Sunday, April 08, 2018

Use a Bigger Hammer…


... or maybe NOT

part 4 on the ‘Hammers & Hammering’ series (c)

One of the biggest mistakes I see with new (and not so new) blacksmiths is a tendency to ‘use the biggest hammer’. (a)
Unfortunately, is is often the result of completely incorrect cultural stereotypes, mixed with what is basically ‘macho BS’.

* It does not matter how hard you HIT - if you just MISS. *

I am going to attempt to interject some logic - and basic science, into this commentary.
As you will see, there are a large number of factors effecting the ‘most effective’ production of hammer force into a specific forging operation. *Biggest* may not be *best*.

1) Input Energy
Any given individual will be limited to how much physical muscle energy they can apply into moving a hammer. This will be determined by raw body size, muscle strength, physical fitness.
- Generally, the larger the person, the greater the potential amount of muscle energy available.
- However, mere *size* may not prove more important than *fitness*.
Critically important - *Energy input is effected by other variables beyond simple muscle size.*

2) Deforming Force
Any metal bar will require a certain amount of force applied to it (Energy) before it will start to deform. - The larger the diameter of the bar = the greater the resistance to changing shape.
R ~ d
- The higher the temperature of the metal, the lower the resistance to changing shape.
R ~ T
So remember you could apply more energy (hammer force) or just increase the temperature of the bar, especially important when working thick bars.
You also see that as a bar cools, its resistance will increase. At a certain temperature point (with the hammer force consistent) you will not be overcoming the resistance, effectively accomplishing nothing.
(We are avoiding the major problem of continuing to attempt to work a bar ‘below critical’, so no longer at its ‘plastic’ state.)

3) Work
Given above, how many individual hammer stokes are applied in one ‘heat cycle’ may prove as important (if not more) than the energy of any single stroke.
W = E x f ~ R
You can see that this also needs to be related back to overcoming the bar’s resistance.

4) Energy
How is Energy (force as applied to the bar) produced?
Energy is the mass (of hammer) times the velocity (speed of the hammer) *squared* all divided by a half
E = (m x v2) x 1/2
What this should be showing you is that you actually create *significantly* more energy by moving the hammer *faster* - than by using a heavier hammer, moving slow (!). Typically, a longer swing will increase the speed of any individual hammer stoke.

5) Control
Once a mass is in motion, it will require force applied to change that motion (overcoming inertia). Both increased hammer weight and increased hammer speed are factors.
F = m x (∆ v x t)
In practice, you will find it requires more energy to change a heavy hammer, moving slow, than a lighter hammer, moving fast. This because even a small shift at the start of a swing can make a large difference in strike position over the length of that swing.

6) ‘Penetration’
Now, from above you can see the factors that effect the creation of the raw energy applied to a bar for a forging step.
Beyond the resistance to changing shape at all, there is also an ‘impact effect’ - the penetration of force into the bar. (There may be math for this, but a casual search did not yield anything not terribly complex.) A lighter hammer, moving fast, will effect the metal differently than a heavy hammer, moving slow - even though the energy involved may be identical.
The bar has ‘inertia’, that ‘resistance to changing shape’.
Consider this analogy :
You have a choice between taking a fist strike from either Bruce Lee, or Muhammad Ali.
Bruce Lee gives you a light fist, but moving extremely fast. The result is that your jaw is shoved back faster than your head can move. Result is a shattered jaw, and down you go.
Muhammad Ali gives you a heavy blow, moving (relatively) slower. Result is your whole head rocks back, sloshing your brain unconscious, and down you go.
Similarly:
A light hammer, moving fast, will impact and move the *surface* of the bar. The net result is a T shaped distortion of the bar. This effect most pronounced working the edges of tall, thin bars.
A heavy hammer, moving slow, will impact and shift the entire mass of the bar. The net result is a squashed barrel shaped distortion. This effect most pronounced on square bars.

Conclusion:

You may start to see there that there is a clear relationship between the choice of hammer (both weight and handle) and body type. Obviously, a heavy hammer is not always the ideal.

Most typically, those with ‘barrel’ body builds and heavy joints and short arms, may chose for purely mechanical reasons, to work with heavier hammers, using shorter strokes. in contrast, those with lighter builds, with thinner joints and longer arm linkages, are better suited to using lighter hammer weights and much longer strokes. (b)

You can see clearly that hammer *speed* is a greater energy producer than hammer *weight*. For this reason anyone ‘choking up’ on the hammer handle is not using the tool efficiently. (Short ‘club’ handles obviously a bad choice).

- The easiest way to increase effective hammer impact is merely to use the entire handle length.
- Simply raising the hammer higher on each stroke will significantly increase impact energy. This with less actual muscle force required than by using a heavier tool.
- Increasing the strokes per minute will also obviously both quickly and easily improve the amount accomplished per heat cycle.
- A lighter hammer is always easier to control. Do consider roughing out with a heavier tool, then switching over to a lighter tool for surface finishing.


Symbol Definitions

d     is ‘diameter’, here the measurement at right angles to direction of forming
E     is ‘energy’
f    is ‘frequency’, here the number of hammer stokes (per minute or heat cycle)
R     is ‘resistance to deforming’
T    is ‘temperature’
t     is ‘time’
v     is ‘velocity’, here the speed the hammer is moving
W    is ‘work’, here the amount accomplished (per minute or heat cycle)
~     is ‘varies with’ (note this not the correct symbol, not on my keyboard)
∆    is ‘change in’

(a) I have repeatedly heard any number of  feature demonstrators remark about ‘how much my elbow hurts’. At the same time observing them using not only hammers obviously too heavy for them to correctly control. Or using very poor technique. Usually both.

(b) One of the trends over the last decade particularly has been to ‘celebrity’ blacksmith demonstrators - with ‘named designed’ hammers. New blacksmiths have proven especially susceptible to mimicking these methods. In my experience often not understanding the clear relationship between not only effective, but actually *safe*, selection of tools and physical technique based on body type. There is a reason there are so many hammer styles - this must remain a purely personal choice!


(c) Others in this series
2018/02/getting-hammered.html
2018/03/getting-hammered-2-dynamics.html
2018/03/getting-hammered-3-setting-up.html
Earlier commentaries
2013/01/hammers-weights-styles-and-rounding-type.html
2014/07/a-bit-about-hammers.html
2016/08/getting-hammered.html
2016/08/more-on-hammers.html

Friday, March 30, 2018

Viking Age Ring Headed Pins

I have just finished a small order for a pair of replica Ring Headed Pins.
These are destined for Mystic Seaport, part of an upcoming special exhibit:

Science, Myth, and Mystery: The Vinland Map Saga
May 19, 2018-September 30, 2018
R.J. Schaefer Gallery


Replicas - click for expanded view
Replicas - Life Size (10cm)
(Resin Copy of) Vinland Pin : as seen for 'Full Circle - First Contact' (1)
Vinland Ring Pin (artifact)
Of interest may be this sample:

click for expanded view
Life sized = about 20 cm
This third object is an artifact on display at the National Museum of Scotland, Edinburgh (photograph taken August 2017). It was described as 'Bronze Ring Pin, found in Christianized Viking Burial' (no date given)
In addition to the much greater size, the head is more of a flattened square, with the attachment loop at right angles to the thinner dimension. The difference between the upper cylindrical and lower tapered square cross sections is less pronounced than the Vinland artifact.

These ring headed pins are found widely through Norse Scotland, Ireland and in Iceland. The general dating is around 1000 AD.

This makes the finding of the single bronze pin at L'Anse aux Meadows significant. It is the single object that not only places the occupation to Norse, but also to the late Viking Age. This dating was already suggested by the chronology of the Sagas describing the voyages to Vinland - but also matched closely the carbon 14 dates provided from wood samples at the same layer.


Mystic Seaport will also be hosting  :

The Vikings Begin

Treasures from Uppsala University, Sweden

May 19 - September 30



1) Photo Credit = 'McArey' (via internet search)
http://www.angelfire.com/nf/mcarey/fullcircle/LAM.html
Note that that web site contains an almost complete visual record of the objects from L'Anse aux Meadows seen in the 2000 exhibit 'Full Circle - First Contact'


Note : At time of writing, I remain uncertain if  'The Vikings Begin' is the next showing of an exhibit currently touring North America. Originally titled 'They Call Them VIKINGS', it was created by the Swedish History Museum. The Royal Ontario Museum in Toronto was the most recent showing (November 4, 2017 - April 2, 2018).
I have had three occasions to view that specific exhibit (also working as a costumed interpreter at the ROM opening weekend). 
One of the major problems with the presentation is that there is none of the normal supporting documentation available. There is nothing on the SHM web site, there is no exhibit catalogue available.
A second problem is that this exhibit has changed its title at almost every hosting institution mounting it.

Friday, March 16, 2018

Seeking the 'Three Wise Men'...

Knowledge / Skill / Experience


This commentary is framed up against a number of similar first contact requests and questions I've had over the last month (especially).
"My 12 year old (son) has been watching 'Forged in Fire' and is keen to learn blacksmithing. Is there a one day course you teach?"
Or some variation on this theme.

No. No. No.

Right off:
Go and read 'Teens as Students'
then come back to the rest of this...


Knowledge can be had through study.

'Extensive research' is often suggested - this most commonly stated as 'hours spent on YouTube'. You watch 'Forged in Fire'? See my commentaries on that mess.
Problem there is complete lack of 'peer review' and commonly no attempt at all at to indicate the background of the presenter. Everyone is an 'expert', even if they don't actually have a clue! Status is indicated by 'click views' - not by actual achievement level.
(I went to YouTube, and did a general search using 'blacksmith knife' *)



See the title? FORGE a knife.
• The illustration of the forging process is only the first 5 minutes of a 25 minute video.
• The forging process illustrated are not so much wrong - as poorly carried out.
• The hammer technique used is horrible. Too heavy a hammer, grip choked up as a result. Thumb on top of the handle (will lead to tendon damage).
• The heat treating is effectively minimal, certainly not 'best practice'.


Ok, the presenter is attempting to simplify, de-mystify, encourage...
But :
• Briquettes are not the same as charcoal.
• Scrap wood will not produce effective forging temperatures
• Sure, you could use a small piece of scrap plate. Or a rock.
The core purpose of an anvil is *flat* and *stable*. None of the alternatives suggested are effective (even if that small plate had been bolted down to a wood stump - it would have been massively more effective!)
• A woodworking claw hammer? Seriously??
Sure, you *could*. (In Africa, I've seen video of using a fist sized rock as a hammer!)
There is a *reason* metalworking hammers are a different shape. ** 
• "I've only been forging for about 6 months"
Draw your own conclusion...

My overall recommendation:
• Do not start inside YouTube.
• Go to accomplished blacksmith's personal web sites.
See what kind of work they are able to create. How long they have been involved.
Find those with practical experience, proven ability : then look for those who may include tutorials.
• See recommendations on effective reference books for the novice blacksmith


Skill and Experience are somewhat linked.
But they are not exactly the same thing.

Skill is developed though simple repetition.
You have to do the thing, to become any good at the thing. Make 100 long points - and you will become effective at making long points.
Now just how fast a given individual will become effective at a physical task can vary a lot between individuals. Consider how long it took you to learn to ride a bike, or accurately throw a ball.

Experience is a wee bit different.
This is the 'well, that worked a lot better' factor. I can tell students that digging in the front of the hammer while making points will speed the process. How much to increase speed, but also not so much that you create creases you have trouble removing? Just exactly which hammer style and weight works best for you - for which forming step? An individual has to just get the feel for all this for themselves.


I normally suggest the most effective way for a new smith to progress is :
• take a basic course - by a well experienced instructor ***
(so you have some clue to what this is about and how to start)
• get simple working tools set up at home
•practice
• take another weekend course
• practice
• repeat, repeat





* Lest you think I am attempting to pick on specific individuals, these are the very first selections presented on the defined search.

** In the Royal Ontario Museum (Toronto) is an early Egyptian hammer for metalworking gold or copper. It is a square face with a cross peen, about the same size as the hammers I have in my shop. Date is roughly 3000 BC (predates human iron by at least 1000 years!)

*** Inside Ontario, there are three individuals who each have been teaching since the mid 1980's - and who continue to offer a range of weekend courses:
Obviously myself (!) at the Wareham Forge
David Robertson (www.artistblacksmith.com).
Robb Martin (www.thak.ca)
Both the others are also excellent teachers, and will approaches their programs (and content) a bit differently. Also a differnent range of scheduled dates that will give more options.

Tuesday, March 13, 2018

AIR HAMMER for SALE

 SOLD!


I am upgrading my own air hammer to a heavier weight, both built by David Robertson of Hammer & Tongs Studio. (go here for description)

To that end, I (HAVE SOLD) my current air hammer (Imperial measurements) :

50 lb head weight
• built on ABANA 'lift / drop' system (by R. Kinyon)
• requires separate (larger) compressor


This video shows me working on railing elements using this air hammer

This hammer is 'rated' for working up 1 1/2 x 1 1/2 inch stock.
I have worked material as large as 1 1/2 x 4 (admittedly - slowly!)

click for larger views for all images

Side view
3/4 view
front view
• Base plate = 30 deep x 22 wide• Total frame height = 88
• Total weight (approximate) 450 lbs

Closer view of working area - plastic safety shield down
- working height = 33 1/2 (floor to top of lower die)
- throat clearance = 12  (back edge of die to frame gap)
- die size = 3 1/2 x 1 1/2
- total stroke height = 9 inches
(note effective working gap between the dies is really about 4 inches)

close up of the die set up
The dies are currently set up with the bottom die having the rear half with rounded edges (to act more effectively for drawing out) See the close up image.

- head block = 4 x 4 x 10 inches
- cylinder type = heavy duty hydraulic (replaced the original lighter duty air type)
- cylinder shaft diameter = 1
- cylinder interior diameter = 2
- supply hose length = 5 feet (as existing - from compressor)
- foot peddle type control, on roughly 4 foot hose (to allow for standing back when working longer bars)

Includes:


- input air control (water trap, gauge, oiler)
- full air lines (compressor to hammer)


additional die blocks made to fit this machine:
- 'Hoffi' style bottom 1/2 crown die (for spreading, seen used above)
- centre mount 'hardie hole' die block for one inch (would allow use of existing anvil hardie tools)
- centre shaft bottom die to front hardie hole (fits above)
- bolt in place front hardie hole attachment

This machine is basically 'plug and play' - fully working and ready to go.

- Requires a larger (40 gallon / 2 HP) air compressor for input air
- Air flow required is 10 cu/ft/min @ 90 PSI

It may be possible to take some of the pieces apart. Originally the bottom die block section bolted into place. This has been re-enforced with some welding - which likely could be separated with an angle grinder / zip disk. This support is made of two pieces of square tube, which I had filled with lead shot to improve the stability of the machine.

I have the machine mounted on a raft made of 4 lengths of rail tie, each four foot long. This sitting on top of four inches of sand. (All dug in to ground level).

SOLD!!

(posting retained for history!)
 

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

COPYRIGHT NOTICE - All posted text and images @ Darrell Markewitz.
No duplication, in whole or in part, is permitted without the author's expressed written permission.
For a detailed copyright statement : go HERE