Replies

1. 
   joinerswork | Dec 02, 2008 01:22am | #1

   swifty,

   My understanding (I'm no metallurgist) is that the term cast steel means that the tool has been forged from steel that was bought as an ingot that was cast at a foundry.  People may think that the term means the tool itself was made as a casting, (like cast iron items are made), but as I understand it, it was supposed to be an indication of a uniform, consistant alloy, steel throughout, as opposed to a lamination of steel to an iron body, or a case-hardened surface.

   Ray

1. 
   AdamCherubini | Dec 03, 2008 08:03pm | #4

   'but as I understand it, it was supposed to be an indication of a uniform, consistant alloy, steel throughout, as opposed to a lamination of steel to an iron body, or a case-hardened surface."

   That's sorta right, Ray.  David's got it right.  They took the blister steel, which was high carbon on the outside, low carbon on the inside, and folded it over to make the center a bit more homogeneous.  They called this shear steel.  If they folded it twice, they called it "double shear" steel.  This process is a type of lamination.  It's how and why Japanese sword makers did what they did.  The goal was to take a material that was not homogenous and make it more homogenous. 

   There's no inherent advantage to this, though there are some interesting and sometimes beneficial side effects.  This is simply what one must do when they don't have access to the superuior homogenous steels like cast steel.  This is most certainly NOT what modern Japanese chisel makers are doing.  They use beautifully clean very high carbon tool steels made in small quantities.  These come in different paper wrappers from Hitachi or some other steel producer, the color of which gives the steel it's name "blue steel", "white steel" etc.  That's the color of the wrapper and has nothing to do with the color of the steel.  I think the wrappers do indicate carbon content.

   The reason this is subject is so confusing is that there is another "lamination" involved.  Japanese as well as Western tool makers traditionally laminated steel to bodies of softer (cheaper) wrought iron.  They did this principally to save the cost of the steel.  Wrought iron is also easier to forge and weld. The English sometimes called these "lined" or "laid" tools.  And that's helpful as it distinguishes between a "laminated" shear steel and the forge weld lamination between steel and an iron body (lined/laid).  So when folls start talking about laminated tools, we need to know what lamination they are talking about.  It seems to me the Japanese mean "laid" but they often evoke the imagery of the other kind when they reference sword makers and the two are NOT similar. 

   The Japanese DO currently "line" their tools.  Some claim performance advantages for this.  I don't know of any Western makers doing this.  The stamp "Cast steel" on an old tool indicates the steel is crucible steel as David has rightly explained, as opposed to blister, shear, german steel etc.  It DOESN'T indicate a lamination.  I have solid cast steel chisels and "lined" cast steel chisels.

   Adam

2. 
   roc | Dec 03, 2008 10:32am | #2

   An explanation of " cast steel " in this context can be found in the book by Garrett Hack titled The Handplane Book. See page 45. In theory you have some high quality steel in your old chisels. I have no experience with this other than what I have read. I hope someone else will jump in here.

   How do you find they compare to modern high end chisels?
   How do you find they compare to Japanese laminated chisels?

   roc

   
   

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   Edited 12/3/2008 2:33 am by roc

3. 
   DCarr10760 | Dec 03, 2008 06:50pm | #3

   Heck, I'll take a stab at it and will be likely wrong enough that some really knowledgeable person will correct me, and we'll all learn.

   Before cast steel was developed (late 1700's?), steel was made by interleaving wrought iron with charcoal, heating it to a critical temperature for a long time in the absence of oxygen, allowing some percentage of carbon to migrate into the iron bringing it up to the required carbon content to make steel.  What you end up with looks all blistery (hence the name).  Depending on how tightly controlled the process is and the phase of the moon, the resulting steel may not be particularly homogenious in its carbon content. 

   To deal with this and make useable blades, the blister steel had to be repeatedly forged to both work out impurities and make the steel more consistant in terms of its crystalline structure and its carbon content.  So the quality of the steel was determined by the skill of the workers who made it.  I think that fine Japanese steel is still made this way (but I'm not sure).

   Cast steel (also known as crucible steel) takes blister steel and melts it in a crucible, which allows impurities to be more easily separated out and makes the carbon content consistant throughout the batch.  It is cast into ingots or bars for later working.

   I'm not sure that just because a tool says "Cast Steel" that it assures one of high quality since how the tool was forged, hardened and tempered has a lot to do with its edgeholding ability.  What has happened along the way to an old tool before it got into your hands will have an impact as well.

   Cast steel as a manufacturing practice gave way to the Bessemer process which I know even less about.

   Ducking and running,

   David

   
   

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   Edited 12/3/2008 10:52 am ET by DCarr10760