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why taper square?


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#21 Ten Hammers

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Posted 16 February 2014 - 11:02 AM

Some will disagree.  The quality of the steel will make a difference.  The first heat (bloody hot for my choices ) will make large difference.  Drawing square ( rotating 45º back and forth ) taper rather fast and gaining heat on the tip       (this on the far side and distal end off the edge) will be the best way for me.  Perhaps leave the end not really sharp before going back to the start of the taper to start rounding.  JNewman has my thoughts by hex first but honestly sometimes this process happens pretty fast and my head says " just keep it under control ".  This means don't let it split and keep it smooth.  Most days this works well.  Some days you the coyote, some days the post.  Drawing on the power hammer may be a bit different.  Drawing round will make a spiral and this can be rotated either way to correct it.

 

Regardless, the start of the drawing to taper for me should be with a pinch past the far side and striking ON the far side.  This creates a bit of a knob with a taper behind it.  This knob can then be drawn in a couple of blows to create the initial point.  Pointing 5/8 or 3/4 rod for tripod ends is accomplished in one heat this way.  No need in that issue to round afterwords because all you are doing is sharpening the end.  We all have different wants and needs.  I find these things I have described tough to do in gas forge for the large part.  Gas excels in other areas. 


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#22 Frank Turley

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Posted 16 February 2014 - 11:49 AM

Well geez, you need a point of reference. If it's a square tapered section with straight sides, you have your point of reference from which to make the bar octagonal and round. If you're just rotating and hitting, you're working helter skelter, hoping you'll have a nice round taper some day. No point of reference.

 

As for pipe, I think Schwarzkopf mentions this briefly in his book.* As I recall, the example showed flattening a round bar in one dimension resulting in an Rx capsule cross-section. For your next blows, if you only turn it, say, 60 degrees instead of 90, you have lost your full basal support on the anvil. In addition, your hammer is not hitting it fair and square. One or more blows could cause an internal rupture.

 

*Ernst Schwarzkopf, "Plain and Ornamental Forging"

 

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#23 Francis Trez Cole

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Posted 16 February 2014 - 03:02 PM

The only molecules in steel are carbides and inclusions. It is the crystal lattice within each grain which is cubic. And that lattice is randomly oriented within each grain.



On the crystal lattice it starts as a cube then a pine tree shape comes from the center of each side of the cube this is called a dendrite that is the uneven growth. Reference Welding Metallurgy written by Henry and Claussen
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#24 thingmaker3

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Posted 16 February 2014 - 04:44 PM

The dendrites are composed of atoms in a cubic lattice. Reference the book cited in post above.
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#25 Judson Yaggy

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Posted 16 February 2014 - 05:50 PM

The crystal structure of iron has nothing to do with why you taper in a square form. You'd use the same process with any other metal, regardless of crystal structure. The reason for tapering a square is because it is the most efficient method. if you are forging a square, you fully contact the work on two sides (hammer and anvil) with each blow, leaving the two perpendicular sides unconstrained. If you tried to taper a round you'd have to deliver considerably more blows per unit of length since you have to work your way evenly around the circumference. For example, for forge an octagon requires 4 blows, while a square only requires 2. A sixteen sided shaper would require 8 blows and so on.

A metalurgist working in industry probably knows more about crystal structure and atomic details than the rest of us put together.  I'm going with what Patrick says.



#26 Francis Trez Cole

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Posted 16 February 2014 - 06:45 PM

The dendrites are composed of atoms in a cubic lattice. Reference the book cited in post above.


yes right its a cube thats square
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#27 thingmaker3

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Posted 16 February 2014 - 08:45 PM

...because the round cubes are just plain funny-lookin'
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#28 patrick

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Posted 16 February 2014 - 08:53 PM

Dendrites form during solidification and they are NOT square. A dendrite grows from a nucleation site and develops primary, secondary and tertiary arms. If you look at it with the aid of an SEM you will see that It actually looks a little bit like a fern or evergreen, which is where the word dendrite comes from. While it is true that the iron crystal lattice is cubic, that is on the atomic level. At larger scales, the arrangements are not cubic unless forced that way by deformation. As I noted in my earlier post, we forge square because that is the most efficient method and that has to do with constrained and unconstrained surfaces, not atomic structures. At the macro scale, iron has no particular tendancey to form cubes. It takes on the shape of the contain in which it solidifies and after that it takes on whatever shape it is forced into, whether square, round or some intricate configuration. That ability to be formed in some many ways into so many things is one of the reasons iron based alloys are so widely used.



#29 lupiphile

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Posted 18 February 2014 - 07:29 AM

Sub atomics aside, as has been alluded to before, but perhaps not stated directly, is that by forging square you're forging though the center line of the stock. any force applied to the stock not through the center line, when drawing down has a shearing effect ( the piping Mr.Newman referred to)  and will tear your metal apart eventually. This is also why drawing down hex works.It's all about the center line. You could draw down a 16 sided object if you had perfect registration and worked evenly, but that would take much longer to do well than the usual, square, octagon, round. Take care, Matt

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#30 Gerald Boggs

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Posted 18 February 2014 - 10:14 AM

Sub atomics aside, as has been alluded to before, but perhaps not stated directly, is that by forging square you're forging though the center line of the stock. any force applied to the stock not through the center line, when drawing down has a shearing effect ( the piping Mr.Newman referred to)  and will tear your metal apart eventually. This is also why drawing down hex works.It's all about the center line. You could draw down a 16 sided object if you had perfect registration and worked evenly, but that would take much longer to do well than the usual, square, octagon, round. Take care, Matt

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#31 ThomasPowers

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Posted 18 February 2014 - 12:26 PM

Here I thought we did square cause most of us can count that high!  (and on the fingers of one hand even if a couple of them are a bit odd looking.)

 

May I mention that Patrick is not only a metallurgist in industry he works for a FORGING company to boot!


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#32 Charles R. Stevens

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Posted 18 February 2014 - 12:40 PM

So that's my problem, I get lost around 3...
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#33 yahoo2

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Posted 18 February 2014 - 06:27 PM

So if I were to pick and chose the bits that I like from all the previous posts, I come up with this

 

1. drawing down square gives me a easy and predictable reference (gauge) for the amount of taper I am achieving as I work.

2. I am moving the mass mostly in only one direction perpendicular to the hammer (as opposed to spreading it like a pancake) avoiding the shearing effect.

3. the square shape lets me deform the whole profile of the metal not just smear the top and leave the centre relatively untouched.

4. the total number of hammer blows is reduced as the fuller then flatten technique of drawing keeps the square shape without (too many) extra correction hammer blows.

 

Is that a fair summary or have I missed the mark completely?


 I'm confused, no wait... maybe I'm not..


#34 Francis Trez Cole

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Posted 19 February 2014 - 06:46 PM

I think you got it.
Longfellow:
His brow is wet with honest sweat,
He earns whate'er he can,
And looks the whole world in the face,
For he owes not any man.

#35 CleetisMorgan

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Posted 20 February 2014 - 06:42 AM

Another reason to love IFI--this thread sent me to school and I didn't have to pay tuition...




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