why taper square?

[bikecopXXX]

that's how i was "trained" and that's what i do.

 

as far as the reason why, i've heard:

1. tapering round gives you a spiral shape, hard to keep straight
2. tapering square helps visualize the taper & progress as the taper is forged
3. the end of the bar tends to split if you taper round

Got any more? 

[GNJC]

Tapering a triangle section is really hard...

[Dan C]

Seems to move the metal more efficiently.

[ThomasPowers]

Probably dating back to the WI days but tapering on the SQ you are always pushing the metal together.  Tapering on the round used to promote cracking around the axis as you were putting stuff in shear.

[bikecopXXX]

Thomas, what are the "WI days"?

[Dan C]

wrought iron

[bikecopXXX]

Tapering a triangle section is really hard...

that reminds me, i need a 60 degree V swage block...good project

wrought iron

i thought maybe me meant to type WWI as in the great war.

[GNJC]

Joking apart, I once made a three sided reamer for a friend and I am still ignorant of any way to taper a triangle easily other than grinding it. I have used the 60 degree grooves in a swage block for making triangle section on a couple of progects, but trying to taper by using progressively smaller grooves didn't work well, or at all, just created steps ... any advice on this would be welcome .

[the iron dwarf]

cut a tapered groove and as you hammer feed the work along it turning frequently

[GNJC]

Thanks for that Dwarf, a good plan.

[rockstar.esq]

Iron Dwarf,  Could you elaborate some more?  What is the parent stock shape and how are you hammering it with respect to the tapered groove.

 

Thanks,

[Francis Trez Cole]

It is easier to taper square because that is the way the molecules want to be. Iron likes to form very little cubes when it is hot in the austenite stage they can be moved a round. It is better to make a long square taper and then knock off the corners off making it 8 sided then do the process again making it 16 sided. for all purposes that is close to round. Trying to forge round at first leads to problems the molecules just do not want to go that way. You can get ripples and the will fold over causing cold shunts.

[SoCal Dave]

Francis:  wow, I've never heard the reason for tapering square was to coordinate with the shape of the molecules.  I've seen diagrams of body centered cubic structures, and face centered cubes, but that is at the atomic level.  When viewing the structures from a microscope, they look like the shapes of different sized cells, irregular in shape.  I'll have to think about that.  

[thingmaker3]

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.

[Charles R. Stevens]

As to your three sided taper, taper square, then round it. Now make it triangualar. Still going to grind it to finish, but that should get you close. You can even fuller it have to tack to rods on a plate) and refine the edges. Tho a for fluted reamer works well if fullerd

[AndrewOC]

'why taper square?'

Think of a sausage / stick/ bar of clay or plasticine. 

You want it to be a smaller size.

If you squash, turn, squash, turn... (which is 'rolling it' while forging) you are in effect twisting it.

By doing the CORRECT, Square - Octogan - Round, steps you are 'boxing-in' the material on the outside while allowing the length to grow= smaller cross section size. 

Hope that helps,

A.

[swedefiddle]

Drawing out a section to make a smaller section (whether tapered or not), it is best to go square because that is how our body moves best. A quarter turn of the wrist does not hurt the body, to make square section.  It is easier for our eyes to see the progress and adjust for control.

 

$0.02 :)

 

Neil

[patrick]

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.

[VaughnT]

Let's not forget that it maximizes the deformation of the metal due to the minimal surface area resisting the hammer's blow.

[JNewman]

I have had piping occur ( a crack up the center of a bar)  when I got sloppy and after rounding up a bar I continued to draw it down round.  

 

I do find drawing down hex works well for round tapers. 

[Ten Hammers]

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. 

[Frank Turley]

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"

 

Sayings and Cornpone

"Closed mouth gathers no feet."

[Francis Trez Cole]

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

[thingmaker3]

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

[Judson Yaggy]

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.