physical abilities. Despite my lifetime of blacksmithing, I also would not be able to utilize the physical methods illustrated.

Remember blacksmithing is a *physical* activity. The way any individual should chose to work should be first determined by the safest, most comfortable and most effective system as defined by their individual body dynamics.

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

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